apollo experience report electronic systems test program accomplishments and results

8/8/2019 Apollo Experience Report Electronic Systems Test Program Accomplishments and Results

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N A S A T E C H N I C A L N O T E

LOAN COPY: REAFWL (DO

KIRTLAND AF

- N D-6720

APOLLO EXPERIENCE REPORT -ELECTRONIC SYSTEMS TEST PROGRAMACCOMPLISHMENTS A N D RESULTS

by T h o m a s E . OhnesorgeManned SpacecrufiCenter

. .

Hozlston, Texas 77058

- " 1' , < _ , i , . , .. .N AT I O N A LA E R O N A U T I C SA N D SPACE ADMINISTRATION WASH IN GTON ,O: c. :- M A R C H~e,n

\.- L ...

, 8


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TECHLIBRARYKAFB, NU

0333390". . . ..

1.ReportNo .- . ..

2.overnm ent Accession No . 3. Recipient's Catalog No.

NASA TN 0-6720 '..i . ~ . - ~ ~~

A Titla and Subtitle..

APOLLO F X P E R I E N C E RFFORTELFCTRONIC S Y S " S TEST PROGRAMACCOMPLISHMENTS AND RESULTS

5. Report Date

.~ ~ - .- . . .

7. Author(s)

~ ..

8. Performing Organization Rep ort No.

Thomas E. Ohnesorge, MSC MSC S-28310. Work UnitNo .

~~

9. Performing Organization Name and Address 914-13-00-00-72

Manned Spacecraft CenterHouston, Texas 77058

11 .Contract orGrant No.

I

" .13. Type ofReport and Pwiod Covered

12. Sponsoringgency Name andddress Technicalot e

National Aeronautics and Space AdministrationWashington, D. C. 20546 I14. Sponsoring AgencyCode

1- .

15. %-pplementary Notes- - ~~~

The MSC Director waived the us e of the International %Stem O Units (a) orthis Apollo Experience Report, because, in his judgment, use of SI Units would impair the usefulnessof the report or result in excessive cost.

- ~i " . - -16. Abstract

This document presents a chronological record of th e Electronic Sys tems Test Pro gram from i tsconception in May 1963 o December 1969. The origi nal concep t of t h e program, which was pri-mar i ly a spacecraft/Manned Space Flight Network communications sys tem compatibility and per-formance evaluation, is described. The evolution of these concepts to include various levels oftest detail, a s well a s systems-level design verif icat ion test ing, is discussed. Actual implemen-tation of th ese con cept s is presented, and the faci l i ty to support the program is descr ibed . Tes tr e s u l t s a re given, and significant contributions to the lunar landing mission ar e underl ined. Plansfor modifying the facility and the concepts, based on Apollo experience, are pr op ose d.

Apollo Telemet ry. Communications System Ranging* S y s t e m s Te s t ' Command* Command Module Television

Lunarodule ' Voice

19. Security Classif. (o f this report1. ., . "" - - .~~~~ "

20. Security Classif. (of this page) -121. NO. of Pages I 22. Price*None I None 75 I $3.00- "

"o r sale by t he Na t iona l Techn ica l In fo rmat ion Se rv ice , Spr ingf i e ld , Vi rg in ia 22151


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CONTENTS

Section

SUMMARY . . . . . . . . . . . . . . . . . . .INTRODUCTION . . . . . . . . . . . . . . . .

Backgr ound and Purpo se of Thi s Docume nt

History of the Test P r o g r a m . . . . . . . .PROGRAM CONCEPTS AND DEVELOPMENT

TES T ACTIVITIES . . . . . . . . . . . . . . .Major Tests . . . . . . . . . . . . . . . . .Specia l Tes t s . . . . . . . . . . . . . . . .Support Tests . . . . . . . . . . . . . . . .

SIGNIFICANT RESULTS . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

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. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

Command and Service Module Block I-E Test (A-1) Result s . . . . .Command and Service Module Block 11 (Simulated) Test (A-2) Resu l t s

Saturn IVB CCS Test (A-3) Results . . . . . . . . . . . . . . . . . . .

Command and Service Module Block I-D Test (A-4) Resul ts . . . . .Command and Service Module Block I1 Gros s Tes t (A-5) Resul t s . . .Lunar Module Gross Test (A-6) Results . . . . . . . . . . . . . . . .Apollo Lutlar Surface Experiments Package Gross Test (A-7) Results

Apollo Communicat ions System Phase I Test (A-8) Results . . . . . .Apollo Communicat ions System Phase I1 Test (A-9) Results . . . . .

Apollo Range Instru mentati on Aircraf t Test (A-10) Results . . . . . .Apollo Communicat ions System Phase 111 Te s t (A-11) Results . . . .Additional S-Band Test (B-1) Results . . . . . . . . . . . . . . . . .Special FM Test (B-2) Results . . . . . .. . . . . . . . . . . . . . .

P a g e

1

2

2

2

6

1 0

11

25

38

45

. . . . 46

. . . . 46

. . . . 47

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. . . . 48

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Section

Antenna Static Test B-3) Results . . . . . . . . . . . . . . . . . . . . . . .Frequency Modulation Demodulator Threshold-Extension Test

(B-4) Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Spli t -Phase PCM Test (B-5) Results . . . . . . . . . . . . . . . . . . . . . .Extravehicular Communications System/USB System Design

Verif icat ion Test B-6) Results . . . . . . . . . . . . . . . . . . . . . . .Apollo 9 Mission Configuration Voice Demonstration (B-7) Results . . . . . .Apollo 8 Miss ion Tes t (B-8) esu l t s . . . . . . . . . . . . . . . . . . . . . .Lunar Module Color TV Te st (B-9) esu l t s . . . . . . . . . . . . . . . . . .

Apollo Lunar Surface Experiments Package Command Anomaly Test(B-10) Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Apollo Lunar Scientific Data System/MSFN Design

Verif icat ion Test (B-11 ) Results . . . . . . . . . . . . . . . . . . . . . . .Support Test (C-1 to C-21) Results . . . . . . . . . . . . . . . . . . . . . . .

PLANS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CONCLUDING REMARKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPENDIX A

.EST PROGRAM OPERATIONS . . . . . . . . . . . . . . . .

APPENDIX B . ELEMETRY AND COMMUNICATIONS SYSTEMS DIVISION,COMMUNICATIONS SYSTEMS ENGINEERING ANDTES T BRANCH LABORATORY. EST P SUP POR TCAPABILITY . . . . . . . . . . . . . . . . . . . . . . . . .

Page

49

50

50

50

50

50

51

51

51

51

52

54

55

57

iv


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ACRONYMS

AAP

ACAM

ACC

ACS

AGC

ALSEP

AM

AMQ

APL

ARIA

ASE

A S P 0

ATC

ATP

BER

CAM

CCB

CCDC

ccs

CDR

CDDT

CM

COMSAT

CRO

Apollo Applications Program

Apollo computer address matr ix

antenna control console

Apollo communications system

automatic gain control

Apollo lunar surface experiments package

amplitude modulation

analog-mult iplexer-quantizer

Applied Physics Laboratory

Apollo range instrumented aircraf t

audio support equipment

Apollo Spacecraft Program Office

Apollo time cond itione r

acceptance test procedure

b i t e r r o r rate

computer address mat r ix

Configuration Control Board

central control and display console

command and communicat ions system

command distr ibut ion rack

Countdown Demonstration Test

command module

Communications Satellite Corporation

Carnarvon, Austral ia

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CSM

cv

DRUL

DSE

EASEP

E1

EKG

EMU

ESCF

ESTL

ESTP

ET R

EVA

EVCS

F M

FMFB

FOD

GSFC

H . L .

IAM

ICD

IPM

IRIG

IU

J P L

KSC

command and service module

command verification

down-range up link

data storage equipment

ea rl y Apollo scientific experiments package

Engineering Instruction

e lec t rocard iogram

extravehicular mobility unit

Electronic Systems Compatibility Facility

Electronic Systems Test Laboratory

Elec t ronic Sys tems Tes t Program

Eastern Test Range

extravehicular astronaut

extravehicular communications system

frequency modulation

F M feedback

Flight Operat ions Directorate

Goddard Space Flight Center

hardl ine

incidental amplitude modulation

Interface Control Document

incidental phase modulation

Int er- Range Instrumentation Group

instrument unit

Je t Propulsion Laboratory

John F. Kennedy Space Center

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LE M

LM

MCC

MCC-H

MGC

MILA

MPS

MSC

MSFC

MSFN

NASA

NRZ-L

PAM

PCM

PLSS

PM

PMD

PRN

PSK

RC

RER

RSSC

SBED

SBER

sco

SDD

lunar ,excursion module

lunar module

Mission Control Center

MCC-Houston

manual gain control

Merr i t t I s land Launch Area

miss ion prof i le s imula tor

Manned Spacecraft Center

Marshall Space Flight Center

Manned Space Flight Network

National Aeronautics and Space Administration

nonre turn to zero- leve l

pulse amplitude modulation

pulse code modulation

por tab le life suppor t sys tem

phase modulation

payload module decoder

pseudorandom noise

phase shift key

res i s tor-capac i tor

rece iver exc i te r ranging

remote-s i te s imula tor console

serial bit e r r o r detec tor

subb i t e r ro r rate

subcar r ie r osc i l l a tor

signal data demodulators

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SPA

ssc

SSTC

TAR

TCSD

TDC

TDP

TOB

TV

UDB

UDL

USB

USBSS

vco

VOGAA

V R

WI

s i gna l -p roce s so r a s s emb ly

space- su i t communica tor

s pacec r a f t sy s t em test console

turnaround ra t io

Telemetry and Communicat ions Systems Division

test d i r ec to r conso l e

t r ack ing da t a p roce s so r

tel eme try output buffer

television

updata buffer

updata link

unified S-band

USB sy ste m sim ula tor

vol tage-cont ro l led osc i l l a tor

voice-operated gain-adjusting amplifier

ver i f ica t ion rece iver

word intel l igibi l i ty

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APOLLO EXPERIENCE PEPORT

ELECTRON1 C SYST EM S TEST PRO GRA M

ACCO MPLISHM ENTS AND RESULTS

By Tho ma sE. O h n e s o rg eMann ed S pacec ra f t Ce n t e r

S U M M A RY

The Elec t ron ic Sys tems Tes t Program descr ibed in th i s document was es tab l i shedto fulfill a need that developed as manned space-f l ight communicat ions systems evolvedin complexity and required capability. The combining of all communications functionsinto one unif ied communicat ions system for the Apollo Program, instead of the mult iplecommunica t ions sys tems tha t were used on Projec t Mercury and the Gemini Program,necessitated the innovation of a combined systems test ing concept . For the f i rs t t ime,a concept of simu lta neo us spacecraf t / spacecraf t /g round conlmunications system testingw a s es tab l i shed a s a fundamental portion of communicat ions system development andperformance verif icat ion. The interact ion and combinat ion of al l information on on eradio-frequency carr ier required compatibi l i ty verif icat ion and performance evaluat ionof the syste m prior to manne d f l ight . The fact that each type of spa cec raf t w a s manu-fac tured by a di ffe ren t cont rac tor and tha t the ground communica t io ns sys tem w a s pro-v ided by severa l d i ffe ren t sources in tens i f ied th i s need for combined sys tems tes t ing .

The test program began with the f i r s t system scheduled to f ly - hat is , thecommand and service module Block I ( e a r t h -o rb i t a l ) sy s t em - nd the Manned SpaceFlight Network equipment required to support these missions. The program progressedto testin g of more advanced systems and complex combinations of th es e sy st em s tof ina l ly a r r ive at the lunar landing communications system configuration . During thisprogr essio n, speci al test in g of cr i t ical information channels and channels containingupdated hardware occur red . A few major compatibi l i ty problems were detected andcor rec t ive ac t ion de te rmined . Many minor problems were no ted and so lu t ions recom-mended. Testing techniques and concepts were developed and evolved as t h e t e s t p r o -g r a m p r o g r e s s e d .

Th e res ul ts of the test program have vindicated the combined systems compatibi l -i ty approach for communicat ions system development and test ing. The conduct of theprogram, including peripheral areas of supp ort , has del ineated the need for betterspecif icat ion and test ing criteria, as well as f o r sy s t ems t e s t i ng on a b readboa rd ba s i sprior to design f inal izat ion.


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During the first 24 month s of it s existence, f ive s ignif icant events occurredwithin the ESTP. First, construction of a faci l i ty to house the ESTP at MSC was ap-proved by NASA Headquarters . This faci l i ty was off icial ly design ated the ElectronicSystems Compatibility Facility (ESCF). The laboratory area within this facility inwhich the actual systems test ing takes place was subsequently designated the ElectronicSys tems Tes t Labora tory (ESTL) . In the in te r im, a t emporary fac i l i ty loca ted a t MSCwas autho rized and subse quen tly used until the summe r of 1966. Second, support and

ass is t anc e agre eme nts wit hin MSC and with oth er NASA Cent ers wer e reach ed. Th eseag reemen t s , as modified by experience and by changes in funct ional responsibi l i ty, aresummar i z e d n a b l e I. Th i rd , a dec is ion was made o eli min ate est ing of GeminiProgram communica t ions because he ime frame o manned aunch was oo c losefor avai la bi l i ty of proper equipment , because he rf sys tems nvolved were essen-t ia l ly he same as those for Project Mercury (even hough he elemetry and com-mand sys tems using thesc? links were different) , and because he ime or designfinalization of Apollo hardware was apidly approaching. Coupled with his eventwas a decision o el iminate all plans for es t ing any vhf or hf sys tem s s in ce hes esy st em s had not changed signif icant ly in several years; however, this decision waslater modified for special instances. Fourth, a Jet Propulsion Laboratory (JPL) DeepSpace Network (a JPL-NASA network for unman ned satellites and probes) unified S-band

(USB) receiver-exciter-ranging (RER) system, modified for Apollo frequencies andpa rame te r s , w a s made ava i l ab l e t o t he ESTP in Sep t embe r 1964 , a l ong w i th commandand ser vic e modu le (CSM) Block I equipment, so tha t sys tems tes t ing could begin inNovember 1964. Early test ing of the se i t em s was ne ce ss ar y so that any problems en-countered could be reso lved and the necessary modi f ic a t ions could e incorpora ted in tot h e s y s t e m p r i o r t o t h e f i rs t manned Apollo f l ight . (The J P L RER syste m was repla cedby a production-model MSFN RER sys tem in ear ly 196 5. ) Fifth, in January 1965, onthe bas is of cost an d MCC operat ion schedules, the plans to incorporate the MCC in thetest loop were dropped at the reques t of NASA man age men t. Speci al tests involving theMCC h ave been performed, however; a nd addit ional tests wil l be pe r fo rmed at th espe cif ic req ues t of the MSC F light Opera tions Direc torat e (FOD) .

While the ini t ia l purpose of the ESTP was, as s ta ted ear l ier, to provide in forma-t ion regarding spacecraft /ground telecommunicat ions system compatibi l i ty and per-formance based on tests with operational equipment, t h i s purpose has been broadenedsomewhat to include design verif icat ion test ing, mission anomaly invest igat ions, pre-launch problem resolut ion test ing, and exploratory and dev elopment tests to improvesys tem s per fo rmance . These and o ther aspec ts of the test p r o g r a m a r e descr ibed inthe following sections.

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TABLE I. - ELECTRONIC SYSTEMS TEST PROGRAM PARTICIPATION

Respons ib i l i t i es

Imple mentat ion of ESTP and ESTL

Negotiat ion and coordinat ion of procu remen t a nd del iv ery of groundand spacecraft equipment and support ing documentat ion

Design and fabricat ion of specia l-pur pose tes t equipm ent and f ix tures

P r o c u r e m e n t of al l genera l -purpose tes t equipment

Con tro l of facil ity conf igura tion

Pre par at io n of E STP documents

Coordination of individual black-box testing and conducting necessarysubsys t em and sy s t em pe r fo rmance t e s t s i n a cco rdance with hard-wa re pe r fo rmance r equ i r emen t s

Obtaining data on TCSD and con tra cto r te sts of space craft a ndground-suppor t hardware tha t may be re la ted to the ESTP

Supplying system engineers to support compatibi l i ty and performanceevaluat ion tests

Sche dulin g of tests and re la ted ac t iv i t i es

Prepa ra t ion of t es t p lans , p roced ures , and repor t s

Providing all test predic t ions

Chair ing al l test planning, status review, and final review meetings

Direct ing tests and providing reduct ion, analysis , and disseminat ionof test data

Coordinating and expediting resolution of problem areas assoc ia ted

e i t he r with t e s t r e su l t s o r ava i l ab i l i t y of approp riate equipmen tf o r t e s t

Maintaining adequate systems documentation and expediting flow oftest da t a and r e su l t s t o app rop r i a t e u se r s

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TABLE I. - ELECTRONIC SYSTEMS TEST PROGRAM PARTICIPATION - Concluded

Responsibi l i t ies

Support ing spacecraft s ystem procu rement and assist ing ESTP inobtaining appropriate spacecraft contractor part icipat ion

Ass is t ing in the acquis i t ion of spacecraf t equipmen t document ation

Part icipat ing in the preparat ion of t est plan s of i n t e r e s t

Provid ing da ta for use in dynamics ests when requested

Part icipat ion in analyzing results of tests of intere st and conc ern

Spec ifica tion and p rocu reme nt of MSFN equipment

Direct ion o r sup erv isi on of t he installation and checkou t of M S F Nequipment in the ESTL

Prov id ing a s s i s t ance o r consultat ion during subsystems test ing andsys t ems t e s t s

Part icipat ion in overal l planning, test ing, and data evaluat ion

Supporting resolution of MS FN- relat ed proble m area s asso ciat edei the r with t es t re su l t s o r equipment avai labi l ity

Providing MSFN equipment op erator training

Updating MSFN equipment at ESTL in accordance with overall MSFNupdates and advis ing MSC perso nnel of forthcomin g changes thatmay impact or invalidate test r e su l t s

Providing data on GSFC- o r contractor-conducted tests that mayaffect the ESTP

Essent ia l ly the same as MSC/TCSD supp ort activit ies, but relatedto booster telecommunicat ions equipment

Essent ia l ly the same as, and in conjunc tion with, GSFCAdvising of any unique launch instru mentation syste m characteristics

requir ing compatibi l i ty and performance test ing

Monitoring test program to keep awa re of prob lems encou ntered an dsolut ions proposed

.. , ." ~~ ~~~

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PROG RAM CONCEPTS AND DEVELOPMENT

The primary object ive of the ESTP has been to provide a high level of as su ra nc etha t spacecraf t , ex t ravehicu la r? and M S F N t e lecommunica t ions sys tems a r e compatiblean d t ha t t he ove ra l l sy s t ems pe r fo rmance l eve l s re commen sura t e wi th pro jec t goa lsand indiv idual missi on requi remen ts . In th e pr oc es s of achievin g this object ive, sev-eral secondary object ives have been real ized. These object ives a r e the per formanceof tes t s ear ly enough pr ior to manned f l igh t to ass i s t in de te rmin ing overa l l sys temsdesign requirements and specif icat ions, recommendations for modif icat ions where in-compatibi l i t ies a re found to exist o r pe r fo rmance l eve l s a r e found to be insufficient,determinat ion of opera t iona l const raints , and recom menda tions for syste msimprovements .

To a t ta in these ob jec t ives , a t e s tconcept consist ing of fou r disc ret e lev elsof te st ef fo rt was devised. These levelswere chosen on the assumption that a l lcomponent qualification, as well a s sub-systems test ing and environmental qual if i -

performance

p r i m e con t r ac to r f a c i l i t i e s . The fou rca t ion , occurs a t the manufac tur ing o r

test ing levels (f ig. 1) a r e s u b s y s t e m s

sys tems compat ib i l i ty tes t s , and probleminvestigationvalua t ion tes t s , sys tems in tegra t ion tes t s ,

ing , "spec ia l t es t s , " is described in sub-reso lu t ion tes t s . A fifth categ ory of te st -

s e q u e n t p a r a g r a p h s .

Systems cornpatlbillty

total systemscompatlbllity and

evaluation

0Problem area

functlonal checkout

Systems ntegration

( ~ensd0oO1 an dalibration )

The subsys tems eva lua t ion tes t s a r e Subsystems evaluationsubsystems performance

( verification and updating)Adesigned to check each subsystem (or"black box") indiv idua lly to verif y per-formance according to speci.fication andto obtain important calibration data forfol lowing ests . These subsystems evalua-tionestsnotoesedithlifi- I groundquipment)ca t ion or acceptance tes t s ) have as t h e i rprimary objective hedocu menta tion of Figure 1 . - Tes t onc ept of the ESTP.i m p o r t a n t p a r a m e t e r s s u c h as bandwidth,dynamic range, power output, and stabilitywhich a r e required before compatibi l i ty test data can be properly ut i l ized. Spacecraftand ex t ravehicu la r subsys tems eva lua t ion tes t s a re per formed in TCSD l abo r a to r i e s a t

MSC. The M S F N and special-purpose test equipment subsystems evaluat ion tests a r econducted in the ESTL.

Subsystems romprlme contractor

lspacecraft and

The sy s t ems i n t eg ra t i on t e s t i ng (o r sys tems eva lua t ion tes t ing) is designed tover i fy proper opera t ion and in te rconnec t ion of the spacec raf t , ex t rav ehicu la r, orM S F N equipment; to obtain further cal ibrat ion data a s requi red ; and to ver i fy properin te rconnec t ion of the overa l l communica t ion s sys tem in prepara t ion for sys tems com-patibi l i ty tests . The ul t imate object ive, then, of the syste ms evalu at ion test is t oa r r i v e a t a fully configured ESTL tes t bed with which a pa rt ic ul ar se r i es of compatibil -i ty and performance evaluat ion tests can be performed.

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8. Television picture qual i ty

9. Keyed-carr ier code- copy accuracy

The four th leve l of test ing, the problem resolut ion tests , is conducted in morede ta i l but on res t r ic ted por t ions of th e overa l l sys tem to explo re prob lems de te c ted

during the systems compatibi l i ty tests . I t is thi s lev el of test ing, pr imari ly, whichenable s real iz at ion of the secon dary ESTP object i ves discus sed earlier. The problemreso lu t ion tes t s a r e often run concurrent ly with compatibi l i ty tests on s imula ted space -craft and groun d equipment ; only when a resolut ion is found a r e the ongoing compatibil-i ty tes t s in te r rup ted to ver i fy the so lu t ion on the opera t iona l equipment . Problemresolut ion test ing is also conducted when theoret ical analyses indicate potent ial prob-lems and when anomal ies a r e detected during a miss ion .

A s imi l a r bu t less direct ly related level of test ing, designated s imply a s spec ia lt e s t s , is perf orme d (upon requ est ) to develop system s mprovem ents n he case ofmargin al perfor mance, to verify new designs in the conceptual s tage of hardware de-velopment, o r t o see i f the ex is t ing sys tem can accommodate new in format io n t ransfero r rela y req uire men ts . This leve l of test ing also includ es verif ic at ion of cer tain NASAGoddard Space Flight Center (GSFC)-engineered modifications to the MSFN equipmentp r i o r t o release to all MSFN si tes , astron aut demonstrat io ns where voice-conf erencin gc ap a b i l i t i e s and p rocedu re t e s t s a r e conduc t ed w i th a s t r onau t pa r t i c i pa t i on , and igh-gain antenna tracking tests with varying up-l ink t ransmission modes. Special supportto the MCC als o is included here by incorp orat in g a te mp or ar y hookup to the MCC o rsimply by making appropriate tape recordings to be replayed in the MCC o r over theMSFN to th e MCC.

Both the problem reso lu t ion tes t s and the spec ia l t es t s , a s s epa ra t e c a t e go r i e s ,are rela t ive ly late dev elop ment s in the ESTP. It was found that to stop and reconfigurefor tes t ing covered by these ca tegories in the middle of , o r between, regularly sched-uled systems compatibi l i ty tests of ten jeopardized schedules to the point that data ei thercould not be made available in time to be useful (spacecraft development too advanced),or the data taken were no longer applicable because of systems changes. Theref ore,the separa te ca tegor ies were es tab l i shed , and tes t ing was scheduled dur ing off - sh i f tperi ods , on simulated equipment, or in se pa ra te la bo ra to ri es (the MSC Audio Tech-niques and Evaluation Labora tory and the MSC Communications Systems EngineeringLaboratory) organizat ional ly and electr ical ly connected with the ESTL. However, be-cau se of pr io ri t ie s o r possible consequences, the mainstream tests of ten have been de-layed s o tha t p roblem reso lu t ion tes t s o r spe c ia l t es t s took pr ior i ty. On each suchoccur rence , the tes t personnel worked c lose ly wi th the reques t ing organiza t ion and es -tab l i shed procedures and schedules acceptab le to all concerned. In many of these in-stances, however, the data analysis and f inal report ing have been lef t to the request ingorganizat ion so that other test ing may procee d. In essence, then, the original test ingconcept of the ESTP has been modified to provide flexible and rapid respon se to urgentrequirements that affect system design, requirement implementat ion, o r crew safe ty.Also , fu ture program suppor t , where s imple explora tory tes t ing can c la r i fy sys temscapabi l i t ies an d al low f i rming up of concepts , has been employed.

A f u r t he r r e f i nemen t i n t he o r i g ina l p l an of the ESTP occu rred rath er early inth e p r og ram. In many instan ces at that t ime, only early breadboard-type equipmentwas avai l able for tes t ing and only f o r a sho rt pe riod of t ime; the prototype o r opera-tional equipment on a more permanen t bas i s was no t ava i lab le un t i l severa l months

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later. Consequently, systems compatibility testing was divided into two typ es - r o s scompatibi l i ty test ing and detai led compatibi l i ty and performance evaluat ion test ing.The gross compat ib i l i ty tes t s were des igned to ob ta in maximum informat ion about theequipment in a s h o r t t i m e - sual ly 4 t o 6 weeks. Only two major conditions weretested: nominal parameter and range values and combin ed worst-case values. Thistesting allowed detection of major incompa tibil ities, but tended to bypass minor prob-lems. The detai led compatibi l i ty tests , which cover all expected conditions, comela te r and usua l ly las t 3 months ; Here , minor problems a r e fe r re ted ou t , spec ia ltes t ing is ins ert ed upon request , and complete documentat ion on the operat ional syst emis obtained.

Test techniques a re continually being developed for the ESTP. Such items a sspeech- to-noise ra t io measurement , f rame-synchroniza t ion loss - ra te measurement ,noise-f igure measurement , and others have been develop ed to yield greater accuracyand to reduce tes t t ime where poss ib le . A s tudy is now underway on ESTP accuraciesbased on measurement tolerances and interact ion s; the down-l ink telemetry channelpor tio n of th e stu dy is complete and the down-l ink normal voice channel port ion isnear ly s o .

Strict configuration control of the ESTL equipment used for the ESTP is main-tained. A detai led descrip t ion of the ESTL equipment . sample test plans, s ignal f low,and qual i ty and configurat ion control proced ures are contained in a five-volume reportprepared by MSC. A l l vo lu mes ar e updated periodically to ref lect changes in proce-du re s and equipment . Test program operat ions and ESTL equipment and support capa-b i li ty a r e um ma r iz ed in ppendixes A and B, respec t ive ly. S imi la r cont ro l ismaintained over the Audio Techniques and Evaluation Laboratory and the Communica-t ions Systems Engineering Laboratory whenever these laboratories perform tests d i -rect ly related to the ESTP. A brief descr ipt ion of labora tory capabil i t ies avai lable isgiven in appendix B. The original program plan and sequence of test in g, a s proposedin the five-volume report, have been adhered to except for two maj or cau ses . Onecause , t he l a rg e s t pe r t u rb ing f ac to r, w a s that addit ional tests (extravehicular astro-naut demons t ra t ion tes t s , rf t rac ker t es t s , Apol lo lunar sur face exper iments package(ALSEP) tests , Apollo range instrumented aircraf t (ARIA) perfo rmance evalu at ion tests ,etc .) were implemented and completed. The total t ime added by th i s cause w a s over1-1/2 years . The secon d cause (of less s ignif icance) was tha t increased tes t scope ,including special test ing, took more t ime than original ly forecast . The t ime increasefor the la t te r cause was approximate ly 6 months . The to ta l increase in t ime was, then,approximately 2 years. A s a re su lt of this additional testing, many significant contri-butions - mportant in design, in development, and ultimately in mission operations -were ma de by each of the previously l is ted program phases.

The ESTP has made the following significant contributions to the ACS. (Th enumbering sequence does not indicate relat ive s ignif icance.

1. Verif icat ion of overa l l syste ms compa tibi l i ty

2. D e te rmina t i on of ove ra l l sy s t ems pe r fo rm ance l eve l s and cap ab i l i t i e s

3 . Evaluation of im pa ct of inco mpati bilit ies and insuf ficie nt perfo rmanc e

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4. Verif icat ion of ana lyses and pred ic t ions

5. Derivat ion of information not read i ly ava i lab le from ana lysi s

6. Aid to all groups requir ing understanding and knowledge of sy st em sch a r a c t e r i s t i c s , pe r fo rmance l im i t a t i ons , and ope ra t i ona l cons t r a in t s

7. Aid to a ll groups in reso lv ing problems, es tab l i sh ing per formance spec i f ica-tions , and verif ying adequ acy of chang es

8. Verific ation of equip ment desig n in breadb oard stage

The ESTP has resu l ted in a comple te and thoro ugh docume ntatio n of the per-formanc e capabi l i t ies a nd the l im itat ion s of the ACS and can provi de s imila r resul t sf o r any communicat ions system used for manned space f l ight .

TESTACTIVITIES

Test in g act ivi t ies under the ESTP were begun in September 1964, in tempora ryf ac i l i t i e s a t MSC, an d have continued without nterruption, except or brief econ-figurations and update periods including elocation o he permanent acility), untilthepresen t ime . The pec i f ic es t s onducted a r e descr ibed n h i s ec t ion . Forconvenience an d emphas is , hey a r e grouped n to hree ca tegor ies : major es t s( to ta l spacecraf t /g round es t s ) , spec ia l es t s par t ia l spacecraf t /g round es t s ) , ands up po r t e s t s ( spec i a l pro ble ms of lesser manpower significance han he specialt e s t s ) . A schedule which l lustrates he ime equence and elatio nship of th es et e s t s is shown in figure 3. Signif icant outputs from the tests are discussed in the sec-tion entitled "Significant Results. I'

Figu re 3 . - Tes t activ ity of the ESTP from 1964 to 1969.

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Major Tests

Major tests (designated "A") are aimed at verifying overal l communicat ions sys-tems compatibi l i ty and performance for ove ral l program support and do not , a s such ,cover such special test ing as determining systems capabilities to fulfill individual mis-sion objectives where they differ from flight to flight. However, the major tests do

establish basic performance cri ter ia and capabil i ty and information from which specif icmission capabilities can be derived.

The f irs t two tests d escrib ed (A- 1 and A-2) were p erf orm ed a t MSC under con-tr ac t (NAS 9-2563) with a maj or sup pli er of spa cec raf t and MSFN equipment. Theequipment tested was not operatio nal because the spacecraft equipment was the CSMBlock I en gineering (Block I-E) model, o r production prototype equipment, and theMSFN USB RER system was actually a Deep Space Network system modified f o r Apollofrequencies. codes. and subcarriers . Sufficient ly good data were obtained, however,to confi rm the basic ac cepta bilit y of the Block I equipment and to affect significantlythe Block I1 design quite early in the design process. Also, sign ificant and valuableexperience was obtained whereby MSC perso nnel could effectiv ely carry on with the

test program after complet ion of the f i rs t two tes ts . These and other tests are dis-cussed in more detai l in the following paragraphs.

Command and service module Block I-E USB te st s ( A - 1). - The primary object ivesof t he CS M Block I-E USB te st se rie s wer e to ver if y the Block I ACS overall comp atibi l-ity and . to de termine . a s early as possible in the manufacturing and assembly stages.the performance that could be expected from the ACS. W h i l e final hardware configura-tions wer e not available until later (for A - 4 te st s) , t he CSM Block I-E equipment testedwas sufficiently similar (and in many ca ses iden tical) to the final Block I sys tem s o thatperfo rming the tests becam e worth while . The same can be said of the ground S-bandsystem, which was later converted to the Apollo configuration (frequencies, sub-c a r r i e r s , e t c . ) f rom a ,JPL configuratio n. Much of the effort expended on th is te st

serie s became direc tly appli cable to the Block I1 and lunar-configuration systems de-sign and testing which were to follow.

. . .. - - " . ". " .- - _. . . . . . ."

Two maj or class ifica tions of tests were accom plish ed. The f i rs t of thes e wa s todetermine the compatibi l i ty and performance of the overal l system. These tests de-ter mi ne d su ch ch ar ac te ri st ic s a s PCM data quality, voice intelligibility. updata link(UDL) quality. ranging accuracy , and acquisition time, all at various rf received signallevels and carr ie r thres holds . The secon d class if icat ion of tests included invest igat ionof problem areas detected in the comp atibi l i ty and performance tests and also in cludedT V demodulation tests, emergency-key demodulation tests, and low-frequency inciden-tal amplitude modulation (IAM) and incidental phase modulation (IPM) tests designed toanswer spec ia l ques t ions tha t a rose regard ing sp acecraf t (par t icu lar ly the lunar mod-

ule (LM)) high-gain antenna pointing accuracy and stability effects on data quality. Thiss e r ie s of tests prov ed the basi c compa tibili ty of the Block I ACS. However, a s notedpreviously, several problems that had to be solved prior to a lunar mission were un-cove red. At th e tim e of thes e te st s, th e Block I ACS wa s no longer intended for use atlunar dista nces; some of the problems detected, however, were common to both theBlock I and the Block I1 sys tem s. Othe r probl ems wer e not seriou s enough to demandmajor hard ware rewo rk but did require systems or operat ional constraints . Someproblenls indicated the need for detailed specifications, primarily in regard to systems

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pe r f o rmances and i n t e r f ace s . The ma jo r p rob l ems i n e ac h ca t ego ry a r e presented intable 11. Based on resu l t s of t h i s t e s t se r ies , the proble ms were cor rec ted by hard-ware, documentat ion. or procedure changes. In many ins tances , fu r ther t es t ing w a sneeded prior to making any defini te correct ions to the problems. Some of the addi-t iona l t es t ing per formed is discussed in la te r sec t ions of t h i s repo r t .

TABLE 11. - BLOCK I-E P ROBLEM AREAS

Problem Resolut ion

Problems requi r ing reso lu t ion pr ior to lunar miss ions

~~ ~ . . - . iL .~_

Transponder no ise- f igure degrada t ionof 6 dB in the high-power mode wascaused by th e p as sa ge of the S-band

travel ing-wave-tube-generatedC-band noise through both the trans-mit and the rec eiv e arm of thed ip lexer.

When the t ranspo nder was in the rangingmode, up-link data were turnedaround and remodulated onto thedown link, severel y degr ading the51.2-kbps telemetry data.

Incor rec t range ta l ly read-outs for cer-tain range-code delays were causedby de si gn er ro r in the rangingsubsys tem.

Downvoice distortion was cause d by amismatch between the voice demodu-lator and the output amplif ier.

Quality of upda ta did not corres pond topredict ions a s a re su lt of poor detec -tor des ign .

400-Hz power to the t ransponder con-tai ned AM as a re su lt of load changes:this condit ion caused undesired PMon the down l ink, which degraded re-ceived data.

Block I - low-pass f i i t e r was in -s e r t ed i n t he t r an smi t l eg of the poweramp l i f i e r.

Block I1 -- N o problem was expectedbe ca us e of the presence of a p r e -s e l ec t o r in t he r ansponde r e -ce iver and a low-pass i l ter n het ransmi t Arm.

Block I - he up-link modulation indiceswere reduced.

Block I1 - he problem was minimizedby transp onde r desig n.

P e r s o n n e l a t J P L c o r r e c t e d t h e p r o b l e m .

Person nel a t GSFC cor rec ted the problem.

Block I - he quality was adequate.

Block I1 - des ign cor rec t ion wasincorpora ted .

Block I - much improved inverter wasdesigned by the con tracto r.

Block I1 - he transponder design in-cluded dc regulat ion.

- ~ - _ _ ~ -"

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TABLE 11. - BLOCK I-E PROBLE M AREAS - Continued

~ . . . ~ .~ - . ~~ -~ . . .

ProblemI _ _ .

Resolution. . . - . - " - .~ ~ ~ ~~

Problems requi r ing sys tem cons t ra in ts". . ~~ ~- ~ . . .. . .. . . . "

In certain op erati onal m odes of the CMand the LM, the received LM down-link signal strength could be consid-erabl y stron ger tha n that of t he CM.This situa tion would d egr ade CM down-link data quality.

Very weak up-link signals caused noisemodulation on the transponder voltage-

controlled oscillator (VCO).

Energizing and deenergizing up-linkmodulation during range-code acquisi-t ion caused the ranging subsystem tor e s e t .

Design of the audio cen ter was such thatupvoice was fed back into the down-voice channel, thereby limiting maxi-mum obtainable voice intelligibility.

During PCM 1: 1 data-playback modetests , data quali ty was degraded ap-proximately 1 dB a s a re su lt of re -co rde r ha rac t e r i s t i c s . Th e32: 1 playback performance w a s nottested because required equipment wasunavailable.

-~"

~. - - - . -" -~ . ~~"

Tests to de termine the maximum s ignaldifferential for acceptable data qualitywere per formed, and the resu l t s wereforwarded to appropriate missionplanning groups.

Tes ts to de termine the poin t a t whichthis condition affects PCM data quality

were per formed.

These functions cannot be changed duringrange-code acquisition.

Block I1 specific ation s were changed toimprove this condition.

Degrada tion of 1 dB was cons ideredacceptable.

Problems requir ing specif icat ion requirements- _ _ _ ~~~ .. .. . . - " -~ ~ " .

Detected UDL subbits cou ld be invertedif one of many inter face s was not

properly interfaced.

Inversion of t he TV pictu re cou ld occ ur,depending on the amplification used atthe ground." "" -~ " . . ~~ "". ~~

Po1arit.y at ea ch point in the system hadto be specified and closely observed.

The number of am plifi catio n stage s or aninver ter at the TV monitor input ( o rboth) had to be specified.

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.

TABLE 11. - BLOCK I-E PROBL EM AREAS - Concluded

Prob l em I Resolution~~~ ~

Problems requi r ing spec i f ica t ion requi rements - ConcludedReal- t ime PCM subcarr ier modulat ion

was such tha t p roper f rame synchroni -zation could not o ccu r.

Long st ri ng s of ' ( 's ' ' o r "O1s" in thePCM data stream could possibly causeloss of lock by th e bit -ra te clock onthe ground.

I~~ ~~.. - "" -~ .~

The decommutator specif icat ion had toinclude p rovision for operat ion on bothda ta and da ta complement ( inver tedb i t s t r e am) .

The PCM bit and word formats h ad to bespecif ied in such a manne r that longse r ies of " 1's" o r ''O1s" wer e notpresen t in the format .

Command and service module Block I1 ( s imula ted) compat ib i l i ty tes t s ( A - 2 ) . - Thepri mar y obj ect ive of th e CSM Block I1 ( s j .mula tea compat ib i l i ty tes t se r ies was t o ve r-i f y the compa tib ili ty and perfo rma nce of the intended CSM Block I1 design by using sim-ulated CSM communicat ions equipment and operat ional ground equipment . (The groundUSB system used for the Bloc k I-E t es t s w as rep lac ed with an opera t iona l sys tem spe-cifically designed for the Apollo Program. ) The subca r r i e r demodu la to r s we re s i mu -lated; that is , the y wer e not the planned operational units. Simulated CSM equipmenthad to be used because the Block I1 design had not been finalized. The Block I1 equip-ment was simulate d by the Block I "E-5" t ransponder modif ied for Block I1 p a r a m e t e r sand by a "Universal" (or adjustable) spacecraft communicat ions system which was pro-

v ided for th i s t es t and is now ass igned to the probl em reso lu t io n phas e of t he ES TP .Consequently. this test ser ies a l s o s e r v e d as a des ign ver i f ica t ion tes t fo r the CSMBlock I1 c ommun ica t i ons sy s t em. Fu r the rmore , p rob l em a reas could be resolvedmore read i ly s ince the des ign was not f i rm .

. . " " - ~ . . . . . ~

The types of t es t s p er form ed were very s i mi la r to those d one for the Block I-Emode l (A-l), exce pt that some missio n profi le tests , in which a dynamic Doppler sim-ulator was used to s imulate spacecraft veloci ty and range chan ges, were performed.Also, the number of data points taken for each channel was somewhat reduced becauseof the l imit ed t ime avai lab le.

Again , the test serie s verif ied the basic comp atibil ity of the communications s y s -tem design, this t ime for Block 11. Also, as before , some problems were uncoveredwhich had to be resolved. These problems can be categ orized as before, an d the majoro nes a r e p r e sen t ed i n t ab l e ID. A l l neces sa ry co r r ec t i ve ac t i on h a s been taken. Thisact ion has occurred. however, of ten a s a re su lt of furth er tes tin g, som e of which isdescr ibed in later sect i ons of thi s rep ort .

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TABLE 111. - BLOCK 11 SIMULATED SYSTEM PROBLEM AREAS

~~~~.. _ _

P r o b l e m I ResolutionProb l ems r equ i r i ng r e so lu t i on p r i o r t o l una r m i s s ions

". . ..

-. ". - =. . - " . . . . - - - ~For low spacecraf t t ransmi t power and

omnidirectional antenna configura-tion, the total ground-received signalpower f rom lunar d i s tance was 1 .8 dBbelow that required for 80-percentcopying ac cu ra cy of key ed tone s.

Difficulty in acquiring both the up linkand the down link was experienced.This w as cau sed by frequency"pushing" effects and spurs gener-a ted by in te rmodu la t ion p roces sesbetween the signal and VCO.

- . .~ ~ . ~ . . " -

GSFC personnel redes igned the f i l t e r-demodulator subsystem for detect ionof eme rge ncy key .

Hardware changes were ach ieved bychanging f i l ters a ssociated with boththe t ransponder a nd MSFN phase-lockloops.

P rob l ems r equ i r i ng sy s t em cons t r a in t s- . - . ~ ~ "~ . .

Plus-Doppler offsets caused slight deg-rad ati on of vo ice and UDL chann elperformance; negat ive offsets causedimprovement of s imilar magnit ude.This was caused b y phase sh i f t s re-su l t i n g f rom t he t r an sponde r c a r r i e rloop s ta t ic -phase e r ror and was mos tnoticeable at weak signal levels.

Tel eme try BER using the DSE w a s some-what degra ded for the real- t ime case.Also, f o r 3 2 : 1 playback, the best

BER achievable was 1 X 10- '.Carr ie r-acquis i t ion d i ff icu l t ies a l so

caused operat ional constraints .

The problem is a function of r at e andmagnitude of Dopp ler and must beaccounted for in c i rcu i t marg incalculat ions.

The problem must be accounted fo r inc i rcu i t marg in ca lcu la t ions .

Prohibi t ion of a l l up-link modulationdu r ing ca r r i e r a c qu i s i t i on was oundn e c e s s a r y,

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Command and service modu le Block I-D/MSFN USB compatibility tests (A-4). -The CSM. Block -1-D. model USB- equip ment and h e MSFN .RER-Kbsystemswent intote st in g n ea r t he fi rs t of May 1966, and the testing was concluded in mid-June 1966.The r esult s of the tests were compared to the system specif icat ions and to expe ctedperformance. This compariso n indicated that audio center crosstalk and the presenceof excessive noise in the crewmemb ers ' headsets (when the crew audio sw itch was on

with the 30-kilohertz up-link subcarrier off) creat ed prob lems. Also , the resul ts ofantenna switching indicated that the automatic switch affected the USB equipmentcarr ier-acquisi t ion threshold and that condit ions existed in which the antenna switchcould go into oscillation. This automatic switch was not incorporated into the finalBlock I1 design.

Th e re su lt s of incidental modulation tests indicated that 2-percent amplitudemodulation (AM) of the 400- hertz spa cecr aft equip ment pow er at a 35-hertz ratecaused IPM of the S-band carrier. This condition affected data and acquisition. Themaximum measured effect was approximately 5 decibels on acquisition of t he ca rr ie rby the USB equipment. This effect occurred for 50" peak IPM at frequencies above200 hertz. The data degradation, n general , was approximately 1 decibel. These

r e s u l t s , as they pertain to the effect of IPM on the down link a r e , of c our se. app lic abl eto a l l so ur ce s of IPM that appear on the down link. (Another source is high-gain an-tenna vibrations. )

Severa l problems d iscovered dur ing the Block I -E tes t s we re s t i l l p r esent . Manyof the problems and their solut io ns are l is ted in table V . Seve ral problems, thoughfi rs t noted on Block I, were applicable to Block I1 als o.

TABLE v . - COMMAND AND SERVI CE MODULE BLOCK I/MSFN

USB PROBLEM AREAS

~ ".i - ~ - ~ - ~ . -. " - . ~"Problem

- . . ." ." . - . . . . L . ".Degradat ion of PCM te le me tr y was

ca us ed by turn aro und of up-linkchannels .

System degrada tion was caused by poorreg ula tio n of the 400-Hz power supply,causing AM and PM in the modulator,the VCO, and the power amplifier.

Deg radat ion of UDL at low sig nal le vel swas cause d by degraded up-linksignal- to- noise ratios.

-~ -. . - . ."

~~ . "r". . .

II___ -

Resolution

Block I - plink modulation indiceswere reduced.

Block I1 - ransponder TAR wasreduced.

F o r both Block I and Block 11, a muchimproved inverter system (effect iveon Apollo-Saturn 202) wa s de si gn ed bythe contractor. Block I1 sys t ems a l sohave regulated dc power supply.

For Block 11, an improved diode-typewideband phase detector wasimplemented.

. . .

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TABLE V. - COMMAND AND SERVICE MODULE BLOCK I/MSFN

USB PROBLEM AREAS - Concluded

P r o b l e m

Degradation of the t ransp ond er (rece ive r)noise f igure was caused by spur iousoutputs of the power amplif ier.

The signal margin was inadequate for theemergency key (assuming fa i lu re ofthe power amplifiers and the high-gain antenna).

Degr adati on of UDL w as c au se d by IAMof th e gro und SCO.

A fa l se lock occur red .

Transponder dynamic t racking- looppa ram et ers wer e not compat ib le wi thoperational acquisition and loop track-ing requi rements .

Data s igna l po la r i t i es were reversed(PCM, UDL, T V , and PRN).

Degradation of PCM te le me tr y wascause d by IPM in the spacecrafts y s t em .

" . -. - ~ . - -~

Resolution- ~ - . . - . . . . -

A low- pas s f i l te r fo r Block I and a p r e -se le ct or fo r Block I1 were imple mentedby the cont ra c tor.

Perso nnel a t GSFC redes igned the f i l t e r-demodula tor sys tem to ach ieve ac-ceptab le per formance .

Reduced up- link modulation indices mini-mized th i s e ffec t . Personnel a t GSFCiniti ated deve lopme nt of impro ved SCO.

Opera t iona l p rocedures were devised tominimi ze the poss ibilit y of MSFN fa ls elock. Also, spacecraft and MSFN fi l-t e r s we re r edes igned .

New t rack i ng- loo p paramet ers (ga in ?bandwidth, an d al lowable s tat ic-phase

e r ro r ) we re spec i f i ed fo r B lock 11.Slower MSFN exc i te r sweep ra tes wer especif ied for Block I acquisi t ionp rocedu re s .

Tota l sys tem polar i t i es were spec i f ied toall conce rned; some MSFN hardwa rewir ing changes were a l so requi red .

The specif icat ion to the s pacecraft con-t rac tors was changed to l imi t to ta l s y s -t em IPM to 28" rms (less than 2-dB

te lemet ry degrada t ion) .- - "~

Command and service module Block II/MSFN USB gross comp ati bil ity test s~ ~- . ~ . . . - " - - ." . " .. . ~ ""

A-5). - The C S M communications equipment, including the USB equipmen t and theMSFN RER subsystems, entered test ing in mid-June 1966, and the tests were com-pleted in mid-July 1966. These tests were perfo rmed to deter mine whethe r any prob-l em de t ec t ed du r ing t he ea r l i e r t e s t s ( A - 2 ) remained in the prototype equipment. Thet e s t r e su l t s r evea l ed two ma jo r p rob l ems . F i r s t , t h e spec i f i ed b i t e r ro r r a t e (BER)

of 1 x could not be achie ved when the MSFN rec eiv er was uned t o the 700-hertz

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loop bandwidth, and the backup voice was phase modulated on the car r ie r with 1. 6-kbpstelemetry imposed on a 1.02 4-meg aher tz subc arrie r. The spec if ied BER could beachieved when the receiver was tuned to the 50-hertz loop bandwidth.

Secondly, when the up-l ink carr ier was phase modulated with the pseudorandomnoise (PRN) range cod e at 1.34 radians, the power in the received ran ge code at theMSFN site was s o strong that the correct ranging procedure could not be followed un-

less additional atten uation was incor porated into the MSFN rang ing r ecei ver d esign .The available at tenuation in the ranging receiver was 12 deci bels , and te st resu l ts in-dicated that an additional 5-decibel attenuation was required. Thes e problems aresummarized in table VI.

TABLE V I. - COMMAND AND SERVICE MODULE BLOCK II/MSFN USB

GROSS TEST PROBLEM AREAS

Problem

Block I1 PCM performance w a s degradedin the back-up voice mo de with theMSFN receive r tuned t o the 700-Hzloop bandwidth.

Block I1 PRN performance (dynamicrang e of MSFN rec eiv er to acc omm o-date wide variation in PRN modulationindex) was inadequate.

Resolution

The specif ied BER could only be achievedwhen the 50-Hz receiver loop w a sused.

An additional 5 dB of attenuat ion was in-corporated in the ranging receiver,and new up-link modula tion indices forranging modes were specified. Also,M G C capabil i ty was added for theMSFN rec eiv er.

- unar module/MSFN USB gros s comp atib ility t ests (A -6). - The LM/MSFN USBtes ts began in mid-October 1966, and were completed during the f irs t week of Decem-be r 1966. The tests were necessary to verify that the LM transceiv er and the MSFNRER subsystems were comp atible with the system specification and with mission re-qui rements . Per formance charac ter i s t ics such a s BER, probability of c o r r e c t a c -quisition, range-code acquisition time, TV picture quality, and voice quality wereobserved and recorded. Several major anomalies were observed. These problemsa r e summarized in table VII. Many of the listed reco mmen datio ns resu lted in furt her

te st s, so me of which a r e discussed later in this report .

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TABLE VII. - LUNAR MODULE/MSFN USB GROSS TEST PROBLE M AREAS

P r o b l e m

Down-link voice quality (gross W I) t e s t sindicated ser ious deficiency in themaximum downvoice intelligibilityobtainable when space-suit noise wass imula ted . Suspec ted causes wereaudio center automatic volume controlamplif ier s tages emphasizing the in-put noise and high clipping levels inthe backup voice mode ( 2 4 dBspecif ied) .

The ranging modulation index of 1. 34 ra-dians requi red an i . f . attenuation of16 dB in the MSFN range receiver.The exist ing systems capabil i ty wasa ma xi mu m of 12 dB.

False lock occur red in the t ransce iverunder s t rong s igna l condi t ions( g r e a t e r t h a n -70 dBm) fo rAf = 90 kHz and df = 36 kHz/sec ,where Af is th e ra ng e of frequenc ychange and df is the ra t e of f re-quency change. A suspe cted causewas pushing effects as a re su lt of themult iple pole predetect ion f i l ter in theca r r i e r t r a ck i ng l oop .

Backup voice mode (signal combination 4)degraded PCM te lemet ry per formance(1.6 kbps) . The maxim um BER capa-bility when using the MSFN/RER50-Hz carr ier loop bandwidth was

4 x F orhe 700-Hz ca r r ie rloop bandwidth, the maximum BER

capability as 1 X A possi blecau se was i n t e r f e r ence as a res ul t ofcl ipped voice spectrum.

A 28" r m s IPM of ba ndlimited noise300 to 800 Hz had a significant effecton the PCM BER (approximately 5-dB

degrada t ion t 1 X BER).

2 0

Resolution

Sel ect ed re des ign of t he LM voice channewas accompl i shed to improve t imeconstants and l inear dynamic range.

Attenuation in the MSFN range rec eiv er

wa s nc re as ed . New up-link modula-t ion indices for PRN ranging modeswere spec i f ied . Al so , MGC capabilityin the MSFN receiver wa s added .

The f i l t e r was r edes igned .

Fur ther inves t iga t ion is continuing(presen t ly an opera t iona l cons t ra in t ) .

4 28" rms l im i t f o r IPM wa s spec i f i e d t othe cont rac tor.

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communications. Also, voice conference was not possible i f ei ther extravehicular as -t ronaut t ransmit ted E M U data, because this condition prohibited the other extravehicu-la r as t ronaut f rom '?breaking n . ' '

The E M U data channels performed sat isfactori ly, providing that the L M TV de-viation did not exceed f . 5 mega hert z. With out the tran smis sion of EMU data, voice"break-in" was possible under careful procedure control . However, the demonstra-

tion was troubled by heterodyning and, as expected, by rec eiv er ton es cause d by in-terac tion wi th the str onge r of the two-extravehicular-astronaut igna ls .

The tes t s and the demonst ra t ion proved tha t the CS could not support the newtwo-extravehicular-astronaut requirement. Because this was a major problem, equip-ment redesign and modification were initiated. (See description of t es t B-6. ) Thi seffort led t o the implem entation of a voic e subc arrie r sque lch for the LM S-band equip-ment and to the development of the extravehicu lar communication s system (EVCS) toreplace th e SSC.

Apollo com munications s ystem phase I1 compatibility tests (A-9). - The ACSphase If{.e%trav-ehiciEr astronadTBiock-II CSMTMFFNFtests w ere performed during

the period from Marc h to Sept embe r 1967. The purposes of the tests were to inves t i-gate in more detai l the perfor manc e of the extravehicular astronaut/C SM/MSFN portionof th e ACS test ed in pha se I and, in part icular, to invest igate possible operat ionalmodes to be used during the Apollo 9 mission. Updata and upvoice channel performancewas found to be slightly better than indicated by I nterface Control Docume nt (ICD) cir-cui t mar gin s for most mode s of operation. The command module (CM)-to-extravehicular-astronaut vhf voice channel was found to have considerable distortion:but WI was, neve rthel ess, close to the speci f ied 90-p erce nt leve l . Down-link telem-etry channel performance w a s a s pred icted , but only aft er a premodulat ion processorproblem w a s identified. The problem was a re su lt of an inherent biphase modulatio nproc ess fo r the high bit rate (51.2 kbps) showing up as a decrease in modulation indexfrom the specified value whenever 51.2-kbps modulation of n orma l tran sitio n density

was appl ied to the subcar r ie r. This appeared to be a gen era l CM prob lem. not limitedto the unit tested. D own-link phase modulation ( P M ) channel performance was accept-able . No pro ble ms wer e noted on the frequency modulation (FM) down link f o r 1: 1 tapeplayback: but the 32: 1 playback mode performan ce was. as in previous tests , less thandes ira ble for both voice and telemetry. It wa s found that the 95-kilohertz scientificdat a s ubc arr ier wa s p res ent within the transmit ted spe ctrum of the 32: 1 playback voice:as a r e su l t , a 64-kilohertz postdetect ion f i l ter was instal led on th e MSFN system toclear up this problem. The extravehicula r astronaut/CM/MSFN voice relay perform-anc e was good, although a high leve l of between-w ord interference was hear d as a r e -su l t of ex t ravehicular as t ronaut /b iom edica l da ta car r ie r in te r fe rence . (See descr ip t ionof t e s t s B-7 and C-19. ) The extravehicular astronaut/CM relay of biomedical data wassat isfactory. Television channel performance was acceptable, as was ranging channelperf orma nce. Test s incl uded inve stiga tion of modified (reduced) modulation indicesfo r up -li nk sub ca r r i e r s as wel l a s of specified indices. These reduced indices resultedf rom a t t emp t s t o r educe rf t racker problems d iscussed e l sewhere in th i s repor t andwere tes ted here to d e term ine the i r e ffec ts on channel per formance . The reduced in-dic es we re found to be compatible with circui t margin requirements for the perform-ance of the up-link channels.

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Command and service module/ARIA. _ . compatibility - e s t s- - A- 10). - Th e CSM/ARIAcommunicat ions compatibi l i ty and performance evaluat ion tests were performed inFebru ary and March 1968. Tests were perfor med joint ly by repr ese nta t ive s of MSC,U. S. Ai r Force Eas te rn Tes t Range (ETR) , and GSFC, us ing an ARIA a i rc r a f t on theground at El l ington Air Force Base connected to CM and simulated S-IVB communica-t ions equipment se t up in temporary quar te rs ad jacent to the a i rc ra f t . The purposes oft h e s e t e s t s w e r e t o v e r i f y ARIA/CSM USB com pat ibi lity an d to evalu ate the pe rfo rman celev els and cir cui t mar gin s fo r th e CSM/ARIA USB communic at ions sy stem prio r toscheduled ARIA mission support . This test program also inclu ded tests to determineS-IVB/ARIA tel em etr y link per form anc e and to det erm ine if any interference betweenthe S-IVB and CSM occ urr ed at the ARIA rec eiv er. The test pro gra m con sis ted ofvoice tests (ARIA-to-CM and CM-to-ARIA), telemetry tests (CM-to-ARIA and S-IVB-to-ARIA), and data-dump tests (recorded down-link information relayed to the MSFNfr om t he ARIA after complet ion of ac t iv e spa cec raft c ove rag e) .

In genera l , the tes t resu l t s ver i f ied tha t sys tems compat ib i l i ty and per formancewere commen sura te wi th miss ion communica t ions suppor t requi rements . Dur ing da ta -dump tes t s , however, the recons t ruc ted PCM data f rom the ARIA reco rde r weresever ely degra ded when receiv ed at the MSFN. A different modulation technique, usinga s ub c a r r i e r ava i l ab l e f r om the t ape r eco rde r, improved t he qua l i t y and was subse-quently adopted. Other minor problems, such as phase-lock loop instability caused byARIA rece ive r cry sta l oven on-off cycl in g, were also resolved.

Apollo communicat ions system phase 11 compatibility. _ _ es t s (A- 11). - Th e ACSphase I l l t es t s were des igned to es tab l i sh exper imenta l ly the ac tua l per formance l imi -tations and the communications quality of the oper ati ona l LM communications linksprior to the f i rs t manned lunar landing mission. Included in these object ives was de -sign verific ation of the redesign ed (tests A-8 and B-6) EVCS production equipmentinsofar as the equipment was part of the LM commu nicat io ns l ink. Primar y intere stwas in the voice channel performance between the LM and MSFN, and in the relay

modes with the EVCS.

The original schedule cal led for test ini t ia t ion in December 1968 (cal ib rat iontests) and comple tion of a ll t es t s by Ju ly 1969. Severa l o ther pr ior i t y tes t s assoc ia tedwith the Apollo 11 an d 1 2 mission s. howeve r, caused the sched ule for the phase I11test ser ies to be extended through December 1969. These priori ty tests are discussedin la te r paragraphs . Al l miss ion c r i t i ca l modes were never the less tes ted pr ior to theApollo 10 miss ion .

The phase I11 test ser ie s was divided in to eight segm ents cons ist ing of cal ibr at ionte st s ; UDL tests : PCM teleme try tests ; voice perfor mance tests ; an EVCS electr o-cardio gram (EKG), EVCS pulse amplitude modulation (PAM), and LM har dli ne (H . L. )biomedica l t es t s ; TV tes t s ; a ranging tes t : and r f -acquis i t ion tes t s . Ca l ibra t ion tes t sa r e a continuing item, a port io n being perfor med for each segmen t . The UDL, PCMtelemet ry, vo ice per formance , ranging , r f -acquis i t ion , and EVCS PAM tests a r e com-ple te . Te lev i s ion tes t s a re comple t e , based on the new color TV sys tem for the LM.The UDL tes t s , run f ro m Dece mbe r 16, 1968, to Ja nu ary 10, 1969, showed hat he LMUDL sys tem per formed wi th in spec i f ica t ions and tha t per formance was comparable tothe Block I1 CM UDL sys tem . Spe cia l inv est iga tio n of the backup upvoice, however,r e vea l ed some p rob l ems t ha t we re r e l a t ed t o t he LM commander microphone and side-tone circui try in the LM signal-proce ssor assembly (SPA). The voice output level from

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the 10-ki lohertz channel was too low; therefore, the s ignal was routed through the LMcommander 's microphone amplif ier. This rout ing caused the backup upvoice to beturned around and transmit ted on the LM down-l ink wave channel , producing an echoeffect at MCC. Opera t iona l and hardware so lu t ions were explored and severa l werefound acceptable; because of the del ivery and launch schedules, however, operat ionalso lu t ions (ground and spacecraf t opera tor p rocedures) were recommended .

The te lemet ry tes t s were in i t i a ted on Janua ry 17, 1969, and , a f te r severa l p r i -or i ty test in te r rup t ions , were comple ted on Feb rua ry 29, 1969. Results showed posi-t i ve c i r c u i t ma rg in s i n al l cases except the baseband modes. Tests also showed thatt he LM t e l e me t ry subca r r i e r amp l i t ude is reduced somewhat (8 percent) when modulatedby the high-bit-rate data when it had a ''1-0" t ransi t ion densi ty; this in turn affect s thecar r ie r modulat ion index and degrades overal l performance by approxima tely 0.5 deci-bel. Other activity is a imed a t co r r ec t i ng t he se p rob l ems .

Voice pe rforma nce test s were begun on March 5 and were completed in mid-March 1969. Upvoice test resul ts indic ated posi t ive lunar -dista nce perfo rmanc e mar-g in s f o r a l l voice u p-l ink comb inat ions fo r the omnidirect ional antenna and the MSFN85-foot-diameter antenna ; however, onboard squelch operated at a total received power

that was 7 to 10 de c ibe ls s t ron ger than the wors t -case spec i f ied to ta l rece ived power.indicating the possibility of pr em at ur e loss of up-li nk voice under certain condit ions.The squel ch circu i t can be switch deact ivate d, howev er. Down-link test resul t s showe dnegat ive per formance marg ins w i t h the LM s teerab le an tenna for cer ta in s ig na l combi-nations. The down-link relay voice test showed good per for man ce for a l l mo de s of in-te re st . Th e EVCS receiver tests showed good perfo rmance excep t for the case ofEVCS- 1 to EVCS-2 where only 70 percent W 1 was noted, quite possibly caused byEVCS-1 sub car r ie r in t e r fe ren ce . The vhf s igna l rece ived a t the LM was sa t i s f ac tory .

Down-l ink emergency-key tests also run at this t ime indicated sat isfactory per-forman ce for this commu nicat i ons mode. A 15-decibel discrepancy between prediciedand mea sured AM-key demodulator predetect ion signal- to-noise rat io was observed.

Invest igat ion indicated that spurious resp onse in the predetect ion f i l ter. coupled witha larger than specif ied noise bandwidth. raised the effect ive predetect ion noise power.

Th e EVCS EKG, EVCS PAM, and LM H . L. biomedica l t es t s were per formedfrom Apr i l 1 to June 6, 1969. Results using f l ight- type hardware showed that systempe r fo r man ce was s a t i s f ac to ry and t ha t a l l wo r s t - ca se pe r fo rmance marg in s we reposi t ive exce pt for cert ain insta nces whe re the EKG and PAM a r e on down-link signalcombination 10 with the LM steerable antenna and MSFN 85-foot-diameter antenna inuse; these negat ive margin s can be overc ome, howev er, by us e of the erectable an-tenna or the MSFN 210-foot-diameter antenna.

Becau se of th e chang e to color TV equipment, TV te st s a r e discussed in the fol-

lowing section as se pa ra te te s t s , no t par t of the p lanned phase 111 t e s t s e r i e s . Ra d i o -frequency-acquisi t io n and ranging test resul ts a r e still being evaluated.

Specia lTests

The major spec ia l t es t s (des igna ted "BfV) re a imed a t ver i fy ing par t icu la rchannel compatibility and performance; at resolving r ea l o r potent ial major problems

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,

detec ted dur ing the major tes t s , f l igh ts , o r ana ly se s ; o r at providing data o r p e r f o r m -ance demonstr at ion s to appropriat e person nel for purpo ses of just i fying changes, ob-taining systems configurat ion approval , o r i l lust rat ing effec ts of special equipment andcondit ions. These tests a r e discussed in chronological order in the fol lowingpa rag r a phs .

Additional S-band tests (B- 1). - The spacecraft equipment that underwent the ini-t ia l Block I te st s (s er ie s A-1) entered roughly 5 weeks of addit ional test ing in Septem-be r 1965 . The pr imary purpo se of these tes t s was to inves t iga te severa l ques t i onsident if ied fro m the resul ts of the Block I-E USB tests and from spec if ic anal yt icalst ud ie s pe rf or me d by the MSC Communications System Analysis Branch. In gen era l,the equipment used during these tests was the Block I -E spacecraf t sys tem an d an up-dated M S F N RER sys t em ( s e r i a l numbe r 1 4 ) . In some ins tances , the modi f ied E-5transponder which simulated a Block I1 unit (and which was used in the s imula tedBlock I1 tests , A-2) and three different 70-ki lohertz UDL di scr imin ato rs were use d.The specif ic quest ions which were to be answered by thes e tes ts , and the res ul ts oft h e se t e s t s , a r e summar i zed i n t ab l e VIII.

TABLE VIII. - ADDITIONAL S-BAND TESTS

Te s t-

UDL

Purpose

Determ ine the cause of degradedper for man ce by invest igat ingre la t ive phase sh i f t and 70-kHzd i s c r im ina to r F M improvement .

Investigate slope difference inS-band and baseband BERc u r v e s ,

1

"

- _ . - - - --

Resul t s__

I. - _ ." . "-

Apparent degradation in the UDLper fo rmance was found to be are su lt of degraded signal-to-noise rat io in the UDL disc rimi -na tor. The cause was notidentified. but areas for poss i -ble future investigation wereidentified. Relative phase shiftshould be held to less than ? 10"of the 1-kHz one. Larger phaseshif ts (25" to 30") did not appearto degrade performance morethan 0. 5 dB, poss ibly as a r e -su lt of the impulsive-type noisefound in the discriminator out-pu t . (P r ev ious d i r ec t e s t s u se d

a Gauss ian no ise source . )This pr oblem wa s found to be re -

lated direct ly to the s ignal- to-noise ra t io d i sc repancy d iscussedpreviously.

.. - " . .- ." ~ ""

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TABLE VIII. - ADDITIONAL S-BAND TESTS - Continued

Te s t

UDL

. ".

PCM

" .Upv oic e

"Purpose

Perform S-band tests with worst-case and best-case IAM up-linksubcar r ie r osc i l la tors , us ing aGSFC- supplied 5-percent AM

-"~

_ _ _ _ . ~ . .

70-kHz SCO.

Determine PC M performanc e byusing predicted down-l ink signallevels as a function of up-linksignal level.

Determine the PCM degradationcaus ed by turnaround up-linkmodulation by using reducedBlock I up-link modulation in-d ices for maximum and mini -mu m va lu es of TAR.

. .. .

Determine if upvoice intelligibilitycould be improved by using pre-

emphasis and cl ipping: and de-ter min e the amo unt of clippingdesi red. usin g orig inal Block Imodulation indices.

-~ .. _. "Resul t s

The effe ct of high IAM on li nk per -formance was noticeable. Lowermodulation ndices, however,minimized the problem forBlock I.

"" - - ~ ..

~- ." . ~

Ef fec ts of weak up link were notobserved when a constant 28-dBdifference was maintained be-tween up- link and down-linkrf levels , because the PCMchannel th reshold occurred be-fore the up- l ink car r ie r loopth reshold .

The PCM degradation was causedby tu rn ar ou nd of up-link modula -tion, using Block I turnaroundrat ios between 0. 5 to 1. 5 dB.This was considered signif icantif a marginal operational modewas to b e us ed f or Block I.

_" ~ -

A 2-dB improvement for 90-percentW I was ob t a ined , a t c a r r i e rthreshold, with 1 2 dB of cl ipping.Clipping of m or e th an 1 2 dB didnot increase improvement. andthe 2-dB improveme nt was notconsidered significant f o r plannedoperat ional modes. However,clipping did allow more consis-ten t sett ing of the upvoice modu-lation ndex. During ests, twas observed that the Block Iaud io c ent er AGC action degradedsign al-t o-no ise ratio by about

5 dB at the 90-percent intel l igi-bility evel. This should be con-s idered in c i rcu i t margincalculat ions.

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I1

TAB LE VIII. - ADDITIONAL S-BAND TESTS - Concluded

Te s t

Special

Pu rpose

Es tab l i sh PCM per formance rangea s a function of IPM.

Ver ify ef fec ts of upda ta phaser e v e r s a l .

"~ ~~

Resul t s

The IPM effects on BER increaseda s the modulating frequency de-creased. This degradat ion be-came s ign i f ican t ( 2 dB) a t P Mr a t e s of 50 Hz f o r a peak phasedeviation of 38". I t a l so wassigni fican t for PM rates of2000 Hz a t a peak phase devia-tion of 4 5 " . Bandlimited voicedegrada t ion increased morerap id ly wi th increas ing rmsphase deviation. The conclu-

s ions drawn were tha t IPM inex ce ss of 28" rm s sh ap ed ase i t he r a sine wave o r Gaussianbandlimited noise significantlydegraded the 5 1.2-kbpst e l eme t ry.

180" phase change was made,a ll messages we re r e j e c t e d .

~ -

Tes ts conf i rmed tha t , when a

~ ~ -~ ~"

" - - "

Special FM tests (B-2) . - The special FM channel tests were conducted joint lywith GSFC fr om Mar ch 7 to 21, 1966, to inves t igate possible problem areas in the L Mand the Block I1 CM FM transmi ssion l ink s. The primary area of con cer n was that theLM TV chan nel was ac-co upled ; and, for a very-low-frequency video waveform, theinform ation was great l y dis to rted. Also, when the video was completely different iated,the t ransmit ter peak-frequency deviat ion essent ial ly doubled. Other areas of concernincluded effects of freque ncy offset caused by os ci l la t or dr if t a nd Dopp ler effec ts anddeterminat ion of the opt imum FM demodulator configura t ion for cr i t ical FM modes.Both LM and Block I1 CM FM opera t iona l modes were tes ted . The FM t ran smi t te ru se d f o r t h i s t e s t was t he t r an smi t t e r a s soc i a t ed w i th t he USB tes t se t ; the FM t rans-mit ter, which is a direct-coupled device, was used to s imulate the LM tr an sm it t er bythe incorporat ion of an exte rna l ac netw ork .

To ach ieve the tes t ob jec t ive , t es t s of TV picture quality? TV channel signal-to-noise performance, PCM channel s ignal- to-noise performance, PCM BER, and spl it -phase te lemet ry s igna l - to -noise per formance an d BER were tes ted . Resul t s andcon clu sio ns fo r both LM and CSM confi gurat ions a r e presented in tab le IX.

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TABLE M . - FREQUENCY MODULATION TEST RESULTS

" "Lunar module configuration"

~ " _ _ _ _ ~ _ _ _The 4-MHz p refi l t ered demo dulat or im-

proved TV channel performance inthe th reshold reg ion; however, nor-mal operat ional mode (s ignal combi-nation 10) picture quality and BER(PCM 51.2 kbps r e a l t ime ) were notsignif icant ly improved over the un-filtered configuration when operatinga t t h e LM ca r r i e r c en t e r f r equ ency.

Offset frequ enci es of f 350 kH z had

little effect on TV channel perform-an ce fo r e i t he r t he p r e f i l t e r ed o runfiltered demodulator configuration;h owever, b it e r r o r r a t e s we re de -

graded n the r eg ion f rom l X 10 to4

1 X by such ffset requencieswhen the 4-MHz prefiltered demodu-la tor was used . ( F o r s o m e c a s e s ,degradat ion was more than for theunfiltered demodulation configuration.)

For o ff s e t f r equenc i e s more r ep r e sen -tative of lunar operatio ns (150 kHz).the 4-MHz prefi l tered demodulatorconfiguration indicated less degrada-t ion from the nomina l center fre -quency case than previously notedand s t i l l p rovided improved per form-ance over the unf i l t e red demodula torconfiguration at a l l signa l le vels ofi n t e r e s t .

Components caused by inter modul ation

of the 1.024 - and 1. 25-MHz sub-c a r r i e r ( 2 2 6 kHz o r mult iples thereof)did not appear in the demodulated TVs pe c t ru m.

_ _ _ _ . . _.

Command and service moduleconfiguration

The dc res tora t ion comple te ly res toredall low-frequency video informationand d id no t adverse ly a ffec t sys temperformance .

~

-~~

The 4-MHz prefiltered wide-loop de-modulator configuration was seriouslydegraded by car r i e r o ff se t f requen c iesOf -600 kHz.

The unf i l t e red nar row- loop per formance

fo r th e TV channel was essent ial ly a sgood a s the 4-MHz prefiltered con-f igurat ion and considerably bet ter forca r r i e r o f f s e t f r equenc i e s .

Acceptable picture quality was obtaineda t s i gna l - t o -no i s e r a t i o s i n to the TVmonitor which were less than re-quire d by the circu i t margin ICD fo rthe Block I1 CSM.

The s imula ted sp l i t -phase te lemet ry

channel test resul ts indicated thatimpro veme nt obtai ned by the 1-MHzpref i l t e r (approximate ly 6 dB) onlyheld t r ue at th e nominal c a r r i e r c e n -t e r f r equency,

Channel performance was degraded (fora 1-MHz prefi ltered confi gura tion)when offset frequencies of 54 00 o r? 500 kHz ( o r both) were s imulated.Channel performance for a l l demodu-lator configurations including condi-

tions of f 500-kHz ca r r i e r o ff s e tf requenc ies was apparen t ly adequatebased on expected received signallev els for 85-foot re mo te s i t es withcooled paramet r ic ampl i f ie rs (assum-ing no degradation of n oi se spe ct ra ldensi ty as a res ul t of rece ived signa llevels) .

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TABLE M . - FREQUENCY MODULATION TES T RES ULT S - Concluded

Lunar module configuration

Black-and-white patterns (low-frequencyvideo signals) could not be reprodu cedby th e LM TV cha nn el when th e lowf r a m e r a t e ( 0 . 6 2 5 f r a m e / s e c ) s y s t e mwas used witho ut the aid of dc res tor a-t ion at the TV monitor. The dc re-s t o r e r c o r r e c t e d f o r a completelydifferentiated signal, indicating thatadequate performance could be ex-pected for low-frequency pat terns byus ing dc res tora t ion .

Acceptable picture quality was obtaineda t s igna l - to -noise ra t ios in to the TVmonitor which were less than requi redby the Block I1 ci rc ui t ma rg in ICD.This was thought to be a re su lt of theBlock I1 synch roniz at ion burst formatproviding bet ter monitor synchroniza-tion at lower input signal-to-noiserat ios tha n when the synchronizat iont ip format (Block I) was used . "

~ -~ ~ ~

Command and service moduleconfiguration

All demodulator configurations produced

b it e r r o r a t e s of 1 X a t ece i ve drf signal levels weaker than the nominalexpec ted rece ived s igna l l eve l f romlunar dis ta nces. I t was noted hatrea l - t i me PCM was used dur ing a l l ofthe spl i t -phase telemetry BER tests ,and hence effects of t he tap e recor derwe re not p resen t in these da ta .

~"

High-gain/steerable antenna stat ic tests (B-3) . - During 1967. sev era l t es t s wereper formed to de te rmine s p a c e c r a f t m c o m p a t i b i l i t y with the spacecraft high-gain(CM) or s te er ab le (LM) antenna in the l ink. These tests were performed by usingspacecraft e lectronics , including the antenna, located in the Antenna Test Range/Anechoic Chamber Test Facility at IvISC. Th e MSFN USB RE R eq uipm en t us ed fo rt h e s e t e s t s was locat ed in the ESTL at MSC. Communication between the MSFN equip-ment and the spacecraft antenna/electronics was effected through a 16-foot-diameterparabolic-dish antenna located on the roof of the ESCF and through a similar (al thoughsmalle r) antenna locate d on the roof of the Antenna Test Range/Anechoic Chamber TestFacility. The distance between the antennas w a s approximately 1500 feet.

The LM s teera b le an tenna compat ib i l i ty tes t s were per formed in th ree s tage sdur ing the spr ing of 1967. Ini t ia l tests that used specif ied spacecraft and MSFNparame ters and t ransm iss ion modes were run in March 1967. Tes t s were essen t ia l lysta t ic in nature; hat is , no dynamic spacecraft motion was simul ated. Result s ofthese tes t s reve a led tha t pos i t i on e r rors (po in t ing e r rors ) of the L M s teerab le an tennawe re out of speci ficat ion. Analy sis of the prob lems indic ated that the prob able caus ewas IP M on the S-band up-link c a r r i e r, wh ic h in turn was caus ed by IAM of the up-vo i c e s ubca r r i e r. Fu r the r t e s t i ng con f i rmed t h i s p rob l em and i nd i ca t ed t ha t upvo i ce

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su bc ar rie r o sc il la to rs (SCO) with reduc ed IAM improved tracker performance to withinspecification; similar improvement was obtained by reduction of up-link c a rr i e r modu-lation indices. Subcarrier deviation changes had no significant effects on tr ac ke r er ro rperformance.

The CM high-gain antenna t e s ts were performed in November, us ing subcar r ie rswith improved AM cha rac ter ist ics and usi ng both specified and reduced modulation in-

dices . Resu lts were in agree ment with tests run with the LM steerable antenna andshowed that the reduced modulation indices and AM parameters allo wed an tenna p er-formance within specifications for the static conditions tested.

Frequency~ . . modulation. . demodulator. . .~ ~ threshold-extension- . . ." tes ts (B- 4). Study ofa n a l y s i s a n d t e s t i n g r e s d t s u p o the sum mer -of 1967 indicated conclusively that per-for man ce of the Apollo CM communications sys tem in the FM mode would be seriouslydegraded under certain operat ional modes at lunar distances. Particularly, playbacktelemetry and voice, as wel l as TV information, were expected to be poor. The iden-tified reasons were the following:

1. The sig nal lev el arr ivi ng at the MSFN rec eiv er was below the "threshold" of

the FM receiver-demo dulator combination.

2 . Th e per for man ce of th e MSFN FM demodula tor. opera ting in the below-threshold region, was less than specified.

Spacecraft transmit power was increased slightly by various means includingshortening of some cable leng ths, but the effective increase was not sufficient; and itw a s determined that the greatest improvement potential was on the MSFN. Thes eproblems, and tentat ive conclusions, were presented to Major General Samuel P.Phill ips of NASA Head qua rte rs at the Apollo Communi catio ns System Perfor mancepr es

apollo experience report electronic systems test program accomplishments and results

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