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SD 73-SA-0036 4 PART 2CONTRACT HAS 9-12909

GEOSYNCHRONOUSPLATFORM DEFINITION

STUDY CASE

Volume IV - Part 2 COPYTRAFFIC ANALYSIS AND SYSTEM

REQUIREMENTS FOR THENEW TRAFFIC MODEL

JUNE 1973

Space DivisionRockwell International

1 2 2 1 4 L a k e w o o d B o u l e v a r d

D o w n e y , C a l i f o r n i a 9 0 2 4 1

https://ntrs.nasa.gov/search.jsp?R=19730020132 2020-07-10T15:09:20+00:00Z

CONTRACT MAS 9-12909 SO 73-SA-0036-4 PART 2

GEOSYNCHRONOUSPLATFORM DEFINITION

STUDY

Volume IV - Part 2TRAFFIC ANALYSIS AND SYSTEM

REQUIREMENTS FOR THENEW TRAFFIC MODEL

H. L. MyersGPDS STUD Y MAN A GER

JUNE 1973

Space DivisionRockwell International

1 2 2 1 4 L a k e w o o d B o u l e v a r d

D o w n e y , C a l i f o r n i a 9 0 2 4 1

Page Intentionally Left Blank

Space DivisionNorth American Rockwell

FOREWORD

The Geosynchronous PI a't'forirr Definition Study'was a pre-Phase A analysisconducted by the Space Division of Rockwell International Corporation (Rockwell)under Contract NAS9-12909 for the Lyndon B. Johnson Space Center of theNational Aeronautics and Space Administration. The study explores the scopeof geosynchronous traffic, the needs and benefits of multifunction space plat-forms, transportation system interfaces, and the definition of representativeplatform conceptual designs. The work was administered under the technicaldirection of Mr. David Brown (Telephone 713-483-6321) of the Program PlanningOffice/Future Programs Division of the Lyndon B. Johnson Space Center.

This report consists of the following seven volumes:

Volume I - Executive SummaryVolume II - Overall Study SummaryVolume III - Geosynchronous Mission CharacteristicsVolume IV, Part 1 - Traffic Analysis and System

Reguirements for the Baseline TrafficModel

Volume IV, Part 2 - Traffic Analysis and SystemReguirements for the New Traffic ModelGeosynchronous Platform SynthesisVolume V -

Volume VI Geosynchronous Program Evaluation andRecommendations

Volume VII - Geosynchronous TransportationRequirements

SD 73-SA-0036-1

SD 73-SA-0036-2

SD 73-SA-0036-3

SD 73-SA-0036-4Part 1

SD 73-SA-0036-4Part 2

SD 73-SA-0036-5

SD 73-SA-0036-6

SD 73-SA-0036-7

Acknowledgement is given to the following individuals for their partici-pation in and contributions to the conduct of the study:

R. D. MestonL. R. HoganE. MehrbachDr. K. A. EhrickeM. R. SchallJ. W. PatrickE. L. TrimanE. G. CleggK. B. RobertsA. GianformaggioD. W. EarleR. E. OgelvieR. P. ArrasW. C. SchmillJ. B. WeddellE. F. Kraly

Mission and Program AnalysisSystems Engineering and Spacecraft DesignCommunications and AvionicsAdvanced Mission AnalysisOperations and Traffic AnalysisCrew Systems and Servicing AnalysisCommunicationsSpacecraft DesignOperations AnalysisCost AnalysisSystem IntegrationGuidance and ControlThermal ControlElectrical PowerAstro-Physics ProgramsSensor Systems Analysis

- 111 -SU 73-SA-0036-4


CONTENTS

Section Page

1.0 INTRODUCTION . . 1-1

2.0 SUMMARY 2-1

NEW TRAFFIC MODEL . . 2-1GEOSYNCHRONOUS ORBIT SATURATION . . . . 2 - 5GEOSYNCHRONOUS REQUIREMENTS ASSESSMENT. . . 2-6

3.0 NEW TRAFFIC MODEL . 3-1

3.1 CANDIDATE USER ORIENTED FUNCTIONAL APPLICATIONS 3-3COMMUNICATIONS AND DATA . . . . . . 3-3SCIENCE AND APPLICATIONS . . .. .. . . . 3-5

3.2 U.S. DATA TRAFFIC FORECASTS(COMMUNICATIONS, SCIENCE AND APPLICATIONS) . 3-7EDUCATION 3-9COMMERCIAL BROADCAST . . . . . . . 3-9TELECONFERENCING 3-12TELEGRAPH . . 3-12POST OFFICE 3-14MEDICAL DATA BANK . . 3-14BANKING, BUSINESS, AND CREDIT TRANSACTIONS . 3-17NEWSPAPER 3-19ELECTRONIC PUBLISHING 3-19CIVIL DEFENSE 3-19WELFARE DATA BANK 3-21LIBRARY DATA BANK 3-23PRIVATE RECORD BANKS 3-23TELECOMPUTATIONS 3-26METEOROLOGY 3-29EARTH RESOURCES . . . 3-29NAVIGATION 3-29AIRCRAFT CONTROL 3-31COMMUNICATIONS AND SYSTEM TEST . . . . 3-33ASTRONOMY 3-35TRACKING AND DATA RELAY . . . . . . 3-36SOLAR ILLUMINATION . . . . . . . 3-36SPACE POWER RELAY 3-39

3.3 WORLD AREA USER REQUIREMENTS DEVELOPMENT . . 3-41COMMUNICATIONS AND DATA TRAFFIC . . . . 3-41INTERNATIONAL SCIENCE AND APPLICATIONS . . 3-48NATIONAL SPACE APPLICATIONS PROGRAM . . . 3-48

- V -

SD 73-SA-0036-4


Section Page

3.4 WORLD USER REQUIREMENTS BY FUNCTIONALSATELLITE TYPE : 3-51

INTERNATIONAL/DOMSAT TRAFFIC DISTRIBUTION . . 3-52INTERNATIONAL SATELLITE (INTELSAT) 3-57DOMESTIC SATELLITE (DOMSAT) 3-61METEOROLOGY AND EARTH RESOURCES SATELLITEMERSAT) 3-61

NAVIGATION AND AIRCRAFT CONTROL (NACSAT) . . 3-64APPLICATIONS TECHNOLOGY SATELLITE (ATS) . . 3-64ASTRONOMY SATELLITE 3-64TRACKING AND DATA RELAY SATELLITE (TORS) . . 3-64SOLAR ILLUMINATION SATELLITE 3-64POWER RELAY SATELLITE 3-69

3.5 FUNCTIONAL SATELLITE CHARACTERISTICS -,- . . . 3-79INTELSAT CHARACTERISTICS CRITERIA /: . . . 3-79

Earth Coverage . . 3-79Satellite Longitudinal Locations . . . 3-81Lifetime 3-81Data Rate Capability . 3-81Satellite Redundancy . . . . . . 3-81

DOMSAT CHARACTERISTICS CRITERIA . . . . 3-81Earth Coverage 3-81Satellite Longitudinal Location .,•>, . . . 3-81Lifetime 3-81Data Rate Capability 3-81Satellite Redundancy 3-82

MERSAT CHARACTERISTICS CRITERIA . . . . 3-82Earth Coverage 3-82Satellite Longitudinal Location . . . . 3-82Lifetime 3-82Data Rate Capacity 3-82Satellite Redundancy 3-82

NACSAT CHARACTERISTICS CRITERIA . . . . 3-82Earth Coverage 3-82Satellite Longitudinal Location . . . . 3-83Lifetime . 3-83Data Rate Capacity 3-83Satellite Redundancy 3-83

ATS CHARACTERISTICS CRITERIA 3-83Earth Coverage 3-83Satellite Longitudinal Location . . . . 3-83Lifetime 3-83Data Rate Capacity 3-84Satellite Redundancy 3-84

ASTRONOMY CHARACTERISTICS CRITERIA . . . 3-84Earth Coverage 3-84Satellite Longitudinal Location . . . . 3-84Lifetime 3-84Data Rate Capacity 3-84Satellite Redundancy 3-84

SD 73-SA-0036-4


Section Page

TORS CHARACTERISTICS CRITERIA 3-84Earth Coverage . .,.,,..• • ,.„•.•• • • • 3-84Satellite Longitudiriaf Locatiorvs . . . 3-85Lifetime 3-85Data Rate Capacity 3-85Satellite Redundancy 3-85

3.6 FUNCTIONAL SATELLITE LOCATIONS . . . . . 3-873.7 TRAFFIC MODEL SCHEDULES BY SATELLITE FUNCTIONS . 3-893.8 NEW TRAFFIC MODEL SUMMARIES . . . . . . 3-105

4.0 GEOSYNCHRONOUS ORBIT SATURATION 4-1

4.1 PHYSICAL CONTENTION ANALYSIS 4-3APPROACH ' ... 4-3SATELLITE CONGESTION EVALUATION . . . . 4- 3

4.2 EMI CONTENTION ANALYSIS 4-11SATELLITE R F CHARACTERISTICS . . . . . 4-11SATELLITE DISTRIBUTIONS BY FREQUENCY BAND . . 4-13EMI MODEL, CRITERIA AND ANALYSIS . . . . 4-13RECOMMENDED SOLUTIONS . . . . . . . 4-21

5 . 0 GEOSYNCHRONOUS REQUIREMENTS ASSESSMENT . . . . 5 - 1

5.1 SATELLITE INVENTORY ANALYSIS 5-3PROGRAMMATIC DESCRIPTIONS 5-3

Intelsat 5-3Domsat . . ... 5-4Mersat 5-4Nacsat . . . , . 5-5Advanced Technology Satellite (ATS) ... 5-5Astro-Physics . . 5-5Tracking and Data Relay Satellite (TDRS) . 5-6

SPACECRAFT CHARACTERISTICS 5-65.2 MISSION OBJECTIVES GROUPING 5-95.3 GEOSYNCHRONOUS PLATFORM REQUIREMENTS . . . 5-13

COMMON SUPPORT .MODULE 5-13DATA RELAY PLATFORMS . 5-13TRACKING AND DATA RELAY PLATFORMS . . . . 5-23OBSERVATIONAL PLATFORM REQUIREMENTS . . . 5-24NAVIGATION AND TRAFFIC CONTROL PLATFORMS . . 5-25

Functional Parameters 5-26Summary 5-27

5.4 ON-ORBIT SERVICING CRITERIA 5-29CONFIGURATIONAL REQUIREMENTS 5-29SUBSYSTEMS REQUIREMENTS . 5-29EVOLUTIONARY CONSIDERATIONS 5-30

SD 73-SA-0036-4


ILLUSTRATIONS

Figure Page

2.0-1 New Traffic Model Development Approach . . . . 2-22.0-2 Satellite Spacing Geometry . . . . .2-62.0-3 Zone 2 Satellite Distribution for The New Traffic

Model (1990) . . . . . . . . .2-73.0-1 Geosynchronous Platform Definition Study Logic . . . 3-23.2-1 Ratio of Satellite to Long Distance Information Traffic . 3-83.2-2 Education Function Demand Model for USA . . . . 3-103.2-3 Commercial Broadcast Function Demand Model for USA . . 3-113.2-4 Teleconference Function Demand Model for USA . . . 3 - 1 33.2-5 Postal Function Demand Model for USA .. . . . 3-153.2-6 Medical Data Bank Function Demand Model for USA . . 3 - 1 63.2-7 Banking, Business, and Credit Transaction Function

Demand Model for USA . . . . . 3-183.2-8 Newspaper Function Demand Model for USA .. . . 3-203.2-9 Civil Defense Function Demand Model for USA . . . 3-223.2-10 Welfare Data Bank Function Demand Model for USA . . . 3-243.2-11 Library Data Bank Function Demand Model for USA . . 3-253.2-12 Private Record Bank Function Demand Model for USA . . 3-273.2-13 Telecomputation Function Demand Model for USA . . . 3-283.2-14 Meteorology Function Demand Model for USA . . . 3-303.2-15 Earth Resources Function Demand Model for USA . . . 3-303.2-16 Navigation Function Demand Model for World Users . . 3-323.2-17 Aircraft Control Function Demand Model for World Users . 3-333.2-18 Communications and System Test Function Demand Model for USA 3-343.2-19 Astronomy Function Demand Model for USA . . . . 3-353.2-20 Tracking and Data Relay Function Demand Model for USA . 3-373.2-21 Solar Illumination Development Projection . . . 3-383.2-22 Space Power Relay Development Projection . . . . 3-403.3-1 World Population Trend ... . . . 3-423.3-2 World Illiteracy Trends . . . ... . 3-433.3-3 World Literate Population Trend . . . . ... 3-443.3-4 Demand Extrapolation Ratio Development . . . . 3-453.3-5 Extrapolation Ratios for Principal World Areas '. . . 3-473.3-6 World National Space Applications Program Extrapolation

Ratios . . . . . . . . . . 3-503.4-1 Intelsat Traffic Percentage for the Common

Intelsat/Domsat Functions . . . . . . 3-563.4-2 World Intelsat Forecast by Continental Area . . . 3-583.4-3 World Intelsat Forecast by Satellite Location . . . 3-593.4-4 Real Time Communications Demand Duty Cycle

for a Single Time Zone . . . . . . 3-603.4-5 World Domsat Forecast by Continental Area . . . 3-623.4-6 World Mersat Forecast . . . . . . 3-633.4-7 World Nacsat Forecast . . . . . . . 3-65

- ix -

SD 73-SA-0036-4

t*Space DivisionNorth American Rockwell

Figure [ Page

3.4-8 World ATS Forecast :. . . 3-663.4-9 World Astronomy Forecast 3-673.4-10 World TORS Forecast 3-683.4-11 A Lunetta System 3-703.4-12 Reflector Design and Positioning 3-713.4-13 Lunetta Uses and Size Requirements . ... . . 3-723.4-14 Typical Location of Lunetta Illumination Areas . . . 3-733.4-15 Power Relay Satellite . 3-743.4-16 Global Heat Sinks, Solar-Intense and High Energy--

Consumption Regions . . . . . . . . 3-763.4-17 Typical Geosynchronous Power Relay System . . . . 3-773.6-1 Preferred Satellite Locations 3-883.7-1 Intelsat Traffic Model—Atlantic Ocean . . . . 3-913.7-2 Intelsat Traffic Model-^Pacific Ocean . . . . 3-923.7-3 Intelsat Traffic Model — Indian Ocean . . . 3-933.7-4 Domsat Traffic Model—North and South America ... . 3-943.7-5 Domsat Traffic Model--Europe/Africa/USSR (West)' . . 3-953.7-6 Domsat Traffic Model-USSR (East)/Asia/Austrailia/Oceana . 3-963.7-7 Mersat Traffic Model 3-97.3.7-8 Nacsat Traffic Model . 3-983.7-9 ATS Traffic Model—United States 3-993.7-10 ATS Traffic Model—Foreign . . . . . . . 3-1003.7-11 Astronomy Traffic Model--United States and Foreign . . 3-1013.7-12 TORS Traffic Model—United States 3-1023.7-13 TORS Traffic Model—Foreign . . . . . . . 3-1033.8-1 New Traffic Model Population Distribution . . . . 3 - 1 1 54.1-1 Geosynchronous. Orbit Trends for Active Satellites . . 4-44.1-2 Typical Ground Trace Pattern for Adjacent Satellites

Launched on the Same Date . . . . . . . 4-64.1-3 Typical Ground Trace Patterns for Adjacent Satellites

Launched Six Years Apart . . . . . . . . 4-74.2-1 New Traffic Model Zonal Distribution 4-144.2-2 Zone 1 Satellite Distribution Chart . . . . . 4-154.2-3 Zone 2 Satellite Distribution Chart

(Repeats Figure 2.0-3) 4-164.2-4 Zone 3 & 4 Satellite Distribution Chart . . . . 4 - 1 74.2-5 Zone 5 Satellite Distribution (Zone 5 140°W - 45°W) . . 4-184.2-6 Zone 6 Satellite Distribution Chart 4-194.2-7 Recommended Alternate Solution . . . . . . 4-225.2-1 Nacsat Constellations 5-115.3-1 Region I - Data Relay Platform Locations . . . . 5-195.3-2 Region II - Data Relay Platform Locations . . . . 5-205.3-3 Region III - Data Relay Platform Locations. . . . 5-215.3-4 Region IV - Data Relay Platform Locations . . . . 5-225.3-5 Nacsat Data and Communications Links . . . . . 5-28

- x -SD 73-SA-0036-4


TABLES

Table

2.0-12.0-22.0-33.1-13.1-23.1-3

tl3.4-33.4-43.5-13.8-13.8-23.8-33.8-43.8-53.8-63.8-73.8-83.8-93.8-104.1-14.1-24.2-14.2-24.2-3

5.1-15.2-15.2-25.3-15 3-2

5.3-35.3-4

5.3-55.3-6

Traffic ModelModel (Through 1990).

New Traffic Model SummarySatellite Distribution for the NewPlatform Inventory for New TrafficCandidate Functional ApplicationsCandidate Communications and Data Functional ApplicationsCandidate Science and Applications FunctionsFunctions Allocated to Dedicated Satellite TypesIntelsat Communications FunctionsEstimated?,Percent of Intelsat Communications to Total .Percent of Total Functional Traffic That is InternationalFunctional Satellite Characteristics Criteria SummaryNew Traffic Model Summary . .New Traffic Model Summary - Active Satellites .New Traffic Model Summary - Inactive Satellites.New Traffic Model Summary - Satellites DeliveredNew Traffic Model Summary - Satellites RecoveredNew Traffic Model Summary - Active Satellites by Area .New Traffic Model Summary - Inactive Satellites by AreaNew Traffic Model Summary - Delivered Satellites by AreaNew Traffic Model Summary - Recovered Satellites by AreaNew Traffic Model Summary - Geographic DistributionSatellite Distribution for the New Traffic ModelActive Satellite Spacing for New Traffic Model (1990) .Navigation and Traffic Control System CharacteristicsZonal Satellite Distribution Spacings . . . . .Interference Levels Versus Zonal Spacings(980foot Ground Antennas)New Traffic Model Satellite CharacteristicsFunctional Grouping Considerations . . . . .Theoretical Minimum Functional Grouping Inventory .Common Support Module Functional Requirements . . .Geosynchronous Data Relay Satellites Distribution(New Traffic Model - 1990) . . . . . . . .Regional Characteristics . . . . . .Regional Data Relay Platform Requirements(New Traffic Model - Domsats - 1990)Observational Platform Requirements . . . . .Nacsat Platform Requirements . . . . . .

Page

2-32-42-83-33-43-63-513-533-533-553-803-1063-1073-1083-1093-1103-1113-1123-1133-1143-1164-94-104-124-20

4-215-75-95-10 '5-13

5-165-15

5-175-245-26

SD 73-SA-0036-4


ASCS

ATS

CCD

CCIR

CM

C/N

COMM

Comsat

CSM

DMS

Domsat

ECS

EIRP

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FM

GEOPAUSE

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IPACS

Mersat

Navsat

ABBREVIATIONS

Attitude stabilization and control system

Applications Technology Satellite

Charge coupled device

Consultative Committee for International Radio

Crew module

Carrier-to-noise ratio

Communications. •

Communications Satellite

Common support module

Data management subsystem

Domestic Communications Satellite

Environmental control subsystem

Effective isotropic radiated power

Electrical power subsystem

Frequency division multiplexing

Frequency modulation

Geodetic satellite in polar geosynchronous orbit

Geosynchronous solar electric propulsion stage

International Communication Satellite

Integrated power and attitude control system

Metrology and Earth Observations Satellite

Navigation and Traffic Control Satellite

- xin -SD 73-SA-0036-4


OTS Orbital transportation system

PCM Pulse code modulation

PSK Phase shift keying

RCS Reaction control subsystem

RSU Remote service unit

. SATA Small Application Technology Satellite

SEP Solar electric propulsion

SGLS Space-ground link subsystem (part of U.S. Air Force SatelliteControl Facility)

SNR Signal-to-noise ratio

SSM Spares storage module

STDN Spaceflight tracking and data network

StS Space transportation system

TDMA Time division multiple access

TORS Tracking and Data Relay Satellite

tPS Thermal protection subsystem

TT&C Tracking, telemetry and command

UHF Ultra high frequency

VHF Very high frequency

WARC World Administrative Radio Conference

XMTR Transmitter

- xiv -

SD 73-SA-003§4


1.0 INTRODUCTION

This volume presents the traffic analyses and system requirements datagenerated during the Geosynchronous Platform Definition Study. It is dividedinto two parts: the baseline traffic model and the new traffic model.

The new traffic model discussed in this part was derived principally fromforecasts of user demands and was intended to reveal the true potential forgeosynchronous traffic. Study results presented in this part include:

1. Selection of candidate functions employing geosynchronousoperations, development of forecast models projecting userdemand levels and growth profiles for each function, and thesynthesis of traffic elements and delivery schedules based onsatellite characteristics similar to those contained in thebaseline traffic model.

2. Satellite location criteria and the resulting distribution ,of the satellite population.

3. Geosynchronous orbit saturation analyses, including theeffects of satellite physical proximity and potential electro-magnetic interference.

4. Platform requirements, which differ from those generated bythe baseline traffic model because of the additional amountand types of traffic.

As with the baseline model, the development of the new traffic model isdescribed and its missions analyzed to determine the potential grouping ofsatellites for geosynchronous platforms. Satellite crowding also was inves-tigated based on the traffic indicated in the new model. These efforts werecombined with those resulting from the baseline traffic model study to pro- -vide the system-level requirements and guidelines for the candidate platformdesigns presented in Volume V. They also served as the key source for keymission and schedule data used in the program evaluation presented in VolumeVI.

1-1SD 73-SA-0036-4


,2.0 SUMMARY

This section provides a condensed summary of the traffic analyses andsystems requirements for the new traffic model. The results of each studyactivity are explained, key analyses are described, and important results arehighlighted.

NEW TRAFFIC MODEL

The new traffic model was structured on the basis of the utilitarianbenefits it provides to mankind. This represents a different approach thanapplied to the baseline traffic model described in Part 1. The baseline modelwas based principally on historical trends and provided a traceable base ofmission planning data which relates to other industry studies. The new trafficmodel reflects the dynamic growth in satellite communications and other spaceapplications which is just beginning to emerge. It was intended to representthe true potential for geosynchronous traffic through 1990. These trafficmodels form the basis for defining the nature, number, and schedule of geo-synchronous mission activities which are utilized as key input data to manyimportant tasks. ,

The approach to construction of the new traffic model is outlined inFigure 2.0-1. Twenty-two major functions were identified which require theunique features provided by geosynchronous operations. Forecast models ofuser demands and their projected growth profiles were constructed for eachfunction. Commercial functions .were based on estimates of the user populationfor the United States and then extrapolated to other world areas. Scientificand developmental functions were based on budget forecasts of U.S. and foreignnational space programs. These provided the requirements for synthesizinggeosynchronous programs. For convenient comparison with the baseline trafficmodel, the functional demand profiles were converted into the number ofequivalent satellites required to satisfy the demands. The resulting trafficsummary for the new model is shown in Table 2.0-1. As can be seen, 413 satel-lites are required compared to the 180 contained in the baseline model.

The same satellite location criteria used to determine satellite distri-bution for the baseline traffic model were applied to the satellite populationin the new model. The resulting distribution by year for each of the sixzones is shown in Table 2.0-2. Also included are the number of inactive satel-lites remaining on-orbit if all those whose active mission life expires afterthe reusable tug becomes available (1982) are retrieved. If no satellitesare retrieved and allowances are made for the pre-1973 population and projectedestimates of DoD traffic, the total 1990 on-orbit population will become 499satellites. .

2-1SD 73-SA-0036-4

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SD 73-5^-0036-4^

ft*Space DivisionNorth American Rockwell

GEOSYNCHRONOUS ORBIT SATURATION

The orbit saturation analysis for the new traffic model was the same asfor the baseline model: to determine the nature and degree of satellite con-gestion in geosynchronous orbit if the current process of launching individualsatellites is continued through 1990.

As with the baseline model, satellite physical proximity and potentialelectromagnetic interference (EMI) were investigated for the active satellitepopulation. The larger number of satellites in the new model forced a closerlook at the simplified one-dimensional spacing model developed for the base-line traffic analyses. In this case, the effects of luni-solar perturbationswere applied to the orbits of the active satellites. Even though the normaleast-west stationkeeping operations are employed, the luni-solar perturbationscause long-period (53 years) cyclic changes in the inertia! orientation ofgeosynchronous orbits.

These changes and their effects on the satellite ground traces are depictedin Figure 2.0-2. Geostationary satellites Si and $2, launched in differentyears, acquire different orbit inclinations (il and 12), and their orbit nodesare separated by ari: angle dependent upon the interval between their launches.Their resultant ground trace patterns reflect these differences through thesize of their figure eight patterns and the relative phase relationshipswithin their figure eight patterns. The maximum phase mismatch which can occurwithin the seven-year active satellite lifetimes contained in the traffic modelis slightly greater than one-tenth of a day. The effect of this mismatch isnegligible on their separation distance at the point of closest approach.Thus, the minimum spacing limit between adjacent satellites is governed , ,principally by their east-west stationkeeping capability. For this analysis,,a 50 percent margin was applied to a typical stationkeeping band of +0.125degree to produce an allowable spacing limit of 0.40 degree.

This compares favorably with the actual spacing projected for the activesatellite populations in the new traffic model which range from 0.4 to 1.2degrees. It was concluded that satellite physical proximity was not a criticalproblem with the 239 active satellites in the new mode-. Even extending thisnumber to include inactive and estimated DoD satellites (499 satellitesassuming no retrieval), the problem is not expected to be critical. As notedin Part 1, the combined effects of all orbit perturbations carry the inactivesatellite populations through a total "swept" volume of space of nearly 3 x1010 n mi3. The average volume for a total satellite population of 499 be-comes approximately 60 million n mi3 per satellite. This enormous volumeprecludes any real collision hazards and supports the conclusion that physicalcrowding will not pose a critical problem.

Although there is no likely collision hazard, 1f all the communicationsrelay satellites are configured similar to the currently planned Intelsat/Domsat satellites (24-transponder, C-band units), as assumed for purposes ofconstructing the satellite populations in the new traffic model, it is virtuallycertain that severe EMI problems will result. Even removing the conservatismin the EMI spacing model constructed for the baseline traffic analyses wouldnot eliminate the problem. Utilizing 97-foot instead of 60-foot ground

2-5SD 73-SA-0036-4


RELATIVE PHASE -I

RELATIVE--^NODE x

s, \.GROUND TRACES

MINIMUMSPACING

Figure 2.0-2. Satellite Spacing Geometry

antennas and allowing for separation distance effects in the ground stationlocations could perhaps reduce the spacing requirement from 4.6 degrees betweenadjacent C-band satellites to a value approaching 3.0 degrees. This spacingcriterion is violated in all six zones, with a peak density approaching 0.8degree per satellite, as shown in Figure 2.0-3 for Zone 2. Hence, it isconcluded that some form of multi-function platform utilizing additional fre-quency bands (K-band) will be required.

GEOSYNCHRONOUS REQUIREMENTS ASSESSMENT

Geosynchronous requirements assessment involves translating the trafficanalysis, satellite/payload definitions, and mission characteristics datainto system-level requirements for geosynchronous platforms. It includes thegroupability of payloads through physical and functional considerations andthe influences of various modes of on-orbit servicing and their relatedcriteria factors. These requirements form the basis for the subsystem sizing,mission and subsystem equipment packaging, configurational arrangement, and'related design analyses leading to the platform conceptual designs presentedin Volume V.

f\To determine the general features and size of geosynchronous platforms,

the important satellite/payload characteristics and related mission functionswere assessed for compatibility and commonality. Since the same categories offunctions appear in both the baseline and the new traffic model and theirgeneral operational features are similar, the grouping analysis results for

2-6S.D 73-SA-0,Q36-4

Space uivisionNorth American Rockwell

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the baseline traffic are generally applicable to the new traffic model. Thefour global regions defined for the baseline traffic (Figure 2.0-5, Part 1)are applicable and the solar outage considerations require similar separationof communications payloads within each region. The other grouping constraints,such as unique placement, incompatible pointing envelopes, configuration/designcomplexities, and "uneven" mixes of payloads (oversize, standard, etc.) withineach region,also apply and result in a similar inventory of platform types.

However, several important differences do appear. The amount-of communi-cations traffic, both domestic and international, is nearly quadrupled in thenew traffic model. This means communications payloads in each region must befurther separated because of technology limits. Sufficient bandwidth is notavailable within the usable spectrum to provide non-interfering communicationsat the traffic levels specified in the model. Frequency reuse utilizingmultiple platforms is required. All platforms would operate with the samefrequency bands but would be physically separated to preclude EMI. Thus,each communications relay platform satisfying the new traffic model would bea high-capacity device utilizing as much of the EM spectrum as technology per-mi ts.

In addition to differences in communications traffic, the navigation andtraffic control function exhibits several new features in the new trafficmodel. Traffic coverage was extended to the polar regions, which requiresinclined elliptical orbits, and the concept was extended to include position/navigation update signals in addition to the basic flow of traffic planningand control information. The orbit incompatibility coupled with the high powerdemands for transmitting traffic control information and navigation signals tothe low-performance mobile receiver installations on the individual user vehicles

2-7

SD 73-SA-0036-4

Space Divisio iNorth American Rockwell

precluded their grouping with other geosynchronous payloads. Thus, thenavigation and traffic control payloads were separated from the communicationsrelay functions in the new traffic model.

Other functions remain relatively unchanged, although additional numbersof payloads may be present because of the introduction and buildup of foreignspace programs. The complete inventory of platform types is summarized inTable 2.0-3 for the new traffic model. Again, as with the baseline traffic,the subsystem support requirements fall into the same general size range forall the platforms in this inventory. Also, the servicing requirements aresimilar. The same configurational arrangements for equipment access andprovisions for servicing apply to platforms for both traffic models. Thus,the key differences between the baseline and new traffic models are centeredin the communications relay traffic, its amount and distribution, and thenavigation and traffic control functional and operational characteristics.These new requirements are the focal point for the platform configuration anddesign analyses for the new traffic model presented in Volume V.

Table 2.0-3. Platform Inventory for New Traffic Model(Through 1990)

Platform Type

Data relayTORS*

i.

Earth observationsAstro-physicsNavigation and traffic

control

REGIONI

4

4

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2

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4

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III

7

2

1

2

1 + (4)

IV

43

1

41 + (4)

* Regional assignments are approximate because of unique placementrequirements

** Platforms in parenthesis occupy inclined elliptical orbits

2-8SD 73-SA-0036-4


3.0 NEW TRAFFIC MODEL

The new geosynchronous traffic model was developed to accomplish anumber of major objectives of the Geosynchronous Platform Definition Study.It was derived specifically from programs that maximize the benefits tomankind of geosynchronous space utilization.

The purpose of the new traffic model was to provide an independent basis(from current mission definitions) for subsequent analyses of geosynchronousmission characteristics, orbit saturation, requirements assessment', platformconceptual designs, and geosynchronous program analysis. Similar analyseswere performed using the baseline traffic model. The relationship of thenew traffic model to each of these analyses is shown in Figure 3.0-1.

The developmeht approach for the new traffic model included: (1) the :definition of beneficial geosynchronous mission objectives; (2) the projec-tion of these objectives into mission requirements for the U.S. users and theextention of this to the world users; (3) the identification of the number ofprogram elements (functional satellite types) needed to satisfy the definedrequirements; (4) the definition of the program element characteristics; and(5) finally, the determination of the traffic schedule for each functionalsatellite type including geographic location.

The analyses performed in completing the definition of the new geo-synchronous traffic model were based on preliminary Rockwell studies ofinformation transfer traffic and utilitarian applications functions. Theanalyses performed in this study extended the earlier work to provide betterdefinitions of functional and world user requirements in addition to thedevelopment of the new traffic model.

3-1SD 73-SA-0036-4

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3-2SD 73-SA-0036-4


3.1 CANDIDATE USER ORIENTED FUNCTIONAL APPLICATIONS

Candidate functions applicable to geosynchronous satellite systems arelisted in Table 3.1-1 under three major categories. Communications and datafunctions are those which are applicable to international and domestic commu-nications satellites. Science and applications functions are those specialservices that: (1) utilize sensors or equipments (onboard or remote) forglobal earth and environmental observations or for ship and air vehiculartraffic control; (2) include space observations, the development and test ofgeosynchronous satellite systems of all kinds, and communications and datarelay of low altitude science and applications satellite information; (3)relay light and power for terrestrial uses. National Defense includes thoseglobal communications and sensor functions necessary for national security.A detailed identification of these functions as well as communications andsensor function data traffic is classified information and is not includedin the subsequent analyses and traffic model development.

Table 3.1-1. Candidate Functional Applications

Communications and Data

1.2.3.4.5.6.7.8.9.10.11.12.13.14.

EducationCommercial broadcastTeleconferenceTelegraphPost officeMedical data bankBanking/business/credit trans.NewspaperElectronic publishingCivil defenseWelfare data banksLibrary data banksPrivate record banksTelecomputations

Science and Applications

1.2.3.4.5.6.7.8.9.

National Defense - communications and

MeteorologyEarth resourcesNavigationAircraft controlCommunications and systems testAstronomyTracking and data relaySolar illuminationSpace power relay

sensor data

COMMUNICATIONS AND DATA

The subfunctions or scope of the 14 general functions listed in Table3.1-1 are presented in Table 3.1-2. A general identification of source anduser is also included. The function scope is identified to provide the basisfor quantifying the amount of communications and data traffic that is projectedfor satellite relay. Most of the communications and data functions involve

3-3

SD 73-SA-0036-4

Space Division,North American Rockwell

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two-way transmissions; i.e., send and receive at both ends of the transmissionlink. Exceptions would include commercial broadcast, most education, news-paper, and electronic publishing.^ Although some functions may be performedin several specific centralized locations, the functional users are locatedin all geographical land areas and more sparsely distributed in some oceanareas. Therefore, communications in this category may be point to point(telephone call), point to points (commercial broadcast), and points to pointto points (data bank, etc.).

SCIENCE AND APPLICATIONS

The scope of science and applications functions is shown on Table 3.1-3.Most of the science and applications functions, with the exception of astronomy,solar illumination, and space power relay receive information from almost allof the global surface and/or low altitude space. Satellite relay or trans-mission of science and applications data will be directed to one or severalspecific functional centers for processing and distribution to users. Inseveral cases data distribution or response to the users will be accomplishedby satellite as is the case for navigation, air traffic control, tracking andsatellite data control. The science and applications functions will, there-fore, require points to point (meteorology, etc.), points to point to points(navigation and traffic control, etc.), and point to point (power relay,astronomy, and illumination). . -

3-5SD 73-SA-0036-4

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3-6SD73-SA-0036-4


3.2 U.S. DATA TRAFFIC FORECASTS(COMMUNICATIONS, SCIENCE AND APPLICATIONS)

Communication and data traffic forecasts have been developed for each ofthe candidate functions listed in Tables 3.1-2 and 3.1-3 based on projected U.S.user demands. A primary reference source utilized for 12 of the 14 communica-tions and data functions was "A Study of Trends in the Demand for InformationTransfer", which was completed by the Stanford Research Institute (SRI) inFebruary 1970 (Reference 3-1). Rockwell has developed the user demands forthe remaining two communications and data functions (welfare data bank andtelecomputations) and each of the science and applications functions. It isnoted that the SRI data source presents the information traffic demands interms of "total traffic" and "long distance traffic" only. Rockwell hasextended these data further in that the percentage of the long distance trafficthat would feasibly be carried by geosynchronous satellite relay has beenforecasted.

This forecast analysis was accomplished by comparing measured U.S. 1970Intelsat communications and data traffic rates with measured long distancecommunications and data traffic rates for the teleconference and commercialbroadcast functions. (These two functions made'up more than 95 percent of allIntelsat and long distance traffic.) The data comparison showed that 1.6 per-cent of the long distance communications traffic was being transferred bysatellite. To determine the expected growth rate of satellite'communicationstraffic, Comsat, Western Union, and.several other domestic satellite contractorforecast estimates were obtained. These showed forecasted satellite usagegrowth rates of 30 to 40 percent per year for the next 5 to 10 years. Theserates were based on previous historical growth trends. A projected growthrate of 25 percent per year was used from 1 970 to the year 2000; the loweraverage rate being used because of the longer period (30 years) of the fore-cast. Using this projection, the long distance teleconferencing and commercialbroadcast traffic carried by satellite will be about 30 percent of the totallong distance traffic forecasted in the year 2000. Since ground versussatellite data links will probably remain highly cost competitive (at least inthe U.S.) in the future, it is envisioned that an upper limit of 50 percent oflong distance traffic will be carried by satellite in the year 2030. Figure3.2-1 shows the present and projected ratio of satellite to long distancecommunications and data traffic based on the projected growth points.

Although Figure 3.2-1 is based on projections of the teleconference andcommercial broadcast functions (which are expected to represent more than 90percent of all communications and data traffic in the future), the ratio his-tory projected should also be valid for the other communications and datatransfer functions. Each of the functions in this category use the samecommunications frequencies, and the only factors that inhibit their presentimplementation using satellite relay are applicable user software programs,ground terminals and distribution networks. Therefore, the data shown inFigure 3.2-1 are used to forecast the satellite traffic based on total longdistance traffic projections.

3-7

SD 73-SA-0036-4

r* •*£- p-C.- ^M.1* .'•Space DivisionNorth American Rockwell

1970 1980 1990 2000 2010 2020 2030T tAK

Figure 3.2-1. Ratio of Satellite to Long Distance Information Traffic

Frequent reference has been made to long distance information traffic.This, raises the question, how far is "long distance"? SRI research of tele-phone, mail, and credit transaction functions produced several distance valuesfor long distance traffic. Based on their values, a distance greater thanTOO miles is used to distinguish long distance traffic from local traffic.Another approach to the definition of "long distance" resulted from recentRockwell cost comparisons of satellite traffic to ground traffic. These marketstudies showed that satellite transmission costs are cheaper than terrestrialmicrowave links for distances greater than 300 miles and cheaper than telephonelines for distances greater than 150 miles. This reinforces the interpretationfrom SRI analyses, that any traffic greater than 100 miles can be cate-gorized as long distance. The Rockwell cost comparisons also reinforce theconcept that satellite information traffic may one day approach the 50 percentlevel of all long distance traffic.

3-8

SD 73-SA-0036-4


The following paragraphs under each function contain reference datasources, approach, a sample computation used to determine the functional demandforecast, and the extrapolation basis or rationale.

EDUCATION

The functional information demand for education was extracted from theSRI function, television transmission (Reference 3-1). In 1970, there wasone educational network and three commercial networks. SRI projects 20 net-works (both education and commercial) in 1990 broadcasting 72,000 hours peryear. Based on a 9-hour day and 5 day-week for educational TV and 15 hour-dayand 7 day-week for commercial TV, this equates to 12 educational networks and8 commercial networks in 1990. Twelve educational networks or, more probably,12 educational channels in 1990 is not considered excessive when internationalor intranational low cost communications are a reality. Several of thesechannels may be foreign language oriented for outgoing and incoming educationalprograms.

For 1990, the average total long distance data rate projected is:

(12 channels) x (64 x 106 bits/second) = 7.68 x 108 bits/second

for a nine-hour day. The growth trend for the education function data ratesshown in Figure 3.2-2 is based on: one channel, 8 hours per day in 1970;8 channels, 8 hours per day in 1980; 12 channelS; 9 hours per day in 1990; and14 channels, 10 hours per day in 2000. The long distance and satellite trafficdata rates are both illustrated in Figure 3.2-2.

COMMERCIAL BROADCAST

The information demand projection for commercial broadcast (by television)was obtained from Reference 3-1. As described previously, this functional datarate was computed with the education function. Based on the SRI 1990 projec-tion and subtracting the education function, eight commercial channels, eachbroadcasting 5460 hours per year, are forecasted for 1990.

The average total long distance data rate projected for 1990 is:

(8 channels) x (64 x 106 bits/second) = 5.12 x 108 bits/second

for a 15-hour day. The growth trend for the commercial broadcast functiondata rates shown in Figure 3.2-3 is based on: 3 channels, 11 hours per dayin 1970; 6 channels, 12 hours per day in 1980; 8 channels, 15 hours per day in1990; and 9 channels, 16 hours per day in 2000. Both long distance andsatellite data rates are illustrated for commercial broadcast in Figure 3.2-3.

3-9SD 73-SA-0036-4


10I960

YEAR1990 2000

Figure 3.2-2. Education Function Demand Modelfor USA

3-10SD 73-SA-0036-4


101970 2000

Figure 3.2-3. Commercial Broadcast Function Demand Model

for USA

3-11

SD 73-SA-0036-4


TELECONFERENCING

Teleconferencing includes both telephone and videophone. Long distanceteleconferencing frequencies have increased more than eight percent per yearin the last few years. As more and more videophones are added to homes inthe next 10 to 15 years, teleconferencing data rates will increase at evengreater rates. Reference 3rl forecasts 48 billion long distance telephonecalls and 100 million long distance videophone calls made in 1990. Thesevalues do not seem unreasonable in view of continual lowering of satellitecommunications channel lease costs. Current cost trends show that a voicechannel price rate may be as low as $200 to $300 per year in the late 1970'susing Intelsat V. Even if videophone requires up to 1000 voice channels, a3-minute call by satellite may cost only two dollars.

The long distance data rate forecasted for 1990 based on the abovenumber of calls is:

(48 x 109 calls/year) x (6 minutes/call) x (60 seconds/minute)x (64,000 bits/second) •=- (3.15 x 107 seconds/year) = 3.51 x 1010

bits/second for telephone, and

(100 x 106 calls/year) x (6 minutes/call) x (60 seconds/minute)x (6.3 x 106 bits/second) -=- (3.15 x 107 seconds/year) = 7.2 x 109

bits/second for videophone ' •' ".

Videophone data rates per year are expected to increase more than telephonedata rates so that by the year 2000 the long distance videophone data ratewill be 1.8 x loll bits/second compared to the long distance telephone datarate of 8.0 x 10^° bits/second. Figure 3.2-4 shows the data rates projectedfor long distance and satellite traffic. In 1970, teleconferencing made upabout 95 percent of all satellite communications traffic. Likewise, in theyear 2000 it is expected to remain at about 95 percent of all communicationstraffic.

TELEGRAPH

Long distance telegraph traffic has steadily declined since 1945. It isprobable that personal greetings and business telegrams may continue to declinebecause of increased business data facsimile traffic (using telephone lines)and lowered telephone night rates which are increasing personal greetings bytelephone.

The SRI forecast of telegraph traffic for 1990 (Reference 3-1) is basedon the following:

(35 x 106 messages/year) x (20 words/message) x (50 bits/word)T (3.15 x 107 seconds/year) = 1 . 1 1 x 103 bits/second

3-12

SD 73-SA-0036-4


o i jL... LONG DISTANCE

t"«

I

1»70 I960 YEAH1990 2000

Figure 3.2-4. Teleconference Function Demand Modelfor USA

3-13

SD 73-SA-0036-4


Since the forecasted continuous data rate shown is so small, this function isassumed to be included in the teleconferencing function.

POST OFFICE

The total of long distance first class and airmail letters has shown aconsistent growth rate of 4.5 percent per year. These data are obtained fromthe "Annual Report of the Postmaster General" for GFY 1971. The SRI report(Reference 3-1) showed similar growth projections and estimated the number offirst class letters that would be suitable for transmission by satellite.Present new postal services include mailgrams (sent by teleprinters - aWestern Union function) and facsimile mail (to be extended soon to 100 majorcites). Facsimile mail using ground communication links is the forerunnerof the anticipated satellite mail system. These innovations may result ingreater growth rates than forecasted.

The long distance postal data rate forecasted for 1990 is based on thefollowing:

(21.85 x 109 pieces mail/year) x (300,000 bits/piece)* (3.15 x 107 seconds/year) = 2.08 x 108 bits/second

Figure 3.2-5 illustrates the postal function long distance and satellite fore-casted data rates. It is not expected that satellite transmission of mailwill occur until 1975 to 1980 since initiation of this function will bedependent on the U.S. Domsat system.

MEDICAL DATA BANK

Precursor experiments and tests of transmitting medical data such aselectrocardiograms and medical diagnoses are being conducted using theApplications Technology Satellites. Reference 3-1 provides the basis forprojecting present and future medical data bank data rates. Remote medicaldiagnosis, literature searches, and electrocardiogram and other diagnosticdata analysis are included.

The long distance data rates forecasted in Figure 3.2-6 for 1990 arebased on the following:

(180 x 106 cases/year) x (30,000 bits/case) * (3.15 x 107 seconds/year) =1.71 x 10$ bits/second for remote diagnosis, plus

(180 x 106 searches/year) x (30 pages/search) x (3 x 104 bits/page)•* (3.15 x 107 seconds/year) = 5.14 x 106 bits/second forliterature searches, plus

(80 x 106 tests/year) x (30,000 bits/test) T (3.15 x 107 seconds/year) = 7.61 x 10^ bits/second for diagnostic test analysis,for a total of 5.39 x 106 bits/second.

3-14SD 73-SA-0036-4


10*

H i t LONG DISTANCE

5'-

1, SATELLITE

It

1fe

ill

niHI

*• '1iilL 1 1

1970 I960YEAH

1990 2000

Figure 3.2-5. Postal Function Demand Modelfor USA

3-15

SD 73-SA-0036-4

•v Space DivisionNorth American Rockwell

LONG DISTANCE

i :4

SATELLITE

S'-

1.-IQ

l!i!M

M

w mm

II

Iin

»Jili1970 I960

YEAR 1990 2000

Figure 3.2-6. Medical Data Bank Function Demand Model

for USA

3-16

SD 73-SA-0036-4


The 12 percent per year long distance growth rate seems justified as commu-nications costs are lowered and general practitioners do more long distanceconsulting with specialists (as well as specialist-to-specialist consultations).

BANKING, BUSINESS, AND CREDIT TRANSACTIONS

The following services are forecasted in Reference 3-1 which are repre-sentative of this function: patent searches; checks and credit transactions;stock exchange quotes; stock transfers; airline, auto, hotel, and entertain-ment reservations; and national legal information.

The 1990 long distance traffic model is based on the following:

(8.1 x 106 searches/year) x (6 pages/search) x (3 x 106 bits/page)* (3.15 x 107 seconds/year) = 4.63 x 106 bits/second for patentsearches; plus

(136 x 109 transactions/year) x (50 characters/transaction)x (8 bits/character) •* (3.15 x 10? seconds/year) =1.73 x 10° bits/second for checks and credit transactions; plus

(4 x 109 transactions/year) x (100 bits/transaction)T (3.15 x 107 seconds/year) = 1.27 x 104 bits/second forstock exchange quotes; plus

(4.9 x 109 transactions/year) x (3000 bits/transaction) -•5- (3.15 x 107 seconds/year) = 4.67 x 105 bits/second forstock transfers; plus

(1.4 x 109 passengers/year) x (3 transactions/passenger)x (200 characters/transaction) x (8 bits/character)T (3.15 x 107 seconds/year) = 2.13 x 105 bits/second forairline reservations; plus

(14 x 107 reservations/year) x (1000 bits/reservation)* (3.15 x 107 seconds/year) = 4.44 x 103 bits/second forauto and hotel reservations; plus

(2.0 x 10^ reservations/year) x (200 bits/reservation)T (3.15 x 107 seconds/year) = 1.27 x 103 bits/second forentertainment reservations; plus

(3.0 x 107 searches/year) x (10 pages/search) x (3 x 104 bits/page)T (3.15 x 107 seconds/year) = 2.86 x 105 bits/second for national,legal information,for a total of 7.34 x 106 bits/second.

3-17 SD 73-SA-0036-4

Figure 3.2-7 presents the total of all these services. The long distancetraffic growth rate averages 3.8 percent per year from 1970 to 2000.

Bil'

i0 «-

5-

s,.<?

ui

S--

1,to!

10"

Hi;

.ft

SATELLITE

1970 1980YEAR

1990 2000

Figure 3.2-7. Banking, Business, and Credit Transaction Function Demand Modelfor USA

3-18

SD 73-SA-0036-4


NEWSPAPER

Long distance facsimile transmittal of 20 different newspapers is fore-casted for the year 1990 by SRI (Reference 3-1). This growth is projectedfrom two newspapers currently using this service. Expansion should be rapidwith the advent of low cost data transmission by Domsat.

The:long distance data rate for 1990 is based on the followingassumptions:

(20 newspapers using service) x (365 days/year) x (50 pages/day)x (180 x 106 bits/page) * (3.15 x 107 seconds/year) =2.09 x 10

6 bits/second

Figure 3.2-8 presents the long distance and satellite traffic trends for thenewspaper function. The data rate shown is a continuous average rate.Actual data transmission by each paper might be at considerably higher datarates over shorter time intervals.

ELECTRONIC PUBLISHING '""'-.'

This function envisions the remote publication of popular books andbest seller weekly and monthly magazines. The implementation of this function,as with many others, depends on the cost savings that can occur using thispublication and distribution method. Reference 3-1 provides forecast valuesto 1990. ;

The long distance demand model for 1990 is based on the followingcomputation:

(105,000 issues/year) x (107 bits/issue) * (3.15 x 107 seconds/year) = 3.33 x 104 bits/second

Since the forecasted average data rate of this function is so small, itis assumed that this service is included with the newspaper function.

CIVIL DEFENSE

The major subfunctions of civil defense relate to police and publicservices in addition to periodic tests and regional area use of disasterwarning communication networks. The specific services quantified are:national crime information; stolen property information; facsimile transmissionof mug shots, fingerprints, all-points bulletins, court records, and,vehicle and personal license registration. Again, Reference 3-1 providesthe basis for this forecast.

3-19

SD 73-SA-0036-4


¥••

Ili •L , s

*H+

1

E L144 I

LONG DISTANCE

o

f§ SATELLITE

7

i

1970 1980 YEAR 1990 2000

Figure 3.2-8. Newspaper Function Demand Model

for USA

3-20

SD 73-SA-0036-4


The 1990 long distance forecast is based on the following computations:

(7 x 10? transactions/year) x (3 x 105 bits/transaction)

* (3.15 x 107 seconds/year) = 6.67 x 105 bits/second fornational crime information; plus

(1.16 x 106 cases/year) x (3000 bits/case) -=- (3.15 x 107 seconds/year)= 110 bits/second for stolen property information; plus

(1.25 x 107 cases/year) x (10 pages/case) x (3 x 106 bits/page)* (3.15) x 107 seconds/year) = 1.19 x 107 bits/second for mugshots, fingerprints, etc.; plus

(3.02 x 108 registrations/year) x (6000 bits/registration)T (3.15 x 107seconds/year) = 57,600 bits/second forvehicle registrations and drivers licenses*for a total of 1.26 x 107 bits per second.

Figure 3.2-9 shows the long distance and satellite forecasted data rates for1970 to 2000. The average long distance growth rate is about 7 percent peryear based on the increased rates of crime during the 1950 to 1970 time;period.

WELFARE DATA BANK

The principal services used to forecast welfare data bank data ratesinclude bookkeeping, employment services and payment records for all personsreceiving old age benefits, unemployment benefits, and medicare benefits.The forecasts are based on Rockwell analyses of data contained in the 1972World Almanac (Reference 3-2). Due to the rapid changes, both up arid down,in the number of benefit receivers in the past years (for which there arerecords), this model has been conservatively forecasted at a long termgrowth rate of about 1.5 percent/year which slightly exceeds the U.S. popula-tion growth history.

The 1971 long distance data rates for the above services are based onthe following computations:

(2.19 x 107 persons/year) x (13 transactions/person)x (200 characters/transaction) x (8 bits/character)7(3.15 x 10 seconds/year) = 1.45 x 10^ bits/second forold age benefits; plus

3-21

SD 73-SA-0036-4


LONG DISTANCE

-.*.

z

SATELLITE

$m

ft^

1980 1990 2000

Figure 3.2-9. Civil Defense Function Demand Modelfor USA

3-22

SD 73-SA-0036-4


(6.1 x 10 persons/year) x (30,000 bits/person) -r (3.15 x 107

seconds/year) = 5810 bits/second for Medicare records; plus

(8.34 x 106 persons/year) x (52 records/person) x (10,000 bits/

record) + (160,000 bits/initial record) v (3.15 x 10 seconds/year)

- 1.38 x 10 bits/second for unemployment services and records,,for a total of 1.58 x 10 bits per second.

Figure 3.2-10 illustrates the data rate traffic forecasted for 1971 to 2000.

LIBRARY DATA BANK

The library data bank is envisioned as a Library of Congress function ofthe future. This center could provide to remote users such services asremote title and abstract searches, remote library browsing searches, andinterlibrary transmittals of out-of-print books and documents (by facsimileor other means). Reference 3-1 provides the estimates of data rate trafficfor this function. •

The long distance data rate for 1990 is based on the following .computations:

(10 searches/year) x (30 pages/search) x (3 x 10 bits/page)

T (3.15 x 107 seconds/year) = 2.86 x 105 bits/second for title

and abstract searches; plus

(1.8 x 10 accesses/year) x (200 pages/access) x (3 x 10 bits/page)v (3.15 x 10 seconds/year = 3.43 x 10 bits/second for remotebrowsing; plus

(107 x books/year) x 10 bits/book) •*• (3.15 x'107 seconds/year)=3.17 x 10 bits/second for interlibrary transmittals,for a total of 3.78 x 107 bits/second.

Figure 3.2-11 shows the data rate forecasts from 1975 to 2000. Because ofthe expected usefulness of this service, long distance growth rates areinitially (1975 to 1978) predicted to be about 30 percent per year decliningto about 12 percent per year in 2000.

PRIVATE RECORD BANKS

Large companies, corporations, and large government agencies haveestablished corporate record data banks for their personal and business needs.This function assumes the eventual use of satellite transmittal for much ofthese data. The SRI report (Reference 3-1) provides the initial estimatesfor this function which is assumed to be representative for the year 1975.

3-23SD 73-SA-0036-4


1970 1980YEAR

1990 2000

Figure 3.2-10. Welfare Data Bank Function Demand Model; for USA

3-24

SD 73-SA-0036-4

LONG DISTANCE

/

§•-§::£>-2<= 4_IU

<

SATELLITE

4 •;

Wiliit HIlltt

1970 1980YEAR 1990 2000

Figure 3.2-11. Library Data Bank Function Demand Model

for USA

3-25

SD 73-SA-0036-4


The lon.g distance traffic data rate is based on the following values:

(400 large corporations or other) x (3 data transmission systems/corporations) x (25,000 messages/day) x (200 characters/message)x (10 bits/character) * (86,400 seconds/day) = 6.95 x 105

bits/second

It is estimated that this function will expand at the ra-te of 30 percent peryear between 1975 and 1980, 20 percent per year between 1980 and 1990, and6 percent per year from 1990 to 2000. Such systems as these are anticipatedto become economically feasible with the operational implementation ofDomsat. The expected satellite and long distance traffic for this functionis shown in Figure 3.2-12.

TELECOMPUT.ATI.ONS r

Telecomputations is the functional classification that covers computerdata transmission services for the small business organizations that cannotafford their own private computer. These businesses can effectively utilizea large centrally located computer(s) on a time sharing basis with accessthrough remote terminals. This function is also envisioned to become costeffective to remote households with the use of the telephone or satellite fordata transmittal from and to the remote terminal (in the home).

The following approach was used to develop the data rate forecasts forthis function. A cursory survey of the Los Angeles and Orange County tele-phone yellow pages showed the existence of several hundred computer datacenters of which approximately 35 can be addressed by remote services. Thelarge number of these centers verified the service demand by small businesses.Data from Reference 3-2 showed receipts and profit totals for U.S. proprietor-ships, partnerships, and corporations. Other statistical references indicatedthat operating costs averaged 65 percent of receipts and that about 5 percentof the operating costs were related to data processing. The cost for dataprocessing was assumed to be $400 per hour.

In time, every household may use a remote terminal (just as TV is now in95 percent of all homes) for large computer access (for scientific computa-tions or household records). It is estimated that these homes may averageone hour machine time per year. Using these assumptions and the availablestatistics from Reference 3-2, the total data rate demand for 1968 was 5.09 x109 bits/second. This value was given a constant annual growth rate of 6.5percent per year (1.5 percent user growth + 5 percent for increased services).Long distance traffic was assumed to vary linearly from 6 percent in 1968 to12.5 percent in 2000 of the total traffic rates computed. Potential satellitetraffic was estimated using values from Figure.3.2-1.

Figure 3.2-13 shows the results of this cursory analysis. The practicalityand wide use of this function via satellite transmission may be dependentupon nearby ground station terminals with access to Domsat-to-computer linksas well as lower computer costs and low remote terminal rental costs.

3-26SD 73-SA-0036-4


1970 1980 YEAR 1990 2000

Figure 3.2-12. Private Record Bank Function Demand Model

for USA

3-27SD 73-SA-OU36-4

DISTANCE

~J>0 .

I''<? 4-

SATELLITE

M titmt

M

<fll 111 ill Hi rti Ml Ik ill ill1970 I960 YEAI

1990 2000

; Figure.3.2rl3. Telecomputation Function Demand Model

for USA

3-28

SD 73-SA-0036-4


METEOROLOGY

A typical mid-1970 meteorological satellite will sense a number ofatmospheric conditions as well as relay data from numerous remote earthlocations. These locations are strategically distributed in both hemispheresto .provide weather data for all nations. The U.S. geographical area includingsome ocean areas to the east and west can be monitored by a single meteoro-logical satellite providing a zone of coverage for a .substantial portion ofthe western hemisphere. This zone would cover a minor circle on the earthranging from 76 degrees north to 76 degrees south and•+_ 76 degrees oflongitude from the satellite's location. This area is larger than requiredfor local U.S. weather observations and forecast needs. However, to satisfyU.S. international air traffic and maritime forecast needs, other zonal datafurther to the east and west of the U.S. are also required. For the modelshown, it is assumed that this other required zonal data compensates for thesouthern hemisphere zonal data at U.S. longitudes that is of little use tothe U.S. Therefore, the U.S. user requirements will be equivalent to thedata provided from a single zone. ;

Data from a single zone are initially expected to be equivalent to 107bits per second. As greater and more detailed area coverage is desired, thesingle zone data are expected to double in eight years, triple in 16 years,and quadruple in 24 years. This is equivalent to a periodic average growthrate of 9 percent per year in the first eight years, 5 percent per year inthe second eight years, and 3.65 percent per year in the third eight-yearperiod. This projected forecast is illustrated in Figure 3.2-14.

EARTH RESOURCES

The mid-1970 geosynchronous earth resources satellite will also senseand continuously7transmit data from scanned areas at an initial rate ofapproximately 10 bits per second. This system will be an outgrowth of thepresent Earth Resources Technology Satellite (ERTS) and will provide datafor: mineral and land resource analysis; agriculture, forestry, and rangeresource analysis; water and marine resource analysis; soil differentiationand topographic information. As more sensitive sensors are developed foruse at geosynchronous altitude and more detailed and greater land areacoverage is desired, the data rate is expected to double in eight years,trip-le in 16 years, and quadruple in 24 years. This periodic growth rate isexpected to be similar to that for the meteorology function, the forecast,shown in Figure 3.2-15, is the same as that illustrated for meteorology -(Figure 3.2-14). These data rates also will more than cover the area require-ments for the United States and are probably more representative of North andSouth America.

NAVIGATION .,

The navigation function is intended to meet the needs of maritime, air-craft, and low altitude spacecraft traffic. These needs are primarily globalrather than restricted to a geographic area such as the U.S. and its surround-ing land and water areas. Therefore, this functional forecast was developed forworld user requirements rather than U.S. user requirements.

3-29

SD 73-SA-0036-4


O'-

§•-

1: ir

1970 1980 YEAR 1990 2000

Figure 3.2-14. Meteorlogy Function Demand Mbdel

for USA

w

!•II

1 till

ui.*«r1970 1980

YtAI 1990 2000

Figure 3.2-15. Earth Resources Function Demand Model

for USA

3-30

SD 73-SA-0036-4


Reference 3-3 provides information which defines the volume of maritimetraffic and its expected growth rate of 5.2 percent per year. Reference 3-4provides the basis for estimating the amount of world transocean air trafficin 1970. Other Aviation Week and Space Technology articles have indicatedprospective traffic growth rates of about 5 percent per year. These referencesshowed that maritime traffic outnumbers transocean traffic by a factor of 250to one. It is expected that low altitude spacecraft will not contribute tothe user demand until beyond the year 2000. The tracking.and data relayfunction will provide this service in the interim period. Due to the majorityof maritime traffic, the model has been segregated into principal ocean areas.This does not infer that aircraft navigation over desolate and expansive landareas would not be supported by the navigation function.

The navigation system assumed is based on an average intermittent opera-tion by each ship about three times per hour and by each aircraft three timesper minute. These operations assume the use of a minimum of three differentnavigation satellites for minimum system operational accuracy. The assumednavigation system is*very similar to the concepts recently documented inAviation Week and Space Technology (References 3-5 and 3-6). Data-ratesshown are based on the minimum navigation system but used by all the commercialvehicles forecasted. These compensating (or offsetting) assumptions should'provide a reasonable demand model. Also in Reference 3-6, an article showeda current on-board navigation system cost of about $10,000 for transmitter,receiver, and computer. These costs are expected to reduce as communicationssystem technology is further developed making it financially attractive toinclude precision navigation sys_tems. on all commercial maritime and aviationvehicles as well as many privately-owned ships and aircraft.

Figure 3.2-16 shows satellite demand traffic from 1970 to 2000. It isexpected however, that U.S. systems tests may begin in about 1976 resulting:in an operational global system in 1980 or 1981.

AIRCRAFT CONTROL

For the same reason given in the navigation function, the aircraftcontrol function has been modeled for the world area. Data for the aircraftcontrol function are based on transocean and long-range remote area aircrafttraffic control. Aircraft control over relatively populated areas has notbeen included. Statistics on aircraft traffic were obtained from Reference3-4 and other articles reflecting prospective traffic growth rates. Datarates are based on an average four messages per hour at 30 seconds oer message(transmitted as digitized voice at a rate of 64,000 bits per second) per eachairborne aircraft. Data rates for anticipated air-sea rescue operations havenot been included because these are expected to be insignificant compared tothe normal traffic levels.

Figure 3.2-17 shows the expected satellite demand traffic data rates forthe three major ocean areas. Development of this system will occur atapproximately the same projected time period as the navigation system.

3-31SD 73-SA-0036-4


181970 1980 YEAR 1990 2000

Figure 3.2-16. Navigation Function Demand Model

For World Users

3-32

SD 73-SA-0036-4


1970 1980 YEAR1990 2000

Figure 3.2-17. Aircraft Control Function Demand ModelFor World Users

COMMUNICATIONS AND SYSTEM TEST • .

This functional category was initiated in December 1966 with the launchof ATS-1, which is still in operational service. The applications technologysatellite (ATS) series has performed development tests on the following func-tional systems: meteorology; voice communications at different .band frequencies;range-rate experiments; self-contained navigation systems; teletype andfacsimile transmissions; gravity gradient stabilization experiments; etc.Direct broadcast TV, control moment gyro stabilization systems development,laser beam optics experiments and further communications developments athigher frequencies are planned operational developments for future ATSsatellites.

3-33SD 73-SA-0036-4


The data rate model presented for the U.S. in Figure 3.2-18 has beenextrapolated from the planned ATS' capabilities at a 6 percent per yeargrowth rate. This should reasonably be representative of further communica-tions systems developments using super high frequency (SHF) and extremelyhigh frequench (EHF) bands and laser systems. The data rate presented plusthe indicated 12-hour transmission time per day is assumed to be equivalentto the total bits/day for high frequency wide band communication systemstests.

EQUIVALENT TRANSMISSIONTIME/DAY ~ 12 HOURS

1970 1980 YEAR 1990 2000

Figure 3.2-18. Communications and System Test Function Demand Model

for USA

3-34SD 73-SA-0036-4


ASTRONOMY

The geosynchronous astronomy function is based on a review of plannedU.S. applications using lower altitude spacecraft. High data rates are basedon real time TV pointing and control of observations related to spectro-heliograph and solar coronagraph experiments. Data rate growth is based onan increased demand for more observations and data as interest in this scienceexpands. The data rate is expected to double in two years, triple in fouryears, quadruple in six years, and continue to monotonically increase in thisway in each successive two-year period. These data rates are expected to bepeak steady state values for four hours per day. The demand may be met bytransmitting from several sources or at lower data rates for longer durations.Figure 3.2-19 shows the projected data rate model for this functional applica-tion.

1019_

liH

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EQUIVALENT TRANSMISSIONTIME/DAY ~ 4 HOURS

1970 1980YEAR

1990 2000

Figure 3.2-19. Astronomy Function Demand Modelfor USA

3-35SD 73-SA-0036-4


TRACKING AND DATA RELAY

The U.S. tracking and data relay satellite system (TDRSS) functions asa real time data relay link between low orbiting satellites like ERTS, Nimbus,Skylab, OSO, Code 467 and 1010 (Military), and the ground users. TDRSS willtransmit and receive high data rate information primarily in the form ofphotographs of various types. R&D satellites are expected to handle data at108 bits per second whereas future generation operational satellites may havethe capability to handle data at greater rates than 1Q8 bits per second.

As shown in Figure 3.2-20, the data rate growth forecast is based on atwo-satellite (active) R&D system and a four-satellite operational system.The estimated operational dates are based on projected demands for data relay,during the shuttle sortie, RAM and SOAR eras. Following this in the mid-1980' s, the space station will require further growth in the TDRS system torelay detached RAM data to ground users. The average growth rate from 1980to 2000 is seven percent per year. Although not shown, the data rate demandcurve includes those smaller (10? bits/second) TDRS systems for real timecontinuous planetary systems data relay in the 1980's and 1990's. As withsome of the other science and applications functions, the data rate demandcan be satisfied at lower rates with corresponding increases in transmissiontime. The data shown in Figure 3.2-20 are based on 12 hours transmissionper day.

SOLAR ILLUMINATION

The concept of solar illumination of earth from geosynchronous orbit isreceiving serious study in the area of science and technology applicationsuse of space (Reference 3-7). Solar illumination could provide useful nightillumination with a mean brightness level of one to as much as 100 full moonsby using large orbiting solar reflectors. A system concept, called Lunetta,could provide useful low-level illumination of major metropolitan areas forcrime prevention and power conservation, agricultural areas for night cropattendance and harvesting, harbors and converging shipping lanes for collisionavoidance, etc.

A forecast of light levels and locations to meet user demands cannot beestablished with the same confidence associated with each of the previousfunctions. However, it is envisioned that a 0.1 full moon demonstrationplatform will be placed in geosynchronous orbit in the 1985 to 1990 timeperiod. This would be followed in the 1990 to 1995 period by a full scaledemonstration platform providing illumination at the 10 full moon level.Figure 3.2-21 shows a system development schedule from concept formulationto operational use. Further definition of user requirements are difficult toassess at this time because they are strongly dependent on the eventualsystem feasibility. This advanced function is included in the study becauseit potentially imposes requirements for technology development missions(e.g.» ATS) during the 1980's and may also influence the definition of spaceplatform requirements in that era.

3-36SD 73-SA-0036-4

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3-37

SD 73-SA-0036-4

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3-38

SD 73-SA-0036-4


SPACE POWER RELAY

Space power relay is also an advanced concept being studied (Reference3-7) which opens a new dimension on the use of space to solve technicalproblems. The space power relay system uses geosynchronous, satellites totransfer power from remotely located power generation complexes to thepower users in major metropolitan areas. In this concept, nuclear powercomplexes are located in regions where there will be a minimum environmentalimpact. Also, solar power complexes may be located in remote solar energyintensive regions. The geosynchronous power relay satellites then becomesan integral part of the power distribution system to relay energy to thehigh energy consumption regions.

Like Lunetta, the forecast of power transfer requirements has not beendetermined in detail because system feasibility studies must first be accom-plished. Figure 3.2-22 shows the development schedule for space power relay.The two advanced technology satellites to.be flown in the 1980 to 1985 timeperiod will demonstrate small scale microwave generation, power relay, andreconversion systems. In the 1985 to 1990 era a full scale 100 megawattpower relay demonstration prototype will be placed in geosynchronous orbit.This could be followed in the mid-1990's with 10 gigawatt power relay systemsfor commercial applications. As indicated, the continued development of thisspace applications function will influence several of the ATS1 requirementsand may also influence the definition of space platform requirements in the1980 to 1990 time period.

3-39SD 73-SA-0036-4

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SD 73-SA-0036-4


3.3 WORLD AREA USER REQUIREMENTS DEVELOPMENT:i

Each of the preceding figures of functional data rate requirements arerelated to U.S. communications and science data forecasts only. An exceptionto this are the functional requirements for navigation and aircraft controlwhich are .presented on a world area user basis. Each of the other functionalmodels also needs to be extendedto a world area user basis from which a geo-synchronous satellite traffic model can be derived. The subsequent para-graphs describe the methods used to develop world area communications andscience data forecasts for the communications and data functions, the inter-national science and applications functions, and other national space programapplications functions. :

COMMUNICATIONS AND DATA TRAFFIC

The approach used to estimate world area user requirements for thecommunications and data traffic was to determine the number of world userscompared to the number of U.S. users. Then, the U.S. user data rate modelscould be extrapolated to world user models. This approach was used becausethe technology now exists to build and implement this category of communica-tions functions and, in many countries, the development of satellite communica-tions systems is a commercial venture not necessarily dependent on constrainedgovernment funding levels.

References 3-2, 3-8, and 3-9 were consulted to determine world populationand growth trends. Figure 3.3-1 summarizes the population trends from 1950to 1970 and extrapolates these growth rates to the year 2000. (This is some-what optimistic since recent growth trends in some populous countries aredecreasing markedly due to the world-wide implementation of birth controltechniques.) Figure 3.3-1 shows the population trends grouped into threemajor world areas for convenience. Each world area represents the potentialsurface area that can be covered by a single satellite. These three areasare: ,(1) North and South America including Alaska and Hawii; (2) Europe,Africa, and USSR (West) including those countries eastward to 60 degrees eastlongitude; and (3) USSR (East), Asia, Australia including New Zealand and thoseislands of the South Pacific to 180 degrees east longitude. These three worldareas encompass approximately equal land areas, but populations in each areaare consideraly different; e.g., area (1) above contains about 511,000,000people; area. (2) contains about 974,000,000 people; and area (3) containsabout 2,150,000,000 people. The approximate world total is presently about3,635,000,000 people compared to the 1970 U.S. population figure of approxi-mately 205,000,000 people.

It is further rationalized that the total population would not necessarilybe the principal users of many of the communications functions. The primaryusers are believed to be the literate population that is greater than 14 yearsof age. References 3-10, 3-11, and 3-12 provided these data on currentliteracy levels for many of the countries in each world area. Data for some

3-41

SD 73-SA-0036-4


1950 1970 1980

YEAR

1990 2000

Figure 3.3-1. World Population trend

of the countries produced educational trends which permitted the extrapolationof literacy levels to the year 2000. Using these data, an empirical expressionwas developed to extrapolate literacy growth rates by world area to the year.2000. This was:

[Literacy growth rate ^ percent/year] = [Population growth rate ^percent/year] x [1 + 2 (Illiterate Fraction)]

3-42SD 73-SA-0036-4


Fiqure 3.3-2 shows how rapidly illiteracy is being eliminated. Although notapparent from the grouped areas, there are many countries in Europe and Asiathat are more literate than the U.S. However, low literacy areas such asChina India, much of Africa, and some parts of South America increase_theworld area illiteracy averages. Based on the forecasted trend shown, theworld illiterate population will still be greater than ten percent in the ,year 2000.

'ZUJu

1950 1960 1970 1980

YEAR

1990 2000

Figure 3.3-2. World Illiteracy Trends

3-43SD 73-SA-0036-4


Combining the literacy data (from Figure 3.3-2) and the world populationdata (Figure 3.3-1) adjusted for the age criteria ( > 1 4 years old) producesthe world literate population trend shown in Figure 3.3-3. These datarepresent the primary potential users of communications and data transferfunctions. When these data are compared to the number of potential U.S.users, the ratio of world area user to U.S. user is obtained as illustratedin Figure 3.3-4. As noted on Figure 3.3-4, these data represent thepotential demand ratios.

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3-44SD 73-SA-0036-4

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3-45

SD 73-SA-0036-4


r Actual user levels, by world area, are also shown on Figure 3.3-4. Thesedata , for 1970, were obtained from Comsat reports on Intelsat usage andmiscellaneous reports of ATS usage for various communications and data trans-fer functions. As more ground terminals and distribution systems are estab-lished (covering all of the functions), the 1970 user levels (by area) willincrease toward the potential user demand ratios.

Past U.S. historical growth trends show that new technologies, such asthe telephone, telegraph, and automobile, can usually converge on demand levelswithin 30 years. Recent U.S. historical growth trends in television and com-puters seem to show a shorter convergence period to demand levels; that being15 years and 20 years, respectively. Feeling that technological developmentsin communications for some countries will lag the U.S., Europe, and Japan,a convergence period of 1970 to 2000 is assumed for each of the world areas.That is, the ratio of world area demand to the U.S. demand will increase fromthe 1970 actual user points to converge with the user demand level at theyear 2000.

A general empirical equation was developed for the time history, userlevel trends from 1970 to 2000. The equation is structured to follow thestandard historical growth pattern of any new technology, that is, an initialslope which decreases in time to meet the user population growth rate. Theempirical equation is:

RL2 = RL1 (1 + R)

where, R. 2 is the user level ratio at time 2

\1 is the user level ratio at time 1

n is the number, of years between time 1 and time 2•

R is the rate of change in user level ratio betweentime 1 and time 2

R = TT,RD1-RL1

RDe

where, RD, is the user demand ratio at time 1

RD is the user demand ratio at year 2000•

R"-, is the average rate of change in user level ratio' between time 1 and 2000

3-46SD 73-SA-0036-4


Xe

1/n- 1

Using n equal to five years, each world area user-ratio was determinedbased on the preceding equations. The resulting extrapolation ratios areshown in Figure 3.3-5. These ratios are used to extend the 14 U.S. communica'tions and data functions listed in Table 3.1-1 and defined in Figures 3.2-2through 3.2-13 to world area requirements. .

' As described, the extrapolation of the U.S. user requirements to worldarea requirements is based on the world literate population over the age. of14. To provide a point of comparison, the world to U.S. requirements ratiohas been determined on forecasted population only. This disregards age andliteracy. Using this simplified assumption, the world to U.S. ratio for theyear 2000 is 21.45 compared to 17.5 as shown in Figure 3.3-5. This assump-tion would, on the average, increase user requirements 22 percent above themodel developed.

1970 1990 20001980

YEAR

Figure 3.3-5. Extrapolation Ratios for Principal bbrld Areas

3-47

SD 73-SA-0036-4


INTERNATIONAL SCIENCE AND APPLICATIONS

The science and applications functions which lend themselves most tointernational sharing of costs and data results are meteorology, earthresources, navigation, and aircraft control. In time, probably beyond theyear 1990, international consortiums may be established to operate and main-tain geosynchronous power relay satellites.

The extrapolation of meteorology and earth resources functions from U.S.user needs to world area user needs is based specifically on the area thatcan be effectively covered by a satellite. World coverage between 76 degreesnorth and south latitudes can be obtained with four satellite locations.Sufficient longitudinal overlap is provided between satellites to permit asingle nation, (in many cases) to obtain all its data from a single satellite.Larger nations such as the U.S., USSR, and China would probably obtain datafrom two or three of the satellites, kbrld area requirements for meteorologyand earth resources, therefore, will be four times the level shown on Figures3.2-14 and 3.2-15.

The navigation and aircraft control functions, as described in the pre-vious section, were initially defined for world user needs. No extrapolationof U.S. user heeds were required to obtain the forecasted world user require-ments because readily available data were documented in terms of world userneeds.

A quantitative forecast of world user requirements for space power relayhas not been determined because this space application function will occurbeyond the 1990 time period (and is beyond the period of the current Geo-synchronous Platform Definition Study). However, the subsequent section onworld user requirements by functional spacecraft type will show a potentialnumber of 10 gigawatt satellites for world use based on a number of candidateremote power sites. The first operational satellites to be placed into ser-vice are not expected until after the year 2000.

NATIONAL SPACE APPLICATIONS PROGRAM

Some of the science and applications functions are of such a specializednature that they are most likely to be developed and operated by internationalconsortiums or under an individual national space program. The science andapplications functions which are considered as candidates for national (orconsortium) space program sponsorship are communications and systems tests,astronomy, tracking and data relay, and solar illumination (Lunetta).

The definition of world user needs for these functions based on the U.S.user requirements have been forecasted based on national space program fundingtrends. In the 1972 Forecast and Inventory Issue of Aviation Week and SpaceTechnology (Reference 3-13), space program expenditures and historical growthrates are shown for Western Europe, ELDO, ESRO, and Japan. No data werereadily located for other countries participating in space program effortssuch as Canada, China, and USSR. . It was, therefore, arbitrarily assumedthat the USSR program would be equivalent to the U.S. geosynchronous programs,and that China's efforts would be equivalent to those of Western Europe,

3-48

SD 73-SA-0036-4


and that Canada's geosynchronous participation would be equivalent to fivepercent of the U.S. efforts. Furthermore, it was assumed (with currentoptimism for the future) that the U.S. geosynchronous space program funding(government only) would grow at the rate of seven percent per year up to theyear 2000. However, European and Japanese space program growth rates wereextrapolated, from their historical values, at 15 percent per year to 1.980,12 percent per year to 1990, and 10 percent per year to 2000.

With these gross assumptions and ratios of national and-consortium spaceprogram expenditures to U.S. funding levels, Figure 3.3-6 was developed.This shows the percent equivalence of other national programs to the U.S.program which has been shown, from a U.S. user point of view, in. Figures3.2-18, 3.2-19, and 3.2-20. It is recognized that these other nations orconsortiums may not develop the same functional types of satellites whichhave been identified for the U.S. Even so, those functional satellites placedin geosynchronous orbit will be transmitting data at comparable data rates toground users. In addition, it is very likely that other countries and/orconsortiums may develop or buy their own tracking and data relay satellitesystems. This function is particularly significant because it representsabout 82 percent of the total U.S. science and applications functions datarate for 1990.

The extension of U.S. solar illumination (Lunetta) needs to world userrequirements has not been quantitatively determined because,:as for solarpower relay, this application will occur beyond the 1990 time period. Thesubsequent section on world user requirements by,functional spacecraft typewill show some typical locations where Lunetta satellites could provide someof the needed illumination benefits.

3-49SD 73-SA-0036-4

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80

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1970 1980 1990 2000YEAR

Figure 3.3-6. World National Space Applications Program Extrapolation Ratios

3-50

SD 73-SA-0036-4


3.4 W)RLD USER REQUIREMENTS BY FUNCTIONAL SATELLITE TYPE

Each of the functions which have been forecast have also been consideredfor grouping into dedicated satellite types. The grouping of functions wasbased on data sources and destinations, and frequency band allocations. for : :specific functions. International frequencies have been designated for thegeneral functions of communications, meteorology, navigation, space operationsand space research. Table 3.4-1 shows the previously listed functions whichcould be grouped. into dedicated satellite types based on these considerations.

Table 3.4-1. Functions Allocated to Dedicated Satellite Types

Satellite Type (Acronym) Functions Allocated

Intelsat Education .Commercial broadcastTeleconference (& telegraph)Post office ' • • • • - .Medical data bankBanking/bus" iness/credit transactionsNewspaper

Domsat EducationCommercial broadcastTeleconference (& telegraph)Post officeMedical data bank •Banking/business/credit transactionsNewspaperElectronic publishingCivil defenseWelfare data bankLibrary data bankPrivate record banksTelecomputations

Mersat MeteorologyEarth resources

Nacsat navigationAircraft control

3-51SD 73-SA-0036-4


Table 3.4-1 shows that eight of the communications and data categoryfunctions (Table 3.1-1) are identified for international satellite (Intelsat)transmission. It is also shown that all 14 of the communications and datacategory functions are identified for domestic satellite (Domsat) transmission.

Excluding communications frequencies which are used in Intelsat andDomsat systems, several of the science and applications functions have beengrouped on the basis of functional interrelationship and frequency assign-ments. Meteorology and earth resources satellite (Mersat) functions aregrouped because of similarities in the earth looking functions and assignedfrequencies for data transmission. Navigation and aircraft control satellite(Nacsat) functions are combined because Reference 3-6 described how voicetransmisisons could be digitized along with basic navigation data. This.advantageous.feature, useful primarily to aircraft control, could also beuseful to large harbor area ship traffic control. This could significantlyreduce the collision hazard in poor visibility conditions.

No readily apparent advantages for grouping any of the other scienceand applications functions are recognized. The remaining functions seemsufficiently different in objectives and satellite operational requirementsthat these are considered (for the new traffic model) to be performed onindividually dedicated satellites.

INTERNATIONAL/DOMSAT TRAFFIC DISTRIBUTION

Table 3.4-1 shows that eight of the communications and data categoryfunctions have been identified for transmission by both Intelsat and Domsatsystems. In addition, the data rate demand models for these functions do notdefine how much of the data rate is distributed to Intelsat and to Domsat.The subsequent paragraphs describe the rationale used to determine thisdistribution for.each of these functions. The approach used was first toestimate the year of initial operational capability (IOC) for transmission ofeach function by Intelsat. Second, the level or percentage of transmissionof each function by Intelsat in the year 2000 was estimated (using samerationale). Finally, the percentage of use between the IOC date and 2000 wasinterpolated.for each function.

The estimated year of initial operational capability and the year offirst demonstratation is listed for each Intelsat function on Table 3.4-2.It is possible that the first demonstration of business transactions andfacsimile mail transmission may have already occurred. The functions whichhave not reached operational capability lack the ground operation and distribu-tion stations required.

Table 3.4-3 presents the percentage of traffic for each function that isforecast for transmission by Intelsat in the year 2000 and the rationale used.

3-52SD 73-SA-0036-4


Table 3.4-2. Intelsat Communications Functions

Communications Function First Demonstrated Estimated IOC Year

Teleconference (& telegraph)

Commercial broadcast

Education

Banking/business/credit trans,

Medical data bank

Newspaper

Post office

1965 Early Bird

1965 Early Bird

1965 Early Bird

1971 ATS-1

1967 ATS-3

1967

T967

1974

1972

1974

1978

1978

Table 3.4-3. Estimated Percent ofIntelsat Communications to Total

COMMUNICATIONS FUNCTION

TELECONFERENCE

COMMERCIAL BROADCAST

EDUCATION

BANKING/BUSINESS/CREDIT TRANS

MEDICAL DATA BANK

NEWSPAPER

POST OFFICE

" INTELSATIN 2000

10

25

30

15

15

25

5

RATIONALE

• BASED ON (U.S.) RATIO OF INTERNATIONAL '•TO DOMESTIC PHONE CALLS PRIOR TO

. INTELSAT ' ' . ' • .

• RATIO INCREASED 5O TO ACCOUNT FOR.INCREASED TREND IN INTERNATIONAL COMM

• MORE INTERNATIONAL SPORTS* MORE POLITICAL & HISTORICAL EVENTS FOR

NEWS BROADCASTS

• INTERNATIONAL CO-OP EDUCATIONAL PROGRAMS• INCREASED DEMAND FOR BILINGUAL LITERACY

• RATIO OF EXPORT/IMPORT TO NATIONALINCOME (IN U.S.)— HAS BEEN LEVEL FOR 10 -YR

• 30'-: USE BY SMALL COUNTRIES AND 'y USE BY LARGE COUNTRIES

• FOREIGN TRAVEL AND READER INTEREST• INCREASED POPULATION ON FOREIGN ASSIGN.

• RATIO OF INTERNATIONAL TO DOMESTIC MAIL(U.S.) WITH 4VYR GROWTH RATE

• INTERNATIONAL MAIL MORE SUITABLE FORSATELLITE TRANSMISSION

3-53SD 73-SA-0036-4


The teleconference (and .telegraph) function is shown to be 10 percentinternational in 2000. In 1970 this was 100 percent international (thispercent reflects only that carried by satellite transmission) because therewere no domestic satellites at that time. This international trafficfunction began to decrease in 1972 when Brazil started using Intelsat as aDomsat and the Molniyas (Russian) and Canadian Tel sat were launched and putinto domestic operation. The predicted level is based on the ratio of U.S.international to domestic phone calls prior to the advent of communicationssatellites. This ratio is increased by 50 percent to reflect the presenttrend in increased international communications and lowered communicationscosts with satellite systems.

Of that portion of commercial broadcast carried by satellite transmissions,the amount carried by Intelsat in 2000 is estimated to be 25 percent. Until1972 it also had been 100 percent. At present, there has been world coverageof Olympics, soccer, baseball, golf, boxing, track, and other sports withothers to be added in the future. It is anticipated that more internationalevents will be televised between neighboring countries. Also, major politicaland historical events will be broadcast internationally when added networksand reduced transmission costs occur. For these reasons it is believed thatthe percentage of international broadcast will remain relatively high.

The education function is expected to grow to a level of 30 percent by2000. This estimate is based on the decreasing trend of illiteracy and theincreasing trend of international cooperative programs (i.e., business andspace). Because of the growth in multinational corporations, there is increasingdemand for bi-lingual literacy which can be met through the Intelsat culturalexchange education function.

The ratio of U.S. export/import income to total national income has beenabout 15 to 17 percent from 1960 through 1969. This ratio is believed to beapplicable in the forecast of the international to domestic banking/business/credit transaction function. The level of 15 percent is not expected tosignificantly change in the future (for the U.S.). It is noted that thisforecast is for business data transactions and does not include teleconfering(which has been previously accounted for). Other countries may have higheror lower ratios. The U.S. sample is assumed to be a representative worldaverage.

It is anticipated that low cost satellite communications will stimulatemedical data transmissions on an international and domestic basis. Mediumto small (area) countries will tend to pool their data in internationalmedical data banks in contrast to large countries (Tike the U.S.,- USSR, andChina, etc.) which will pool most of their own medical information intodomestic medical data banks. With this premise, it is assumed that smallcountries will utilize international data banks in 30 percent of their trans-missions whereas large countries will utilize international data bank infor-mation only 3 percent of the time. The integrated average of these assumptionsresults in a forecasted international to total medical data bank transmissionratio of 15 percent in the year 2000.

3-54SD 73-SA-0036-4


The international transmission of newsletters or entire newspapers forforeign distribution such as the New York Times, Wall Street Journal, Barrens,Time Magazine, and similar foreign publications is expected to be common-place in the year 2000. The percentage of international traffic to totaltraffic in the newspaper function is estimated to be 25 percent. This fore-casted demand is based on increasing foreign travel (and foreign readerinterest) projections involving an increased percent of the world populationon foreign assignments.

The international post office traffic is projected to be five percentof the total post office satellite traffic in 2000. This estimate is based onthe present fraction of U.S. international to .domestic mail with an annualgrowth rate of four percent per year. The projected growth rate is based onthe fact that the characteristics of international mail are more suitable forsatellite transmission than domestic mail.

Table 3.4-4 shows trend changes in percent of Intelsat traffic comparedto the total traffic for each of the Intelsat functions. The trend for eachfunction is interpolated between the IOC date and estimated level in the year2000 as shown in Tables 3.4-2 and 3.4-3.

Table 3.4-4. Percent of Total Functional TrafficThat Is- International .

Function

TeleconferenceCommercial broadcastEducationBanking/business/credit

transactionsMedical data bank

Newspaper

Post office

1970

100

100

0

0

0

0

0

1975

' 64\64

45

2

0

0

1980

55

55

15

11

8

: 8 .

2

1985

40

43

21

14

11

18

4

1990

,25.,34

25

45

13

22.5

1995

15

28

28

.15

14

245

2000

10

. 25 .

30

J5

15

"255

Intelsat data rates for each of the Intelsat functions were determinedusing the total function data rate and interpolated percentaces from Table3.4_4. These values for each function were summed and divided by the totalto determine the average percentage level of Intelsat traffic for the sevencommon Intelsat/Domsat functions. This trend as a function of time is shownin Figure 3.4-1.

3-55SD 73-SA-0036-4

Sp'ace DivisionNorth American Rockwell

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TOTAL INTELSAT FUNCTIONS

TWO CANADIAN DOM5ATS LAUNCHED

INTELSAT USED AS DOMSAT BY BRAZIL

1970 1980 1990

YEAR

2000

Figure 3.4-1. Intelsat Traffic Percentage for theCommon Intelsat/Domsat Functions

The step down in the curve (at the end of 1972) is caused by the use ofIntelsat as a Domsat and the launch of the two Canadian Domsats. Thisrepresents the step change in teleconference and commercial broadcast functions,The transition from 100 percent to about 65 percent actually occurs duringthe years 1972 and 1973 but has been.drawn as shown for simplicity. Thesmooth curve from 1973 has been extrapolated backwards as shown by the dashedline to 1970. This "artificial distribution ratio" is used on the Intelsatand Domsat world data rate demand curves so that there would not be a sharpstep, in these curves due to the Intel sat/Domsat transition period. It isemphasized that the total data rate demand is unchanged. The resultingfunctional demand curves will, therefore, show slightly lower than actualdemand, in 1970, for Intelsat traffic and a higher demand, that is notsatisfied in 1970, for Domsat traffic.

3-56SD 73-SA-0036-4


INTERNATIONAL SATELLITE (INTELSAT)

The world Intelsat forecast by continental area has been developed byadding each of the Intelsat functions, applying the appropriate fractionaldistribution (for Intelsat as identified i.n Table 3.4-4), and multiplying bythe extrapolation ratios presented in Figure 3.4-1. The resulting model isshown in Figure 3.4-2. Since international communications satellites providecommunications and data links between major continental areas, the data inFigure 3.4-2 have been reallocated from continental areas to satellitelocation (i.e., ocean location). Figure 3.4-3 shows these data rate modelsby ocean location. It is noted that the 1970 data rate levels are based onComsat reports of leased channel traffic hours for each ocean area but havebeen reduced as described in the previous paragraph. (The reduced amounthas been added to the world Domsat model.)

The world data rate levels shown are average values for 24 hours per day.It is recognized that real demand levels will vary from the average level.Demand levels peak during the average person's awake hours and reach a minimumduring normal sleep hours. A demand rate duty cycle has been estimated basedon the local zone time of day. Each time zone will have its maximum andminimum rates at approximately the same local time of day. Some minor varia-tions occur between nearby zones, however, because the long distance trafficto other time zones is primarily time coordinated to the best convenience ofeach party in each time zone. This effect tends to reduce daily data ratepeaks in both zones. •- :

Based on U.S. long distance telephone experience, considering time ofday rate changes and recently estimated peak traffic, mean traffic, andminimum traffic, Figure 3.4-4 was constructed. This single zone duty cycleshows that peak numbers of calls per hour average about 1.75 times the mean,number and minimum number of calls per hour average about 0.25 times the ''mean. Since telephone traffic represents more than 90 percent of all thecommunications and data rate traffic, this duty cycle is considered valid foruse with all the other functions in the category of communications and datatraffic.

Considering the time zone changes across the oceans and recognizing thattraffic also occurs in a north-south direction involving the same time zone,the peak rates over the mean for each Intelsat ocean location are:

Location

Atlantic OceanIndian OceanPacific Ocean

Peak Rate Factor

1.651.651.60

3-57SD 73-SA-0036-4

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Figure 3.4-2. World Intelsat Forecast by Continental Area

3-58

SD 73-SA-0036-4


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EducationCommercial BroadcastNewspaper • '. '_;Teleconference fc TelegraphPost Office .Medical Data BankBanking/Business/Credi t Trans.

/97O /9SOYEAR

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Figure 3.4-3. World Intelsat Forecast by Satellite.Location

3-59

SD 73-SA-0036-4


ESTIMATED R E A L TIME DEMAND RATE

12 If, 20LOCAL TIME, H O I K S

Figure 3.4-4. Real Time Communications Demand Duty Cyclefor a Single Time Zone

Experience has shown that there are a small number of users who desireto have immediate access to communication satellite links regardless of othertraffic levels. These users may only utilize satellite communications in-frequently but due to the nature and urgency of immediate communicationsaccess, a number of satellite transponders may be dedicated for this purposeonly. A typical example of this.situation is the Washington to Moscow hot-line via Intelsat and via Molniya satellite. This type of .low. volume dedicatedtransponder traffic is commonly referred to as thin route traffic. ForIntelsat operations, thin route traffic demands are about 10 percent greaterthan mean data rate levels.

At the present time there are four Intelsat IV satellites in orbit, twoover the Atlantic and one each over the Pacific and Indian Oceans. The datarate capacity, of each, satellite is 4.32 x 108 bits per second. Consideringthe peak rate factors, thin-route traffic level, and the forecasted demandlevel of Figure 3.4-3, it appears that the Atlantic satellites are operatingat about 35 to 40 percent capacity (March 1973), the Pacific satellite atabout 55 percent capacity, and the Indian Ocean satellite at 35 to 40 percentcapacity. Based on the data .rate demand slopes of Figure 3.4-3, peak capacitieswill be reached over all'oceans in the 1975-1976 time period. This demandanalysis is in agreement with the statement in Reference 3-14 which says,

3-60SD 73-SA-0036-4


"Comsat estimates that current and planned satellite communications capacitywill be saturated by 1975". The difference in time to reach peak capacitiesis due to the fact that the .1970 levels were purposefully reduced (as previouslydescribed) and the Intelsat projected demand requirements increase at anannual growth rate of.about 30 percent per year compared to Comsat estimatesof as much as 40 percent per year. For the above reasons, it is believed thatthe actual current operating capacities of the Intelsat satellites is at least10 percent higher than the demand rates shown.

DOMESTIC SATELLITE (DOMSAT)

The communications functions for the worlds domestic satellite systemsinclude all those listed for Intelsat plus those functions specifically relatedto the needs of a single nation. The world Domsat demand model includes thesum total of the 14 U.S. functional demand models minus that communicationsand data traffic computed for the U.S. Intelsat demand model. The remainingdata rates are then extrapolated to the world area demand models using datafrom Figure 3.3-5.

Figure 3.4-5 presents the world Domsat forecast by continental area. •Comparing the level of communications and data traffic of Intelsat to Domsatdemand models shows the Domsat model lower than Intelsat until mid-1982 afterwhich the Domsat model exceeds the Intelsat model becoming almost 10 timesgreater by the year 2000. This trend which lags Intelsat until 1982, isexpected when one considers the large amount of software programs and distribu-tion networks that need to be established to effectively improve the functionalservices over present methods and to perform them utilizing the expected lowtransmission costs by satellite.

The peak data rate assumed applicable to world Domsats is equal to 1.71times the mean value as shown for a single zone in. Figure 3.4-4. Since Domsatswill serve many individual small nations or a single large nation and manynation groups will span about four time zones, the peak rate of 1.71 seems tobe most representative.

Thin-route traffic demands for domestic satellite communications servicesare expected to be higher than those required for international communications.For Domsat operations, thin-route traffic demands are expected, to be 25 per-cent greater than mean data rate levels. Communications costs by .satelliteare expected to strongly influence this estimate; if costs are relatively high,the thin-route level may be only 10 percent, whereas if costs are low (asexpected), the level may even exceed 25 percent. ' , •

METEOROLOGY AND EARTH RESOURCES SATELLITE (MERSAT)

The U.S. meteorology and earth resources demand models (Figures 3.2-14and 3.2-15) have been combined and increased by a factor of four to coverfour earth zones to obtain the world Mersat forecast model. The data ratetotal for these four zones is shown in Figure 3.4-6. These data rates arecontinuous mean values with no maximum or minimum rates during the 24-hourday. Various types of information will be sensed, and'transmitted.forspecified locations in an established sequence. The sensing sequence repeatsits' cycle as each data set is completed for the zone.

3-61SD 73-SA-0036-4


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FUNCTIONS INCLUDED

EducationCommerical BroadcastNewspaper & Electronic PublishingCivil DefenseTeleconference & TelegraphPost OfficeMedical Data BankWelfare Data BankLibrary Data BankBanking/Business/Credit Trans.Private Record BanksTelecomputations

>7O YEAR ZOOO

Figure 3.4-5. World Domsat Forecast by Continental Area

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NAVIGATION AND AIRCRAFT CONTROL (NACSAT)

Combining the navigation and aircraft control models previously shown inFigures 3.2-16 and 3.2-17 provides the data rates for the world Nacsat fore-cast model. The required data rates for each ocean area are shown in Figure3.4-7. These data rates are also continuous mean values with no projectedpeak or minimum values. Since the number of traffic elements is relativelyconstant during any 24-hour period, no significant data rate variations areexpected.

APPLICATIONS TECHNOLOGY SATELLITE (ATS)

The U.S. ATS model has been extrapolated using the accumulated data fromFigure 3.3-6 to obtain the world ATS forecast. The ratio of foreign applica-tions technology satellite data rates to U.S. values is shown in Figure 3.4-8.Since these satellites are primarily for development and systems test, theexpected transmission time for the data rates shown is 12 hours. As previouslystated, satellite test transmissions at EHF and laser frequencies are expectedto .be shorter in duration and inversely proportional to the frequency band-width. .

ASTRONOMY SATELLITE

The world astronomy satellite data rate model is shown in Figure 3.4-9.The ratio of foreign to U.S. data rate is also shown. The equivalent trans-mission time shown is four hours. Some of the functions listed may requirelonger durations but at proportionally lower data rates.

TRACKING AND DATA RELAY SATELLITE (TORS)

The cumulative foreign TORS forecast model was estimated using thedata from Figures 3.2-20 and 3.3-6. These data are shown with the U.S. modeldata in Figure 3.4-10. For better global coverage it is assumed that the U.S.TDRS data rate demand grows from a two-satellite system to a four-satellitesystem in the first operational period. The equivalent transmission timeper day is 12 hours. This could occasionally increase to 24 hours per daydependent on the number of manned and unmanned flights using real time tele-vision to accomplish numerous mission objectives and operations.

SOLAR ILLUMINATION SATELLITE

The development of world user requirements for the Lunetta system havenot been projected in detail because the world-wide operational use of thissystem will occur beyond the 1990 period and, therefore, will not affect thenew traffic model. The following paragraphs are presented to provide a greaterinsight into some of the physical characteristics and a typical world applica-tion of the Lunetta system.

3-64SD 73-SA-0036-4

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An artist's/'sketch of a three-sate!! ite Lunetta system is shown inFigure 3;4-11. Lunett'a's-of-various sizes (to meet specific area illuminationrequirements) would be made up by assembling a number of standardized buildingblock reflector modules illustrated in Figure 3.4-12... Also shown in Figure3.4-12 is the general, reflector rotation requirement of 179 degrees per earthrevolution. Since the reflector satellite only completes one half of arevolution -in an orbit of the earth, it must be designed to be reflectivefrom both.sides in order to provide illumination on the subsequent orbit.This can be-visualized by following the A-B orientations shown in Figure3.4-12 around two orbits of the earth.

The illumination provided by a Lunetta on the earth's surface is primarilya function;of the reflector area and the latitude location for illumination onthe earth's surface. The illumination obtained in "full moons" as a functionof these two variables is shown in Figure 3.4-13. Listed below this figureare the desired illumination levels for various Lunetta uses.

Some of the Lunetta satellite sizing characteristics are:

Mass/reflector area. - <0.0189 lb/ft2 , iReflectivity - > 8 9 percent . . .Illumination . - 3 x 10-7 full moons/ft2 (0° latitude)Structure - Lithium framework and Lithium or

Sodium foilsConsumables. - 0.0014 lb/ft2 per year (basis - . . •

electric propulsion Isp. = 4500 sec)

Figure 3.4-14 illustrates a number of typical world locations which wouldbenefit from night illumination. System operational characteristics andtechnical analyses in greater depth are presented in Reference 3-7.

POWER RELAY SATELLITE

As with the Lunetta system, the power relay system world user require-ments have not been projected in detail since operational implementation ofthese satellites will probably occur beyond the period of concern (1990) forthe new traffic model. However, the following paragraphs are included toprovide some of this system's characteristics which could be developed onlate-1980 ATS satellites.

Figure 3.4-15 depicts a microwave reflector antenna (power relay satellite),which is reflecting an energy beam from Greenland to Western Europe. Thepurpose of the space power relay system is to uncouple power generation fromconsumption and, thereby eliminate the grographic location of consumers as theprimary influencing factor in locating power plants. This results in importantconsequences in terms of being able to utilize non-chemical energy sources(such as solar power) and in improving ecological factors (the thermal burdenfrom nuclear and chemical power plants). With the demand for increased powergeneration, it becomes even more important to strive for a more even geo-graphic distribution of thermal waste.

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Because of thermal waste problems, far northern coastal regions, near deepocean areas such as Greenland, are likely candidates for power plant locations.However the best suited locations for the transfer of solar energy into electricalpower are found in, the desert areas of the U.S., South America, North Africa,Arabia, and Australia. Figure 3.4-16 shows these global power generationregions as well as the areas requiring the use of high energy.

The power generation and transmission facility combines a power plant witha microwave transmitter system. Energy is transmitted to the power relaysatellite by a convergent microwave beam.with a power density of 4.65 w/ft2at the surface and a maximum power density of 3.40 kw/ft2 at the power (energy)relay satellite. The reflected beam, in turn, is slightly divergent so as toprovide again a safe energy density of 3.40 kw/ft2 as the beam traverses theatmosphere for a second time. The transmission frequency could be typically3 GHz (10 cm wavelength; S-band). The reflector can, therefore, be a wiregrid arrangement. Modularized construction, attitude control and solarpressure compensation, as identified for the Lunetta would also apply tothe power relay satellite.

Some of the power; relay satellite sizing characteristics are:

Power/reflector area - 3 kw/ft2Mass/reflector area - 0.015 lb/ft'Structure •' - Wire mesh and framesConsumables • - 9.3 x 10-4 lb/ft2 per year (basis -

electric propulsion ISp = 4500 sec)

A 10-gigawatt power relay satellite would have a reflector area of about3.7 x 1Q6 ft2 which .includes 10 percent transmission margins each way, Theweight would be on the order of 55,000 pounds and require about 3400 poundsper year of consumables. Ten gigawatts receiver power will require 11 giga-watts space relayed power and about 12.2 gigawatts transmitted power from thegeneration source.

Figure 3.4-17 shows the application of a global geosynchronous power relaysystem. The cases shown are examples rather than firm recommendations. TheUnited States receives power for its eastern and western industrial andmegalopolis complexes from a "Hudson Bay Nuclear Power Complex". The linesradiating from each receiver station symbolize the surface distribution net.From a "Pampa De Salinas Solar Power Complex" power is delivered to Brazil,Peru, Venezuela (and other South American nations) via power relay satelliteslocated in part'over the Atlantic and partly over the Pacific. England,France, and.West Germany draw power from a "Greenland Nuclear Power Complex"on Danish territory (a member of the European Economic Community), while Italyand Israel are among the countries drawing power from a large "Kalahari PowerComplex". Nuclear power stations in the western Soviet Union transmit powerto the large industrial complexes in their West Siberian Lowlands and deliverpower to northwestern India. An "Australian Solar Power Complex" deliversmuch needed power to the Australasian region and the western Pacific. Highlydeveloped geothermal sources in northern New Zealand deliver power as far asJapan.

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3.5 FUNCTIONAL SATELLITE CHARACTERISTICS

Up to this point the basic demand requirements imposed on the geo-synchronous orbit satellites in the new traffic model have been defined for theworld area. The next step performed in developing the satellite traffic modelwas to define the specific spacecraft characteristics used to satisfy the userdemand requirements.

Seven satellite types are used to describe the satellite capabilities forthe baseline and new traffic models. Satellite types such as solar illumina-tion and power relay are included in the new traffic model as ApplicationsTechnology Satellites (ATS) because the new model extends only to 1990.Operational versions of these functions are not expected to occur until afterthis time. The seven satellite types used are listed in Table 3.5-1 with asummary of the criteria established for each type.

For traffic model comparison purposes the criteria of earth coverage,longitudinal location, lifetime, data rate capability, redundancy, duty cycle,and thin route requirements are used with both traffic models. The number ofon-orbit active traffic elements which meet demand requirements (adjusted forduty cycle and thin route demands) depends on data rate capability, lifetime,and redundancy provided. Another criterion not shown is that satelliterecovery is possible in 1982 for both traffic models. This influences theinactive and on-ortit satellite population histories and recovery schedules.

Subsequent paragraphs define the satellite characteristics in greaterdetail and provide some of the rationale used to establish the criteria. Itis important to note that the satellite characteristics defined for the newtraffic model have purposely been selected to match those of the baselinetraffic model. This is particularly the case for Intelsat and Domsatcharacteristic data rate capability. This then permits a comparison of thetwo models and will allow significant differences to be easily identified.

INTELSAT CHARACTERISTICS CRITERIA

Earth Coverage

Ground coverage overlap between adjacent Intelsats must permit three ormore widely separated (in latitude) countries to provide communications relayservices. This would prevent interruption of relay service due to a specificrelay station outage (for maintenance, natural disaster, or political reasons)and alleviate some solar outage situations.

A minimum of three data links are required: (1) Americas to Europe/Africa/USSR (West); (2) Europe/Africa/USSR (West) to Asia; and (3) Asia toAmericas.

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3-80

SD 73-SA-0036-4


Satellite Longitudinal Locations

To meet the above criteria for coverage the following preferred andacceptable (in parentheses) range of locations for each link are: (1) 25°W(15°W-25°W); (2) 100°E (90°E-105°E); and (3) 155°W (155°W-165°W).

Lifetime

Satellite lifetime shall be seven years. Present systems design permitan operational life for this duration. Satellites launched in 1976 and sub-sequent years shall be recovered beginning in 1983.

Data Rate Capability

Twenty-four active broad-beam transponders shall be provided by eachsatellite. This value is consistent with newly proposed systems.

Sate!1i te Redundancy

Each satellite shall have sufficient on-board redundant circuits. Groundspares will be provided. This approach is less costly for systems that havelarge numbers of active on-orbit satellites.

DOMSAT CHARACTERISTICS CRITERIA

Earth Coverage

Ground coverage is required for the three major world areas includingmany of the larger islands. These areas are: (1) North, Central, and SouthAmerica including Hawaii and Alaska; (2) Europe, Africa, and USSR (West)including all countries west of 60°E longitude; and (3) USSR (East), Asia,Australia, New Zealand, and Oceana.

Satellite Longitudinal Location

The following preferred range of longitudinal locations will providecoverage .as required: (1) 135°W - 45°W; (2) 10°W - 75°E; and (3) 75°E - 180°E.

Lifetime

Satellite lifetime shall be seven years. Present systems design permitan operational life for this duration. Satellites launched in 1975 and sub-sequent years shall be recovered beginning in 1982.

Data Rate Capability

Twenty-four active broad-beam transponders shall be provided by eachsatellite. This value is consistent with newly proposed systems.

3-81SD 73-SA-0036-4


Satellite Redundancy

Each satellite shall have on-board redundant circuits. Groundspares will be provided. This approach is less costly for systems that havelarge numbers of active on-orbit satellites.

MERSAT CHARACTERISTICS CRITERIA

Earth Coverage

Sufficient coverage shall be provided to sense global Mersat informationbetween 70°N and 70°S and provide desired data to all major world areas andweather centers.


A four-satellite system meets the above criteria with location rangesas follows: (1) 60°W - 75°W; (2) 150°W - 165°W; (3) 105°E - 120°E; and(4) 15°E - 30°E.

Lifetime

In the 1975 to 1984 time period, lifetime shall be three years; beyond1984, lifetime shall be six years. Advancements in sensors can be added tothe global system earlier with the shorter lifetime criteria for the firstthree generations of satellites. Satellites launched in 1979 and subsequentyears shall be recovered beginning in 1983.

Data Rate Capacity

Increased data rate capacity will be provided in each subsequentgeneration of satellites to handle increased numbers of sensed locations anddetail. Each generation will increase by 10? bits per second (bps) such thatthe first generation set shall be capable of handling data at 1 x 10? bps,the second generation at 2 x 10? bps, the third generation at 3 x 10? bps,the fourth generation at 4 x 107 bps, and the fifth generation at 5 x 10' bps.

Sate11i te Redu ndancy

Ground spares shall be used for replacement.

NACSAT CHARACTERISTICS CRITERIA

Earth Coverage

Complete and simultaneous global coverage is required at all latitudes.

3-82SD 73-SA-0036-4


Satel 1 i te Longitu_dinal Location

Four satellite clusters with five satellites per cluster all with geo-synchronous 24-hour orbits will meet the required global coverage. The fourclusters shall be located at 0°W, 90°W, 180°E, and 90°E. The cluster shallbe composed of one geostationary satellite (at the specified location) andfour satellites uniformly distributed in 60-degree inclination orbits havingan eccentricity of 0.25. Two of the inclined orbit satellites in each clustershall maintain apogees at the maximum northern declination of the orbit whereasthe other two inclined orbit satellites shall maintain apogees at the maximumsouthern declination of the orbit.

Lifetime

Until 1985, satellite lifetime shall be five years; thereafter, it shallbe eight years. Satellites launched in mid-1977 and subsequent years shall berecovered beginning in mid-1983.

Data Rate Capacity

A capacity of 106 bits per second per satellite will handle all foresee-able aircraft and ship traffic based on the system proposed in Reference 3-6.

Satel1i te Redundancy

Each cluster can operate at full global coverage with one satellitefailure per cluster. Ground spares shall be used for replacement when twofailures in a cluster occur.

ATS CHARACTERISTICS CRITERIA

Earth Coverage

Applications technology satellites shall be positioned within line-of-sight communications with its sponsoring nation(s).


The range of longitudinal locations for those countries or consortiumswith active space programs are: USA, 105°W - 135°W; ESRO, 0° - 15°W; USSR(West), 30°E - 45°E; China, 75°E - 120°E; Japan, 120°E - 170°W.

Lifetime

. For the U.S. and USSR, ATS lifetimes will be of short duration. Halfshall be one year and the other half, two years. The remaining national spaceprogram ATS lifetimes shall be four to five years. U.S. satellites launchedsubsequent to 1980 shall be recoverable beginning in 1982. Foreign satelliteslaunched subsequent to 1981 shall be recoverable beginning in 1984.

3-83SD 73-SA-0036-4


Data Rate Capacity

U.S. and USSR satellites will vary from 0.5 x 107 bits per second to5 x 107 bits per second. Other national space program satellites will rangefrom 0.5 x 107 bits per second to 2 x 107 bits per second.

Satel1i te Redundancy

None planned. Subsequent launches may repeat mission objectives offailed satellites.

ASTRONOMY CHARACTERISTICS CRITERIA

Earth Coverage

Astronomy satellites shall be positioned within line-of-sight communica-tions with its sponsoring nation(s).


The range of longitudinal locations for those countries or consortiumswith active space programs are: USA, 60°W - 135°W; ESRO, 15°W - 30°W; USSR(West), 30°E - 60°E; China, 75°E - 120 °E; Japan, 120°E - 170°W.

Lifetime

Satellite lifetime shall be four years. This value is consistent withplanned astronomy programs. All satellites launched subsequent to 1977 shallbe recoverable beginning in 1982.

Data Rate Capacity

For U.S. and USSR astronomy satellites, data rate will increase from 107bits per second in 1978 by 107 bits per second every four years; i.e., witheach satellite generation. Other national programs will have data ratecapacity of 2 to 4 x 107 bits per second for each satellite.

Sate!1i te Redundancy

None planned.

TDRS CHARACTERISTICS CRITERIA

Earth Coverage

It has been assumed that the U.S. and USSR space program activities willgrow to the point that total global coverage will be required to satisfy thetracking and data relay requirements. The other nations and consortiums, on "the basis of funding level comparisons with the U.S. space program, willprobably need (or afford) only partial world coverage to satisfy theirrequirements.

3-84SD 73-SA-0036-4


Satellite Longitudinal Locations

On the basis of the earth coverage requirements forecasted, it isexpected that the U.S. and USSR will implement a TORS system which will growto four equally spaced .satellites. The other nations and consortiums willeach utilize two satellites located approximately 120 degrees apart and eachwithin line of sight of the owner nation. Specific longitudinal locationsare:

USA - 35°E, 125°E, 145°W, 55°W

USSR - 50°E, 140°E, 130°W, 40°W

ESRO - 55°E, 50°W (visible from Canada and Europe)

China - 60°E, 180°E

Japan ^ 80°E, 160°W

Lifetime

TORS lifetime shallrecoverable beginning in

Data Rate Capacity

be five years.1983.

All satellites are assumed to be

U.S. and USSR shall initially launch three R&D satellites with a capacityto relay data at 108 bits per second per satellite. One satellite in eachsystem shall act as an on-orbit spare or to relieve peak demand requirementsat various times. At end of life the R&D system shall be replaced by fouroperational satellites with the same data rate capacity. The subsequentreplacement generation of satellites will grow to 2 x 10^ bits per seconddata rate capacity per satellite. The other national space programs will alsoutilize satellites with initial data rate capacity of 108 bits per second withsecond generation satellites having 2 x 108 bits per second data rate capacity.

Satellite Redundancy

One on-orbit spare is used with each U.S. and USSR R&D system. Groundspares shall provide redundancy for each of the national operational TDRSsystems.

3-85SD 73-SA-0036-4


3.6 ..FUNCTIONAL SATELLITE, LOCATIONS

The preferred satellite locations for the seven satellite types servingeach country are shown in Figure 3.6-1. The Intelsat locations shown arebased on a three-system set. A four-system set would result in larger longi-tudinal location bands approximately 90 degrees apart. The individual domesticsatellites serve smaller earth coverage areas compared to the other satellitetypes. Therefore, there is more longitudinal space available from which thisservice can be provided. Also, since communications data requirements arethe greatest for this satellite type, more longitudinal space will be requiredfor the satellites (or platforms) needed to meet the demand requirements.The Mersats and Nacsats provide the desired global coverage with four longi-tudinal locations approximately 90 degrees apart. The other science andapplications satellites are geographically located to provide line-of-sightcommunications with their respective owner country. The six zones shown onthis chart are identical in location to those of the baseline traffic model.These zones are used to assess satellite population density and electro-magnetic interference which are documented in subsequent sections of thisvolume.

3-87SD 73-SA-0036-4

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3-88SD 73-SA-0036-4


C

. 3.7 TRAFFIC MODEL SCHEDULES BY SATELLITE FUNCTIONS

The new traffic model was developed using the established world areademand communications and applications requirements and the functionalsatellite characteristics. In the determination of the number of satellitesof a given data rate capability needed to satisfy forecasted demand require-ments, the peak load requirements, thin-route traffic, daily operational time,and satellite lifetime dictated the number of on-orbit active satellitesrequired for each function. As the data rate demands increased, additionalsatellites were added to meet the demands.

The following sets of figures (Figures 3.7-1 through 3.7-13) show thenumber of satellites placed on-orbit each year to meet each functional demandrequirement by world area. This results in a time-phased geographic distribu-tion of satellites for each function. Analysis of the launch time, lifetime,and satellite disposition permits the tabulation of the number of inactivesatellites on orbit,, the number of active satellites, the number of satellitedeliveries, and the number of satellites retrieved from orbit.

For example, Figure 3.7-1 shows inactive satellites on orbit by a dashedline. Active satellites are illustrated by a solid line. The point ofinitiation of the solid line represents the launch year, whereas the termina-tion point when no dashed line is shown, represents the year the satellite isrecovered. Below the bar schedule is tabulated the number of inactive, active,delivered, and recovered satellites for each year from 1970 through 1990.

Figures 3.7-1, 3.7-2, and 3.7-3 show that an Intelsat IV is launched overeach ocean area during the 1973 and 1974 time period. Previous discussionshad shown that additional satellite capacity was not required until 1975 or1976. These three additional satellites are included as shown to be consistentwith Comsat planned launch schedules. It is believed that these early launchesare to provide on-orbit backup as well as to eliminate transmission relayinterruption during "solar outage" periods occurring once a day for four daysduring each spring and fall season. This phenomenon is described in detail inVolume III. The subsequent Intelsats having 24-transponder capacity are shownbeing launched to each ocean position in the 1976 to 1977 time period. Thesesatellites are added to maintain the capability of meeting the demand require-ments as well as to replace the Intelsat IVs which have reached their end oflife.

Due to the large number of Domsats required to meet demand requirements,Figures 3.7-4 through 3.7-6 show the number of satellites required (on eachbar) for that year either as replacements for satellites at end of life ornew satellites required for increased demand.

3-89SD 73-SA-0036-4


It should be noted that for five of the seven types of satellites identi-fied, only a moderate number of satellites are required to meet user demandsup to 1990. This, however, is not the case for the Intelsat and Domsat models.With a satellite capability of fixed data rate such as 24 transponders, laraenumbers of satellites are needed to meet world user requirements in the 1985to 1990 period and although not shown, even many more satellites are requiredbeyond 1990. This indicates that communication satellites in the late 1980'sand 1990's need to have much larger data rate capability. In reality,communication satellites will have increased data rate capacity as communica-tions technology advances to meet these demand requirements. The point beingemphasized is that the 24-transponder fixed level capability was used here topermit comparison of the new traffic model with the baseline traffic model,and is not intended to reflect the best data rate capacity for the time periodof the new traffic model. Subsequent analyses related to platform requirementswill identify the recommended data rate capacity of Intelsat and Domsat plat-forms which better satisfy user requirements.

3-90SD 73-SA-0036-4


INT IINT JX\NT 31INT IIINT nrIHT mINT inIwT 3STINT nr

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O O O O O O O O O 0 0 0 0 1 1 0 1 0 ( 0 2 .

DBITA RATE CAPABILITY

3.4 * lOi1 BPS

7.Z x \{p BPS

4.^2 « 10* BP*

fi.C.4- x 1C*

Figure 3.7-1. Intelsat Traffic Model--Atlantic Ocean

3-91SD 73-SA-0036-4

ittT :jl :

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TELUTE TYPE D^TA RME ChPAB»UTY

~THT nr 7.2 « io7 BPS

IMT IB 4.i2 K IO8 BPS

Figure 3.7-2. Intelsat Traffic Model—Pacific Ocean

3-92

SD 73-SA-0036-4

1970i .

INT orINT H

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YEAR.

NO.

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o o o i i iTin' 1 \ 2 2 1 2 2 2 3 3 4 £ 6 7* MT3T5TB~

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INT UC . 4.S2 «« "0B BPS

INT "? B.M * fO* BPS

Figure 3.7-3. Intelsat Traffic Model--Indian Ocean

3-93

SD 73-SA-0036-4


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W O . RECOVERED 0 0 2 2 2 Z I I O 2 S

DATA RATE CAPA6JHTY ~ 8.64 * 10• BP5 PBR *ATEUaE~i» 8PS)

Figure 3.7-4. Domsat Traffic Model—North and South America

3-94SD 73-SA-0036-4


n|7oi .

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VEAR 1970

NO. \KIAXTWe

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19180 1990

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0 O I O I o I 0 I Z 2 .

DATA RATE CAPABILITY - 8 . 6 4 x | 0 8 B P S PER SATELLITE

(EXCEPT UK 4 W*T0~ 4.32 nlO* 6PS ASSUMED)

Figure 3.7-5. Domsat Traffic Model--Europe/Africa/USSR (West)

3-95

SD 73-SA-0036-4


1970I .

M6. ACT IMC

MO. DELIVERED

MO.

RATE

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3-96SD 73-SA-0036-4

*- 75* W <

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Figure 3.7-7. Mersat Traffic Model

3-97SD 73-SA-0036-4


»rwitwwreoNO. RECOVERED

0 OjO 0 O I I S 9 II II H 1 1 M 11 II it U

1 i a 9 \a ib& >6 » u to »» M a ae » a«I

I &h t 4 ^ 4 - 4 4 4 * 4 4 4 4 4 * 4

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~ 10* ens/secowo PERNOTt ; SATELLITE CLUSTER.

MO. INCL. ECC.I O* O4 to' .25

RECAV/ERA&L6 ( RECOVERABLE

Figure 3.7-8. Nacsat Traffic Model

3-98SD 73-SA-0036-4


1980

C «.«u*-v_i '_: •_: '.° - 3

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YEAR 1910 l?8o 1990

M O . INACTIVE O 6 O I Z 3 3 3 - * 5 5 7 8 6 a a B a s e e

N O , ACTlVJE 3 3 3 2 Z 2 3 3 3 3 3 E l t | l » t l l »

NO. DELIVERED O O O O I I I O I I O I I O I I O I 101

UO- RHC.OVEREO O O O O O O O O O O O O I O I 10 I I 0)

m OATW RATE CAPABIUTV ~ BITS/SEWWD

Figure 3.7-9. ATS Traffic Model—United States

3-99SD 73-SA-0036-4

JAP ANi »-

USSR <

BSRO <

CHINA <

WHO' > '

yy/p^.

Cf7

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NO.

NO. ACT\\ /B

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i S 5 3 3 3 4 4 4 3 i 3 3 3 2 4 4

Z I 2 0 I 2 2 I 1 0 2 2 0 1 1 3 1

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DfvTA RATE CAPABILITY ~

Figure 3.7-10. ATS Traffic Model—Foreign

3-100SO 73-SA-0036-4

V. S. 5-./C. •<.

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3-101

SD 73-SA-0036-4


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3-102SD 73-SA-0036-4

1970I ,

USSR.

ESRO

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JAPAN

VEAR. 1970

NO. I N A C T I V E

f c o . A C T i V J E

N O . D E L I V E R E D

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* DATA RATE

19 BO• 1 >

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I I I I I O O O O O O Q

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a I I I I 4 3 I

Figure 3.7-13. TORS Traffic Model—Foreign

3-103

SD 73-SA-0036-4


3.8 NEW TRAFFIC MODEL SUMMARIES

Each of the functional 'and regional tables in Figures 3.7-1 through3.7-13 have been summarized and are presented on Table 3.8-1. This shows byyear (from 1973 through 1990) the number of active,-..inactive, and totalsatellites on-orbit. .Also shown are the number of satellites delivered andrecovered in each year. The basic demand requirements show the new trafficmodel on-orbit satellite population increasing from 26 geosynchronoussatellites in 1973 to 300 satellites by the end of 1990. Satellite deliveriesper year increase tenfold from 6 in 1973 to 60 in 1990. The maximum numberof satellite recoveries is 18 per year with the number of recoveries per yearapproximately equal to the number of deliveries per year about six or sevenyears earlier.

As previously indicated, the reason for the large numbers of satelliteson-orbit and satellite deliveries in the 1985 to 1990 time period is due tothe assumption of Intelsat and Domsat fixed level (24-transponder) data ratecapacity. The assumption of 48-transponder satellites would essentiallyreduce these numbers by a factor of two. As indicated earlier, the bestselection of data rate capacity for data relay platforms is documented in asubsequent section of this volume.

Traffic model summaries, based on the previously defined satellitecapability characteristics, are shown in Tables 3.8-2 through 3.8-5 for eachcalendar year by satellite type. A table is presented for active, inactive,satellites delivered, and satellites recovered. Tables 3.8-6 through 3.8-9present similar data except that each major satellite type is further segregatedby principal area.

The new traffic model data of primary interest in physical and electro-magnetic interference analyses are the traffic model summaries by longitudinalzone. The six principal zones with respect to geographical location areidentified at the bottom of Figures.6-1. Figure 3.8-1 shows the new trafficmodel population distribution for these six principal zones. Table 3.8-10shows the tabulated values that are plotted on Figure 3.8-1. The number ofactive, inactive, and total number of on-orbit satellites are shown as afunction of year for each zone.

The largest number of satellites in the 1980 to 1990 time period isfound in Zone 2t which serves the USSR and Asia. However, since the zoneshave various longitudinal dimensions, as shown in Figure 3.8-1, it is foundfor 1990 that Zone 1 is the most crowded zone (with less than one degree oflongitude per active satellite) followed closely by Zones 2 and 4 (with lessthan 1.5 degrees of longitude per active satellite). For comparison purposes,the number of active satellites on-orbit during 1985 for the baseline trafficmodel is shown by the solid black symbol. In all zones the new traffic satellitepopulations exceed those of the baseline traffic model except for Zone 5.

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4.0 GEOSYNCHRONOUS ORBIT SATURATION

The general background..and..objectives for orbit- saturation analyseswere discussed in Part 1 of "this volume. The objectives remain the same here;namely, to determine the nature and degree of satellite congestion likely tooccur in geosynchronous orbit if the current approach of launching individualsatellites/payloads is continued through the 1990 time period. However, inthis case the analyses are focused on the traffic contained in the new trafficmodel. It is important to determine if satellite interference reachescritical levels, thereby introducing a mandatory change in program approach.This addresses the question, "are multifunction platforms required becauseof fundamental technological reasons rather than economic pressures?" Part 1of this volume treated this question for the baseline traffic model. Sincethe amount of traffic projected for the new model more than doubles thatpredicted for the baseline traffic model, the potential for satellite inter-ference and congestion is greatly increased. Thus, the orbit saturationanalyses are repeated here for the specific satellite populations and distri-butions contained in the new traffic model. Both satellite physical contentionand EM interference factors are considered.

4-1SD 73-SA-0036-4


4.1 PHYSICAL CONTENTION ANALYSIS

APPROACH

Because the new traffic model has many more satellites than the baselinemodule (413 versus 180), it requires a slightly different approach to thecongestion analysis. The ultra conservative simplified model developed toestablish satellite spacing requirements for the baseline traffic wasrestructured slightly to more closely approximate "real" satellite station-keeping capabilities. All satellites placed in geosynchronous orbit utilizeeast-west stationkeeping to offset the effects of the tesseral harmonicperturbations. However, none of the satellites projected for the new trafficmodel employs north-south stationkeeping. Thus, the satellite spacing limitswere redefined to acknowledge the three-dimensional effects of the luni-solarperturbations (orbit inclination drift). The result was applied to thesatellite distributions in the new traffic model to determine if satellitespacing requirements violated the spacing available and to assess the degreeof collision hazard.

SATELLITE .CONGESTION EVALUATION

It can be shown that for the active satellite populsions the realphysical proximity issue reduces to the consideration of individual east-west stationkeeping capabilities. Satellites placed in geostationary(synchronous equatorial) orbits at t = 0 begin immediately to be influencedby the luni-solar perturbations. Their orbits begin to precess and developan apparent inclination with respect to the equatorial plane as shown att = 1 year in Figure 4.1-1 below. This process repeats for the satellitesplaced in orbit at t = 1 year. The original satellites launched at t = 0continue under the influence of their orbital perturbations to the conditionsdepicted at t = 2 years. The satellites launched at t = 0, S0, have an orbitinclination of 1.8 degrees and a nodal shift of 13.6 degrees; those launchedat t = 1 year (Si) have an orbit inclination of 0.9 degrees and a nodal shiftof 6.8 degrees. The composite picture including the satellites launched att = 2 years is shown at the bottom of the figure.

Representative satellite around traces are shown beside each orbitalconfiguration to further illustrate the critical proximity geometry. Eventhough each satellite is maintaining its east-west position through smallmaneuvers applied at typical 10 to 30 day intervals, the orbit inclinationproduced by the luni-solar perturbations causes each satellite to follow adaily figure eight ground trace pattern as shown. Ground trace patterncharacteristics are covered in greater depth in Volume III of this report.The precise geographic location of the crossover point in the figure eightpattern is dependent upon the actual satellite location within its east-weststationkeeping deadband. This varies from day to day but follows the uniformmotion of the satellite through the 10 to 30 day drift interval across its

4-3 .SD 73-SA-0036-4


Orbit Geometry

Time = 0

Time = 1 year

Ground Traces

Equator

Stationkeeping"Deadband"

>rT 'u > / s1

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Figure 4.1-1. Geosynchronous Orbit Trendsfor Active Satellites

4-4SD 73-SA-0036-4


\ deadband. Further, the phase relationship between adjacent satellites intheir respective figure eight patterns is dependent upon their relativenodal positions. "Phase relationship" is used here to describe the relativelocation of each satellite within the loop pattern of their figure eighttraces, i.e., is one satellite at the top of a loop when the other is at thebottom, etc.? The "true" spacing limit between adjacent satellites is thusdependent upon stationkeeping capability and the phase relationship exhibitedin their ground trace patterns.

As described in Volume III, the reference plane geometry about whichthe nodal regression pattern develops is relatively fixed along the vernalequinox and is independent of satellite location. The resultant orbitalorientations are dependent only upon the time between launches and the sub-sequent interval over which the nodal regression effects are applied. Thus,all satellites launched on the same date will have the same nodal locationand will maintain a fixed relationship in their figure eight pattern asshown in Figure 4.1-2. Ground traces are shown for satellite "A" and "B"seven years after placement in geostationary orbits (maximum active lifetimes).Each has accumulated an inclination of approximately six degrees and has anodal location of 47.5* degrees retrograde from vernal equinox.

Satellite "A" would be in position A in its figure eight trace whilesatellite "B" would be at position B. In essence, they would parallel eachother around their figure eight patterns such that it would be impossiblefor satellite "B" to be at B'1 when satellite "A" was at A1. Thus, thecritical spacing is actually governed purely by the stationkeeping capabilityand is relatively unaffected by phasing mismatches which cannot occur withinthe normal mechanics of orbital motions.

To further illustrate these effects a second case pictured in Figure4.1-3 was examined. In this case satellite "D" was launched into a geo-stationary orbit six years after satellite "C" (which was presumed lauchedseven years ago). This produces a nodal separation of 40.8* degrees, themaximum which can occur within the same satellite active life constraintsutilized in the case above (7 years). However, in this case the respectiveorbit inclinations are also different. The satellite "C" orbit is inclinedsix degrees while the orbit of satellite "D" has only a 0.9 degree inclination.This affects the relative sizes of their figure eight patterns which in turninfluences their spacing requirements, but only slightly. For this casesatellite "C" would occupy positions 1, 2, 3 and 4 whiTe satellite "D"occupies positions I1, 2', 3' and 4'. Basically, satellite "D" leadssatellite "C" around its figure eight pattern by approximately one-tenthof a day. Thus, even with the worst case phase relationship achievablewithin active life constraints the actual satellite proximity characteristicsare only slightly affected, and the significant spacing requirements areagain paced only by satellite east-west stationkeeping capabilities. As shownon the figure applying a 50 percent margin to typical stationkeeping deadbanddimensions results in a realistic spacing requirement between adjacent satellitesof about 0.40 degree longitude. The 50 percent margin encompasses the phaseeffects, orbit-determination errors, etc.

*based on 6.8 deg per year nodal regression rate.

4-5SD 73-SD-0036-4


- 6°N Lat

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Figure 4.1-2. Typical Ground Trace Pattern for AdjacentSatellites Launched on the Same Date

4-6SD 73-SD-0036-4


\- 6°N Lat

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Figure 4.1-3. Typical Ground Trace Patterns for AdjacentSatellites Launched Six Years Apart

4-7SD 73-SA-0036-4


This spacing criterion was applied to the satellite populations predictedin the new traffic model. Table 4.1-1 summarizes satellite distributionsby zone for each year through the 1990 time period. Both active and inactivesatellite populations are shown where the presumption is made that allsatellites whose design life expires after 1982 (when the reusable tugbecomes available) are retrieved. First, considering only the activesatellites, the resultant average spacing within each zone is shown inTable 4.1-2 for the year 1990 when maximum population densites occur. As inPart 1, Volume IV, for the baseline traffic model, the specified satelliteoccupancy bands were used in calculating the spacing rather than the totalzonal boundary dimensions. It is shown that only zones one and two exceedthe very conservative spacing limits derived from the simplified model inPart 1 of this report. Even these offer more than a two to one margin overthe more realistic spacing requirements, 0.40 degrees, developed above.These average spacing characteristics are further defined in Section 4.2,EMI Contention Analysis, where individual satellite locations were juggledsomewhat to minimize their EM interference potential. Although in somecases this resulted in closer physical spacing than in the table above,nowhere did the local satellite crowding violate the 0.40 degrees minimumspacing limit. Thus, it is concluded that the traffic levels forecast through1990 in the new traffic model do not create a critical physical contention problem.

The inactive satellite population will be acted upon by the three-dimensional effects of orbit perturbations in the same manner as that shownfor the baseline traffic model in Part T. Their total "swept" volume willapproach the same 3 x 10^0 n mi^ defined in Part 1. Considering the entireon-orbit populsion of satellites in Table 4.1-1, the average volume persatellite is about 100 million n mi3. Further, assuming no satellite retrievalthe total on-orbit population in the new traffic model jumps from 300 to 433.Even allowing for the existing and estimated future "DoD" missions the totalbecomes 499 which averages to about 60 million n mi3 per satellite. Again,this enormous volume supports the conclusion that the satellite collisionhazard is negligibly small and that physical contention is not a problemwithin the traffic levels and distribution patterns defined in the trafficmodels up to 1990.

While it is concluded that satellite physical congestion is not acritical problem with the hi ah traffic levels predicted in the new trafficmodel, this conclusion applies only temporarily. At some point in the future theavailable space in geosynchronous orbit will be fully utilized, particularlyin the zones over the land mass regions. Some form of grouping and hardwareretrieval will be required. Even with the rapid advancement of communica-tions technology and the widening of the usable EM spectrum, thus providingmajor increases in unit capabilities, the available geosynchronous spaceis finite and eventual crowding will occur. Long before this, however,rigorous planning, coordination, and internation cooperation will be requiredto preclude serious interference conditions even within the traffic levelsprojected by the study.

4-8

SD 73-SA-0036-4

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4-9SD 73-SA-0036-4

,§pace DivisionNorth American Rockwell

Table 4.1-2. Active Satellite Spacing for New Traffic Model (1990)

ZoneMaximum Number ofActive Satellites

Actual SatelliteSpactng

1 Europe/Africa(0° - 45° E)

2 Asia/Australia(45°E - 165°E)

3 West Pacific(165°E - 165°W)

4 East Pacific(140°W - 165°W)

5 North/SouthAmerica(45°W - 140°W)

6 Atlantic(0° - 45°W)

47

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1.7 deg/satellite

4-10

SD 73-SA-0036-4


4.2 EMI CONTENTION ANALYSIS

The EMI contention analysis for the new traffic model followed the samelogical flow as that performed in Part 1 for the new baseline traffic model.A more complex problem existed because of the much larger number of activesatellites. Adjustments to the zonal locations were necessary to arriveat the best spacing -- again for the C-band data relay satellites -- to ensurethat the most favorable conditions existed for use in the EMI analysis.

The results show that an all C-band data relay system cannot functionwithin the limits of interference levels recommended by CCIR. Only Zone 5could be made to perform within the limits. This would require 97-foot(instead of 60-foot) ground antennas. It is necessary, therefore, toexamine alternate solutions. One solution is to utilize two higher fre-quency bands, each on different satellites, and .alternate the frequenciesfrom one satellite to the next. Sufficient spacing can be accomplished toprovide interference levels under the limits with this technique. Anotheralternate is to combine the capabilities of all three bands (C, K|_g and KH!)on a platform and service the traffic with a greatly reduced number ofsatellites. This technique provides the capability for even greater spacing.However, careful planning must be exercised to ensure the proper trafficdistribution service.

The baseline traffic model comments for other frequencies and DoD-typesatellites apply also to the new traffic model. Only one new type mission isprojected for this model; that is the added navigation data in the Nacsat--navigation and traffic control satellite. Its characteristics arecovered in the following section.

SATELLITE RF CHARACTERISTICS

The basic RF characteristics of the new traffic model elements are thesame as those of the baseline traffic model with the exception of the Nacsat.The baseline system for aircraft navigation and traffic control was based onan Aerosat-type system. Aerosat supported the traffic control and communica-tions function with only geostationary orbital satellites. In the new trafficmodel, a system utilizing both geostationary and inclined orbit satellites ina constellation-like system of 4 to 11 satellites was projected. Both DoD andFAA are presently studying such systems. More details for this system areincluded in Section 4.4 of Volume V. Table 4.2-1 outlines the basic RF char-acteristics of a projected system.

4-11SD 73-SA-0036-4

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SATELLITE DISTRIBUTIONS BY FREQUENCY BAND

The satellite distribution process for the new traffic model was consid-erably more complex than the baseline model. A total of 239 active satellitesis projected by 1990 for the new traffic model. This compares to 68 for thebaseline traffic model. Of the 239 satellites considered for the new trafficmodel, 190 are data relay types, either Domsat (146) or Intelsat (44). Moredetailed distribution analysis was necessary to optimize the soacing in eachof the six zones.

A further breakdown of the traffic model to define the specific area cov-erages required was performed. Figure 4.2-1 shows this breakdown. Results ofthis analysis allowed redistribution of the 70 Domsats for USSR (east), Asia,Australia and Oceana from a spread of 105 degrees (75°E to 180°E) to 154 degrees(16°E to 170°E). Similar expansion of distribution was accomplished for otherzones.

Figures 4.2-2 through 4.2-6 display the results of distribution analysesof the C-band data relay satellites for optimum spacing. These figures alsoshow the satellites operating on other frequency bands (S, VHF, UHF and Ku).Their distribution was controlled to provide maximum overall physical spacingconsistent with mission location requirements.

Table 4.2-2 lists the resultant spacings by frequency band and overallphysical density. Minimum C-band satellite spacing of 0.8 degree was presentin Zone 2 for the 18 Indian Ocean satellites. If these were spread, intoadjoining areas (a possibility), the minimum spacing could possibly be increasedto 0.9 degree. At the same time, the spreading would impact the adjacent areasand reduce their spacing from the 1.5 degrees and 1.3 degrees as Presentlyprojected in Figure 4.2-3.

An examination of the individual zonal charts indicates that the minimumphysical spacings exist only at very few locations. The 0.4-degree minimum inZone 2 exists at only two positions: where the TDRS and astronomy satellitesare interspersed with the Indian Ocean Intelsats. S-band satellite minimumspacings were shown. Maximum sparings were not meaningful with the smallnumbers of satellites projected.

EMI MODEL, CRITERIA AND ANALYSIS

The 11-satellite C-band model described in the baseline traffice model(Section 4.2) was used as the basis for the new traffic model EMI analysis. Asindicated by Table 4.2-2, the maximum spacing for C-band satellites was 3degrees and the minimum was 0.8 degree. Using the CCIR interference levelcriteria and referring to Figure 4.2-8 of Section 4.2, Volume IV, Part 1, itis easily shown that only the 3-degree spacing sections could be supportedwithin acceptable interference levels. At this spacing, a 97-foot antennawould be required at the ground stations. Other lesser spacings could notbe supported with feasible size ground antennas at C-band. Table 4.2-3 liststhe interference levels for various spacings utilizing 98-foot antennas.

4-13SD 73-SA-0036-4

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Table 4.2-3. Interference Levels Versus Zonal SpacingsT98-foot Ground Antennas)

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RECOMMENDED SOLUTIONS

Since it is feasible in the 1980-1990 era to utilize higher frequencybands for data relay systems, an alternate multiband system could provide asolution. One solution would be to alternate satellites using C-band, K(_Q-bandand Km-ban'd in geostationary orbital positions. Two results occur: (1) spac-ing between like frequency satellites increases over the minimum spacing fora singular frequency band system, and (2) the Km-band satellite gives seventimes the data relay capacity. The K^-band satellite replaces seven C-bandsatellites, thus reducing the density and allowing greater spacing.

An example of alternate frequency band position application was developed.In this case, the minimum spacing zone (Zone 2) with 0.8 degree spacing is usedwhere the three bands are positioned for maximum spacing at the desired bands.C-band satellites need the most spacing since ground antenna discrimination ismore difficult at the lower frequency. As pointed out in Section 5.5 of Vol-ume III, sharper beamwidth antennas can be obtained at the higher frequencies.The factor, antenna diameter over wavelength, determines the beamwidth and thusthe allowable spacing of satellites.

In Zone 2, the new traffic model shows 18 C-band satellites between 90°Eand 105°E. The equivalent total traffic is 432 transponders (18 x 24). Thistraffic requirement can be supported by two KHr-band (168 transponders each),two C-band (24 transponders each) and two K|_Q-band (24 transponders each)satellites as shown in Figure 4.2-7.

C-band satellites were used to obtain the broader earth coverage thatresults at the lower frequency. Broader coverage is needed for some channelsto provide broadcast-type service. The resultant alternate solution in Zone 2provides 15-degree spacing for the C-band satellites and 6-degree spacing forboth the KLQ- and Km-band satellites. These spacings (see Figure 4.2-8 ofPart 1) provide interference levels well within the CCIR recommended limits.

4-21SD 73-SA-0036-4

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Another alternative is to place the three frequency band systemson one spacecraft or platform. Such a platform would have a capacity of 216transponder channels. Two of these platforms could then replace 18 of thereference C-band satellites. Spacing could be adjusted to the maximum consist-ent with service areas and adjacent zonal services. C-band becomes the limitingfrequency band. A minimum of 4.6-degree spacing could be allocated and stillremain within the allowable interference levels.

4-23 SD 73-SA-0036-4


5.0 GEOSYNCHRONOUS REQUIREMENTS ASSESSMENT

Analysis of the new traffic model indicates that other than a largeincrease in the numbers of satellites, the only fundamental change is in thenavigation and traffic control satellite (Nacsat). The new traffic modelreflects the potential entrance of many nations of the world into geosynch-ronous programs. Additional Intelsat (Comsat), Domsat, TORS, and astro-physicssatellites are proposed to reflect this multi-national interest. In the caseof the Nacsats, the concept is significantly different from the baselinetraffic .model. Instead of only data relay service, the Nacsats also providenavigation and surveillance functions.

Section 5.1 reiterates the satellite characteristics, by functionalgroup, that were used in establishing the traffic model. The only significantdifference between the characteristics of the inventories of the two trafficmodels is the power requirements of the Nacsats which is approximately 2 kilo-watts. The characteristics associated with the astro-physics satellitesreflect the observational platform synthesized for the baseline traffic model.

Grouping criteria such as'global coverage, solar noise outage, uniqueorbital placement, orientation, and mission equipment compatibility thatestablished the minimum complement of platform types for the baseline trafficmodel are equally applicable to the new traffic model. One additional type ofplatform is identified. The Nacsat concept requires four constellations ofplatforms that are centered approximately 90 degrees apart in longitude.Each constellation requires one geostationary element and four elements ininclined geosynchronous orbits. Because of the unique placement requirement,the functions of Nacsat are not groupable with other geosynchronous functions.

Operational and system level requirements for the data relay and Nacsatplatforms are different than for their baseline traffic model equivalent. Thecommon support module (utilities platform), TORS, and observational platformrequirements are the same for both traffic models. Coverage requirements areessentially the same for the data relay platform but the expanding demand fordata relay service results in the requirement for as many as eight platformsto service one global region. Both the expanded data relay platform require-ments and the Nacsat platform requirements are presented in Section 5.3.

The on-orbit servicing design criteria are the same for both trafficmodels. The criteria were intentionally developed to reflect the idiosync-rasies of the servicing mode rather than the type of platform or configuration.An abbreviated summary of the criteria developed in Part 1 of Volume IV ispresented in Section 5.4.

5-1SD 73-SA-0036-4


5.1 SATELLITE INVENTORY ANALYSIS

As a prelude to .the definition of platform "requirements for the newtraffic model, it is helpful to briefly examine the inventory of satellitesand their important characteristics. The basic geosynchronous program require-ments for the new traffic model were derived from forecasts of user needs.The satellite populations filling these needs were established principallyto aid in comparing the scope of traffic represented by the two models, sincethe equivalent user demand data were not available for the baseline trafficmodel. Thus, while the satellite populations were somewhat arbitrarily con-structed for the new model and their characteristics were patterned closelyto those in the baseline traffic model, a further look at these characteristicswill contribute to a better understanding of the differences in platformrequirements for the new model traffic.

PROGRAMMATIC DESCRIPTIONS

The overall geosynchronous program requirements derived for the newtraffic model included consideration of 22 major functions, many of which werestructured from related groups of subfunctions. . Many of these functionsrepresent differences in the parameters treated and modes of individual useroperations, but they can utilize common mission equipment installed in geo-synchronous satellites. This is particularly true for communications relayservices involving various types of information transfer; i.e., voice, video,digital, etc. The total population of satellites in the new trafficmodel was grouped into seven basic types or categories, generally reflectingcommon mission equipment. Also, the nature of the mission equipment,(whetherit serves a mature operational function or is principally tailored for develop-mental functions)was considered in defining the seven categories. A briefdescription highlighting the important features of each satellite type ispresented below. Corresponding satellite types in the baseline traffic modelare identified where appropriate.

Intel sat

The Intelsat satellites provide international commercial communicationservices. These include:

Tel conferenceCommercial broadcast (TV)Business/credit transactionsNewspaper transmissionPostal servicesMedical data bankEducation programming

5-3

SD 73-SA-0036-4


Growing user demands through the 1990 time period are reflected in a risingsatellite population (44 active satellites in 1990). Each satellite consistsof a 24-transponder, C-band unit, having a total data relay rate capability of864 mega-bits per second. The Intelsat satellites correspond to the "Comsats"identified in the baseline traffic model with one exception. The Comsatswere considered to be only 12-channel transponder satellites.

Domsat

The Domsat system provides domestic commercial communications servicesdealing with internal traffic within individual nations or economic/culturalblocks of nations. National needs reflect an expansion of the internationaltraffic elements to encompass functions pertinent to local activities.These include:

Teleconferencing ,Commercial broadcast (TV),Business/credit transactionsNewspaper transmissionPostal servicesMedical data bankEducation programmingCivil defenseWelfare data bankLibrary data bankTelecomputationsPrivate record banks

Rapidly growing user demands through the 1990 time period result in theDomsat population being the largest group of any satellite type. A total of146 active Domsats are projected for 1990. Each satellite consists of a 24-transponder, C-band unit, having a total data relay rate capability of 864mega-bits per second. The Domsats correspond to the "U.S. domestic" and"foreign Domsats" identified in the baseline traffic model. Note that in thebaseline traffic model foreign Domsats were considered to be only 12-channeltransponder satellites.

Mersat

The Mersat system provides global meteorology and earth resources services.They are operational in nature and include the following functions:

MeteorologyMineral and land resourcesAgriculture, forestry, and range resourcesWater and marine resourcesSoil differentiationTopographic informationMaterials location

5-4SD 73-SA-0036-4


A system of four active satellites provides global coverage. Increasing datacapacities are projected through the 1990 time period as the demand for specificdata grows and new, more productive sensors are developed. Data rates up to50 mega-bits per second were defined. The Mersats .correspond to the "operationalearth observation" satellites in the baseline traffic model.

Nacsat

The Nacsat system provides world-wide navigation and traffic controlservices to ships and aircraft traversing the oceans and desolate land massregions. They are operational in nature and handle both navigation signalsand enroute planning and control information. Local traffic control aroundharbors and airports is not included. Because of the large number of individualusers (each ship and/or aircraft), simple, relatively low-cost equipment waspostulated for the terrestrial elements of the system. To achieve the desiredaccuracy with low-cost equipment,simultaneous access to navigation signals frommore than one satellite is required. This,combined with-the need for coverageof the polar air routes, resulted in a Nacsat system comprised of four constella-ions of five satellites each. Four of the satellites in each constellation arein inclined elliptical orbits with the fifth located in a geostationary orbitsuch that it is the center of symmetry in the ground trace pattern of theremaining satellites in its constellation. Data rate capability for eachsatellite is projected to be one mega-bit per second. The Nacsats correspondto the "navigation and traffic control" satellites identified in the baselinetraffic model.

Advanced Technology Satellite (ATS)

The advanced technology satellites provide a basic test bed for the develop-ment of space-related technologies. These include furthering design techniquesand gaining experience in new modes of operation. Potential specific functionsare communications development for direct broadcast operations, the design ofequipment for higher frequency bands such as SHF, EHF, and laser applications,and developmental testing of satellite support systems, spacecraft retrievalconcepts, and on-orbit module replacement. A total of five active advancedtechnology satellites is projected for the 1990 time period servicing bothU.S. and foreign space program needs. Data rates up to 50 mega-bits persecond for each satellite are projected. The ATS's in the new traffic modelcorrespond to the entire family of development/test satellites identified inthe baseline traffic model (advanced technology, system test, developmentalearth operations, and small ATS).

Astro-Physics

The astro-physics satellites provide a basic on-going capability forconducting astronomy and space physics programs which can advantageously beimplemented at geosynchronous altitudes and which supplement related terrestialand low-orbit operations. Although they are research-oriented, they areconsidered to be operational because their objectives are centered in datagathering rather than sensor development. Specific functions include:

5-5

SO 73-SA-0036-4


Solar astronomyStellar/X-rayPlasma physicsHigh energy physicsRadio astronomy

A total system of six active astro-physics satellites was projected to satisfyboth U.S. and foreign space program needs in the 1990 time period. Data ratesup to 40 mega-bits per second for each satellite are projected. These satellitescorrespond directly to the astro-physics satellites identified in the baselinetraffic model.

Tracking and Data Relay Satellite (TORS)

The tracking and data relay satellites provide the communications linkbetween the ground and orbiting spacecraft for tracking signals and the relayof real-time or recorded data. This is similar to the U.S. TORS functionidentified in the baseline traffic model, but has been expanded to includeforeign space program needs. Growth to an active population of 14 satellitesis predicted.

SPACECRAFT CHARACTERISTICS

The principal characteristics of the satellites in the new trafficmodel are essentially the same as those of the baseline traffic model. Certaintypes of satellites (ATS, TORS, astro-physics) were considered as only U.S.sponsored in the baseline traffic model. The new traffic model expands thesponsorship to include foreign space elements also.

The one change of significance between the satellites of the two trafficmodels are the updated navigation and control satellites. The baseline modelincluded only traffic control data relay functions on this satellite. Thenew traffic model satellite includes navigation data, surveillance, and datarelay. Also, five satellites are required for each global region.

Table 5.1-1 summarizes the characteristics of the satellitesof the new traffic model. The characteristics associated with Mersat andastro-physics satellites are a compilation of the most stringent characteristicsof the same types of satellites in the baseline traffic model.

5-6SD 73-SA-0036-4

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•5 .2 MISSION OBJECTIVES' GROUPING

The primary factors that influenced the mission objectives grouping ofthe baseline traffic model satellites are equally applicable to the satellitesof the new traffic model. These factors are summarized in Table 5.2-1.

Table 5.2-1. Functional Grouping Considerations

Consideration

Global Coverage

Solar Noise Outage

Unique Placement

Orientation Requirement

Sensors and System ConceptDevelopment

Impact

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Minimum of 2 data relayplatforms per region

Non groupable-independentplatform configurationof satellite

Separation of fixed andscanning local verticalmission equipment; separ-ation of inertialpointing mission equip-ment.

Independent satellites;not recommended forgrouping with in-servicecommercial equipment.

The detailed rationale associated with each consideration is presented inSection 5.2, Part 1 of Volume IV. The resultant theoretical minimum number ofplatforms into which the new traffic model can be functionally grouped is sum-marized in Table 5.2-2. Technology and mechanization limits will expand theactual number of data relay platforms required to 23 (see Section 5.3).

The non-groupability of the Nacsat satellites stems from the uniqueplacement requirements of the satellites. There are four constellations offive satellites each. The constellations correspond to the four globalregions for world-wide coverage. One satellite out of each group ispositioned in a precise geostationary orbit; the other four satellites inthe group are positioned in an inclined geosynchronous orbit with pre-determined separations. Figure 5.2-1 illustrates the relative location of

5-9SD 73-SA-0036-4


Table 5.2-2. Theoretical Minimum Functional Grouping Inventory

Platform Type

Data Relay

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Astro-Physics

TORS

SatelliteEquivalent

Intel stat; Domsat

MERSAT

NACSAT

Astro-Physics

TORS

Total

Inventory

8

4

20

12

14

58

the Nacsat constellations. With this arrangement, navigation,surveillance and data relay functions can be provided on a world-wide basis, including the polar air routes.

The ATS or developmental satellites are not grouped with any of theplatforms for the same reason as in the case of the baseline traffic model.Identification of developmental equipment for the 1980 time frame is imprac-tical , and even if it could be defined it is not considered advisable tocombine essentially experimental equipment/operations with commercial opera-tions that society has become dependent upon.

Theoretically, only one astro-physics platform is required for eachnational space program (U.S. and two major foreign powers). However, thetraffic analysis and platform synthesis for the baseline traffic modelindicated four independent sets of astro-physics payloads would be requiredto satisfy the complete program of geosynchronous astro-physics operations.The requirements for these payloads could be met either with a total inven-tory of 12 astro-physics platforms or by periodic changeout of mission equip-ment with on-orbit servicing operations (on each of three platforms).

The TORS platform inventory also reflects the required complement ofboth U.S. and foreign platforms. The reduction in space element inventoriesbetween the satellites and platforms is a result of consideration of the on-orbit servicing of the platform concept.

5-10SD 73-SA-0036-4


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5.3 GEOSYNCHRONOUS PLATFORM REQUIREMENTS

The common support module or utilities platform approach and themulti-function platforms were evaluated for the new traffic model justthe same as for the baseline traffic model. The common support module,TORS platform, and observational platform requirements for the new trafficmodel are identical to those for the baseline traffic model. The pro-liferation of Intelsat (Comsat) and Domsat data relay functions in the newtraffic model significantly changes the requirements for this type ofplatform. The expanded capability of the navigation and traffic controlplatforms also results in some unique operational and system level require-ments.

COMMON SUPPORT MODULE

The only satellite in the new traffic model that has a significantlydifferent support requirement than its counterpart in the baseline trafficmodel is the navigation and traffic control satellite (Nacsat). TheNacsat requires approximately 2 kw of power. This requirement does notperturb the common support module concept derived for the baseline trafficmodel; it was anticipated that some satellites and platforms would requireup to 2 kw power eventually. A "plateau" design requirement was specifiedfor the electrical power system. The requirement was to synthesize 500 w,1 kw, 1.5 kw, and 2 kw electrical power subsystems.

The other support functions to be included in the common supportmodule are: (1) pointing, (2) stabilization, (3) data processing, and (4)impulse/propulsion. -Table 5.3-1 lists the selection^of the most stringentfunctional requirements from the inventory of satellites.

Table 5.3-1. Common Support Module Functional Requirements

Function

Electrical powerPointing QStability Q)Data handlingPropulsion

Requirement

2 kw10 arc seconds1 arc second/second50 megabits/second70 pounds hydrazine

The pointing and stability requirements reflect the'capability of centralized hardware. Accuracies morestringent than specified must be accomplished byinclusion of the sensor directly in the control loop.

DATA RELAY PLATFORMS

As expressed in the EMI contention analysis, one concept to supportthe new traffic model utilizes the full capability of three assignedfrequency bands for data relay functions on a single space platform. Full

5^13SD 73-SA-0036-4


capability at each band is postulated by using 36 MHz transponder channelsspaced 40 MHz apart, and providing channel overlap transmission by usingorthogonal polarization. By use of orthogonal polarization transmission,the frequency band occupancy is doubled.

A platform utilizing this concept would have the following totaltraffic capability expressed in numbers of transponder channels.

• C-Band. 24 channels• KLQ-Band 24 channels .• Kni-Band --•• 168 channels• Total Platform 216 channels

Other frequency reuse techniques on the platform could be used ifnecessary. One technique is to use time division multiple access (TDMA)combined with multiple beams and beam switching. This concept provides flexi-bility to account for peak needs in specific areas. It is particularlyadvantageous when the higher frequency (KLQ and KHI) Dands are used withnarrow beams (*>-2 degrees).

Continental United States is a prime example where four 2-degree spotbeams can be used, each to illuminate an area that roughly corresponds tothe four U.S. time zones. By use of beam-switching, the variable trafficdensity distribution with time of day and night can be accommodated.

The major frequency reuse technique utilizes orbitally spaced platforms.Spacing is sufficient to allow ground station antenna discrimination. Thisspacing can be a minimum of 4.6 degrees for 60-foot antennas and 3 degreesfor 97-foot antennas. These data are expressed for C-band, 24-transpondersystems, the limiting frequency band on a multiband platform system.

All of these frequency reuse techniques are necessary platform systemrequirements to meet the new model traffic needs.

Multiple KHI platforms each with 168 available transponder channelscould meet the traffic requirements of most world regions. C-band systemsare, however, considered necessary to provide wide geographical coveragewith feasible on-board RF power levels. Wide area coverage is necessaryfor point-to-area broadcast-type service. At C-band, all of the U.S. canbe covered with a shaped beam antenna with a four-watt RF power outputtransmitter. A TV program, for instance, originating in New York,can bebroadcast on a single C-band transponder channel and picked up by any orall ground stations in the continental United States. If a higher frequency(KLO or KHI) were used, where the 2-degree spot beams are maximum, it wouldbe necessary to use four channels for each spot beam. C-band serves auseful purpose in efficiency of spectrum use for this type of broadcasttransmission.

- band systems are used in the same manner as Kni-band systems; i.e.,with 2-degree spot beams. K|_Q-band adds 24 channels to a data relay platform.The Domsat-type function requires maximum data relay capacity. Intelsat datarelay platforms can be postulated with 192 channels each and still supportthe traffic needs with a reasonable number of units. Thus, Intelsat platformscould operate with KHI- and C-band only (168 and 24 channels, respectively).

5-14SD 73-SA-0036-4


Multiple platforms are advantageous for several reasons. One is to pro-vide continuous, but reduced capacity, operation during solar outages. Thiswas explained in detail in the baseline traffic model section. Another is theinherent redundancy provided by the use of more than one platform. Trafficcan easily be directed to other platforms during down times associated withregular maintenance or with fault correction. It is also advantageous to.support growth and the gradual traffic increase by using the capability toplace platforms in orbit as they are needed.

The 1990 zonal distribution of all geosynchronous satellites Wasgiven for the new traffic model in Section 4.2. A set of five charts(Figures 4.2-2 through 4.2-6) defined the satellite distribution for the six

these zonal charts for the Domsat and Intelsata table of distribution by zone and by service area,the numbers of satellites for each service area

support by zone and identifies the orbital position location limits foreach service area. These data are used to develop the regional platformrequirements. Domsat traffic was determined by analysis of service areatraffic on the basis of numbers of equivalent C-band transponder channels(assuming 24 channels per C-band satellite). The four regions that wereestablished for global coverage for the baseline traffic model are alsoapplicable for the new traffic model. The area coverage and longitudepositions of the regions are listed in Table 5.3-3.

Table 5.3-3. Regional Characteristics

zones. Examination ofsatellites resulted inTable 5.3-2 identifies

Region

III

IIIIV

Longitude

172°E68°E6°W

110°W

Domsat

Eastern Asia/AustraliaIndia/ChinaEurope/AfricaNorth/South America

Intelsat

Trans-PacificIndian OceanTrans-PacificNorth/South

America

The first step in the analysis was to assign the service areas to theregions compatible with regional platform coverage. Because of regional over-laps, certain service areas could be covered from either of two regions. Inthose cases, assignments were based on a combination of the most compatiblecoverage (highest ground antenna elevation angle or mask angle) and an attemptto equalize regional traffic. It was also important to ensure that any singlecountry could be covered from one regional orbital location. This groundrule was used to preclude the requirement on ground stations for separate wideantenna pointing angles for its Domsat service access. Table 5.3-4 shows theresults of this analysis. Each region is displayed with a tabulation of (1)regional service areas, (2) their associated traffic in terms of transponderchannels, (3) the orbital limits for service area coverage, (4) regional totaltraffic, (5) regional number of platforms, and (6) resultant total regionalplatform capability.

5-15

SD 73-SA-0036-4

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5-17SO 73-SA-0036-4


The regional number of platforms (5) is calculated by dividing theregional total traffic in terms of transponders (4) by 216 (the capabilityin transponder channels of a three-band platform). This results in thefollowing number of Domsat platforms in the four global regions for 1990:

.Region

Number of platforms

I2

II

6

I I I

5

IV

4

Orbital position placement of these platforms is predicated on a spacingof 5 degrees with a mixture of Domsat and Intelsat platforms. Compatibilitywith service area coverage is strictly observed. Five-degree spacing waschosen to ensure interference levels within allowable limits. Except forRegion I, there are sufficient platforms to preclude solar outages of morethan two links simultaneously. Platforms spaced 10 degrees will provide pro-tection from this event. Actual Domsat locations were not chosen until afterthe Intelsat analysis was completed and the number of its platforms defined.

A similar analysis was made of the Intelsat platform requirements. TheIntelsat problem is considerably simpler. Only three regions require Intelsatcoverage, i.e., Regions I, II, and III. Intelsat requirements for Region IVfor North/South America can be serviced from either Region IV Domsats (excesscapacity exists) or partially from Region III Intelsats. Examination of theIntelsat traffic discloses the following regional traffic distribution (1990):

Region

IIIIII

Area

Pacific OceanIndian OceanAtlantic Ocean

C-Band24-ChannelReference

151811

Numberof

Channels

360432264

EquivalentPlatforms

222

Capability

384384300

The capacities of Intelsat platforms are based on the use of C- andKHl-band systems only. These two bands provide the capability for 192transponder channels. C-band is used to provide area coverage so that lowtraffic density locations may be included. KHI is used to provide spotbeam illumination to high traffic density locations. K|_Q-band was not pro-posed for use because of its low additional capacity (24 channels) and theproblem of providing wide area coverage. In the case of Region II, additionalcapacity can be obtained from frequency reuse on Km-band widely separatedbeams. Region III requires one full Intelsat platform (24 C-band, 168 KHJ-band) and one Intelsat with 24 C-band channels and 84 (no dual polarization)Km-band channels.

Platform position locations were developed by combining regional Domsatand Intelsat platforms adjacent to each regional position identified and inter-spersed to ensure optimum area coverage. Figures 5.3-1 through 5.3-4 defineorbital positions of these platforms and their service areas.

5-18SD 73-SA-0036-4


120E 150E 150W 120W

-

o

COVERAGE LIMITS(5 DEG MASK ANG E)PLATFORMS AT: '

^62E 177E

Platform

Domsat I

Domsat II

Intelsat I

Intelsat II

Location(degrees)

162E

172E

167E

177C

Service Area

.Japan, USSR (Cast)[Australia, New Zealand[Indochina, East IndiesIPhillipines

Japan/Cliina/USSR (East)lEast Indies/Australia/New Zealand| andU.S. /Canada /Mexico

PlatformCapabi 1 i t.v ,Channels

216

216

192

112

RegionCapabi I i ty ,Channel s

432

384

Figure 5.3-1. Region I - Data Relay Platform Locations

5-19

SD 73-SA-0036-4


3 E 60E 90E 130E 150E

90E

Platform

Domsat IDomsat 11

Domsat IIIDomsat IVDomsat VDomsat VI

Intelsat I

Intelsat II

Location(degrees)

55E75E

65E80EBSE90E

60E

70E

Service Area

India

China

China/India/ArabiaAfrica/Europe/Indochina/Austral ia/East Indies

PlatformCapability,Channels

216216

216216216216

192

192

ReqionCapability,Channels

1296

381

Figure 5.3-2. Region II - Data Relay Platform Locations

5-20

SD 73-SA-0036-4


60W 30W 3QE

Platform

Domsat I

Comsat 11

Domsat III

Domsat IV

Domsat V

Intelsat 1

Illtl-lS.lt II

Location(degrees)

10U

0

5E

IDE

15E

15W

W

Service Area

Europe

Europe, Afr ica

) EuropeAfr ica

| USSR (West)

1 Canada/Europe/i A f r i ca /U .S .A .•South Anwru.i

PlatformCaoani I i ty ,

Channels

216

216

216

216

216

108'

11?

RegionCapabil ity,

Channels

1 080

100

*K|([-band H4-cnannel stnqle polart/iltion only

PL15E

TFORMS AT-

Figure 5.3-3. Region III -

Data Relay Platform Locations

5-21

SD 73-SA-0036-4


180W 150W 120W 90W 60W

COVERAGE LIM(5 DEG MASK

120K

Platfonn

Domsat 1Dom'..it IIDoK.lt III

Domsat IV

1 (ji.,1 lion(deqrees)

120Wi iswMOW105W

Service Area

) U . S . A .1 C.m.id.i( M e x i c o

South America

I'}. it fnnnC.in.iln l i ty.

Channels

216?I6216216

RcqinnCtipahi 1 i tv .

Channel *v

H64

Figure 5.3-4. Region IV - Data Relay Platform Locations

5-22

SD 73-SA-0036-4


In all cases., care was taken to locate Intelsat and Domsat platforms sothat any Intelsat coverage and, where possible, single country coverages byDomsat were protected from solar outages. This was accomplished by alternatepositioning so that a minimum of 10-degree spacing between these platformsresults. As previously mentioned, 10-degree spacing will preclude simultan-eous solar outages. Region II is an ideal example. For example, figure5.3-2 shows the 10-degree Intelsat platform spacing, the 20-degree IndiaDomsat platform spacing, nominal- 5-degree spacing for three China Domsatplatforms, and 15-degree spacing for a fourth China Domsat platform. Allof this was accomplished while still maintaining ground locations for therequired functions within the 5-degree mask angle. Volume V, Section 4.4,defines the development of the platform hardware and the concepts forcoverage of the desired service areas.

TRACKING AND DATA RELAY PLATFORMS

The baseline traffic model proposed a single tracking and data relaysatellite (TORS) system for the U.S. only. The new traffic model expandsthe use of geosynchronous satellites for the relaying of data from lowearth orbit satellites both for the U.S. space program and foreign spaceprograms. The only difference between the two traffic models is the numberof satellites; neither the type nor functions are different. Therefore, thesystem requirements are the same as those of the baseline traffic model TDRS.

Operationally the foreign TDRS concept will obviously be different.Longitudinal positions will be dependent upon the single national groundstation selected. The longitudinal separation and zones of exclusion will benumerically the same but obviously geographically different. None of thesedifferences will affect the platform synthesis.

The system level requirements for the TDRS platform are the same as forthe satellites of both the baseline and the new traffic models. They areas follows:

Low data rate relay -

Medium/high data rate relay -

Low data rate uplink -

10 kbps simultaneously from20 low earth orbit spaceelements

50 Mbps simultaneously to/from2 low earth orbit spaceelements

10 kbps to one low earth orbitspace element

Low data rates are accomplished via VHF (136 to 138 MHz) for the downlink andUHF (400.5 to 401.5 MHz) for the uplink. Medium/high data transfer betweenthe TDRS and the space elements utilizes S-band (2.025 to 2.1 GHz uplink;2.22 to 2.28 GHz downlink) or Ku-band (14.81 to 14.91 GHz uplink; 13.85 to14.0 GHz downlink). All TDRS to/from ground data relay is accomplished atKu-band (13.4 to 13.64 GHz uplink; 14.6 to 15.2 GHz downlink).

5-23SD 73-SA-0036-4


OBSERVATIONAL PLATFORM REQUIREMENTS

The observational satellite characteristics assumed for the new trafficmodel reflect the observational platforms that were synthesized for thebaseline traffic model. It was pointed out in Section 5.3 of Part 1 of VolumeIV, that there was an inadequate definition of U.S. geosynchronous observationalsatellites. , Therefore, as part of this study a representative model was developed.The new traffic model considers both U.S. and foreign observational satellites.Obviously, if adequate definition of the U.S. space elements is unavailable,definition of foreign satellites will be even less definitive. For purposesof this study it is assumed that the foreign observational platforms areidentical to those synthesized as part of the baseline traffic model.

As a result of the analyses associated with the baseline traffic model,the four major discipline classes that lend themselves to multifunctionalgrouping are:

Earth observationsSolar astronomyStellar astronomy ..Plasma and magnetospheric physicsHigh energy physics

The composite system requirements which are the same for both trafficmodels are reiterated in Table 5.3-5.

Table 5.3-5. Observational Platform Requirements

Function Requirement Driver

Orientation

PowerPointing

Stability

Data handlingImpulse/propulsion

Scanning local verticalInertia!

2 kw10 arc seconds

1 arc second/second

50 Mbps

70 pounds hydrazine

Earth observationsAll except earthobservationsEarth observationsStellar/solarastronomyStellar/solarastronomyEarth observationsEarth observations

5-24SD 73-SA-0036-4


NAVIGATION AND TRAFFIC CONTROL PLATFORMS

The system defined for the baseline traffic model utilized a singlegeostationary satellite in each region and was patterned after the Aerosatconcept. Its purpose was to provide a communications link between aircraftand ground for traffic control and general communications. The systemconceived for the new traffic model is considerably more complex. Byutilizing a. constellation of satellites, in geostationary and inclinedgeosynchronous orbits, navigation and surveillance functions are alsoprovided to the user.

Both DoD and FAA are presently studying constellation type systems foroperational use in the 1980 time period. Constellations range from the DoDconcept of a five-satellite system with one geostationary and four-inclinedgeosynchronous orbit spacecraft to an FAA concept of two geostationary andnine inclined orbit satellites. Four such constellations would be needed forglobal coverage with the DoD concept; three would be required with the FAA concept,

Constellation type systems are necessary to provide the navigation andsurveillance functions with sufficient precision and time continuity at anypoint in the regional coverage areas. Use of several inclined orbit satellitesprovides this capability by allowing aircraft and/or ships to "see" severalspacecraft at any given time. Multi-point navigation and surveillance informa-tion is used to generate accurate position information.

For the new traffic model a five-satellite constellation system similarto the DoD system is, defined. This system was chosen because of its betteradaptability to global service. The FAA concept, with 11 satellites for CONUSand four more geostationary satellites for the oceanic areas, was more specif-ically defined for air navigation and traffic control of aircraft flightsassociated with U.S. traffic. Four constellations located approximately at0°, 90°E, 180° and 90°W provide global coverage. This system would enableproperly equipped users, at any global position, to determine position atany time of day. Figure 5.2-1 illustrates these constellations and the earthpattern track traced by the inclined orbit spacecraft. With this type globalsystem, six satellites would be in view of users more than 80 percent ofthe time. Fifty percent of the time, at any specific latitude, eight satelliteswould be in line of sight. For navigation purposes, only four satellites needbe in view of the user.

Each of the satellites generate a PN (pseudo random noise) codethat would be received by the user for comparison with his own on-boardgenerated signal. This determines range to the specific satellite by theamount of time delay. Repetition to the measurement three times yields threedimensional position information of the user. Velocity data could be acquiredin a similar manner by tracking Doppler information. A signal from the geo-stationary satellite is used to correct the user's clock. User positionaccuracy will be in the order of 100 feet or less, less than one foot persecond velocity, and within nanoseconds of time. Navigation information canbe acquired in less than one minute.

5-25SD 73-SA-0036-4


User navigation is the primary requirement for the Nacsat platform.Surveillance—for traffic control--and two-way user/ground communications(both voice and data) must also be accommodated. Each satellite must, there-fore, provide the necessary subsystems to effectively perform these functions.

In summary the functional requirements of a Nacsat platform system are:

1. Navigation: The platform must provide information signals toaircraft/ships to enable the user to calculate a position fix.The information consists of range data between the plat-forms and the user, and the precise ephemeris data of the plat-forms as originated from the ground stations.

2. Surveillance: Platforms must 'be capable of relaying groundcontrol initiated interrogation signals to each userindividually. Measurement of elapsed time until a responsefrom each user is received is the primary data utilized.Elapsed time measurement is performed by the ground station.The platform provides the space link.

3. Communications: This function is essentially the same as inthe baseline traffic model. The platforms must relay bothvoice and digital data between users and a ground controlcenter.

Functional Parameters

The platform parametric requirements for the navigation, surveillance,and communications functions are listed in Table 5.3-6.

Table 5.3-6. Nacsat Platform Requirements

Function

NavigationSurveillanceSurveillanceCommunications

(digital data)Communications

(digital data)Communications

(voice)Communications

(voice)

Link

Platform/aircraftPI atf orm/ai rcraf t

Platform/groundPlatform/aircraft

Platform/ground

Platform/ground

Platform/aircraft

No. ofChannels

1111

1

25

25

Bandwidth (MHz)Per Channel

2020205

15

0.025

0.025

Total

2020

20

5

15

0.625

0.625

5-26SD 73-SA-0036-4


These requirements stem from the data relay loads imposed by the traffic con-trol system. Two mass functions size the required oarameters: (1) surveil-lance samples per unit time to be processed, and (2) message/bit rate requiredfor air-to-ground communications.

These requirements and their frequency band allocations are shown on thepictorial chart, Figure 5.3-5.

Summary

A five-platform constellation type system was selected for thenavigation and traffic control system. It is similar to a system presentlybeing considered by DOD. This system provides global coverage with a totalof 20 platforms. It provides the necessary continuity of contact with usersin any region for the navigation, surveillance, and communications functions.Since each constellation consists of one geostationary and four inclinedorbit geosynchronous platforms, it was decided to make a separate Nacsatplatform usable for any of the constellation units. For the proper globalcoverage, it is also necessary that these platforms be placed at 0°, 90°E,180° and 90°W, or as closely thereto as possible.

5'27 SD 73-SA-0036-4

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5-28

SO 73-SA-0036-4


5.4 ON-ORBIT SERVICING CRITERIA

The servicing modes for the platforms associated with the new trafficmodel are the same modes as for the baseline traffic model equivalanet plat-forms; auto-remote and both pressure suited and shirtsleeve manned attendance.No unique requirements on the platform design were defined as a result of theexpanded satellite inventory of the new traffic model. All functions are thesame.

The platform requirements and rationale are developed in Section 5.4,Part 1 of Volume IV. A condensed summary of these retirements is presentedherein.

CONFIGURATION REQUIREMENTS

Overall size, shape,and arrangement of the platform must provide forservicing access by the selected system. In the unmanned case, this meansthat the platform must allow a manipulative device to qrasp, remove, andwithdraw any replaceable unit and, subsequently, to insert and install itsreplacement. This could be accomplished by either removal external to thesurface of the platform or through an: annular structure (docking ring) whichprovides adequate clearance for the largest package and articulation motionsof the manipulative device. Clearances must also consider possible use ofportable (manipulator-mounted) lights and TV for remote operations. Thisconcept also implies a manipulator end effector, which has sufficient accuracyand rigidity to grasp special latching mechanism for module interchange andactuation of electrical and plumbing auick disconnects.

For the manned approaches, clearance requirements for internal accessmust consider the man in a suited envelope, and his movement through passage-ways and docking ring with replaceable units, tools, etc. Package installationcan be conventional ground-type, latches or disconnects, but with allowancesfor additional clearance and loss of dexterity due to a gloved hand.

SUBSYSTEMS REQUIREMENTS

The various requirements imposed on the subsystems differ with theservicing approach. Shirtsleeve servicing requires the greatest number ofprovisions including a pressurizable compartment, atmospheric control (orman-module interface), lighting, voice communication, crew aids,and protectiveprovisions. EVA/IVA requires similar but fewer provisions in that life supportand environmental protection are furnished by the pressure garment assemblies.All concepts require a form of docking for rigid attachment, interface con-nections to the service unit, data links for trouble analysis and checkout,and a capability to deadface or shut down systems or equipments undergoingreplacement. For the manned modes, the latter could consist of manualswitches and valves. For the remote mode, ground commands could be input viathe service unit or directly to the platform.

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Various schemes could be employed for diagnostics, test, and checkout.Status data to the level of the replaceable unit are required at the aroundstation prior to the servicing mission to ensure adequate delivery of spares.It would seem feasible that the ground station would periodically checkoutsystems for trend data and confidence checks. The platform must, at aminimum, be compatible with these requirements with higher levels of built-intest capability optional for operational needs.

EVOLUTIONARY CONSIDERATIONS

It appears that an evolutionary servicing concept is appropriate for aplatform program. Initial module replacement can be achieved by the auto-remote concept. As the platform program progresses, repairs and refurbish-ment will probably be required and more complex and intricate operations willbe necessary. This type of activity is more amenable to man attendance. Theprojected development of the tug supports the evolutionary concept. InitialIOC of the shuttle and unmanned tug supports the early phase of on-orbitservicing of platforms at the modular interchange level. Approximately fiveyears after initiation of platform operations, a man-rated tug 'is planned.This timing would support potential refurbishment of platforms.

In order to minimize total program development effort, it is recommendedthat the platform be designed to an integrated set of servicing requirements;a single concept that will accommodate remote, EVA.and shirtsleeve servicing.In this approach, the servicing mode evolves, not the platform design.

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6.0 REFERENCES

3-1. Hough, R.W., A Study of Trends in The Demand for InformatiorrTransfer,Stanford Research Institute, SRI Project MU-7866 (February 1970).

3-2. Long, Luman H., The 1972 World Almanac and Book of Facts, New York:Newspaper Enterprise Association, Inc.(1971).

3-3.. Klass, Philip J., "Maritime Satellite Economics Studied", Aviation Weekand Space Technology, 1 May 1972, pp. 52-55.

3-4. Ray and Ray. "1970 Air Passengers Between the United States, OtherCountries by Flag of Carrier", Aviation Week and Space Technology,26 July 1971, pp. 32-33.

3-5. Miller, Barry, "USAF Studies NAVSAT Proposal", Aviation Week and SpaceTechnology, 8 May 1972, pp. 50-57.

3-6. Klass, Philip J., "Promise Seen for Hybrid ATC", Aviation Week and SpaceTechnology, 18 September 1972, pp. 52-56.

3-7. Ehricke, Krafft A., Use of^Shuttle in Establishing Large Space Installations,Space Division, North American Rockwell Corporation, SD 73-SA-0015(January 1973).

3-8. Hammond's World Atlas, Maplewood: C.S. Hammon & Co., Inc. (1964).

3-9 "Population", Encyclopedia Britannica, Volume 18, (1966), p. 234.

3-10. The Europa Year Book 1971, Vol. I., London: Europa Publications Limited(1971).

3-11. The Europa Year Book 1971, Vol. II., London: Europa Publications Limited(1971). ~

3-12. "Illiteracy", Encyclopedia Britannica. Volume 11, (1966), p. 1088.

3-13. Miscellaneous Space Budget Growth Trends, Aviation Week and SpaceTechnology, 13 March 1972, pp. 33-43.

3-14. "Extended-Capacity Intelsat-4 Planned in Hughes-BAC Study", Aviation Weekand Space Technology, 11 September 1972, p. 19.

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