harris and gps technology evolving a global utility and gps technology evolving a global utility...

Harris and GPS TechnologyEvolving a Global Utility

James PhelanHarris Corporation

Harris and GPS Technology

TABLE OF CONTENTSINTRODUCTION ..............................................................................................2

Harris Payload Legacy and Expertise ........................................................2GPS III MDU Capabilities ............................................................................5Digital Waveform Generator ....................................................................6Harris Payloads and GPS-Related Technology Development ..................9Harris FPGA Technology ...........................................................................10On-orbit Reprogrammable Technology .................................................11

SUMMARY ....................................................................................................12

LIST OF FIGURES

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Figure 1. Current GPS Vehicles ......................................................................2Figure 2. GPS Control and Monitor Stations ...............................................4Figure 3. GPS Block IIR/IIRM Mission Data Unit (MDU) ...............................5Figure 4. GPS III MDU Design for MEO Orbit ..............................................5Figure 5. First Operational Waveform Generator with M-Code (IIRM) ................................................................................................6Figure 6. GPS III Mission Data Unit with Embedded Waveform Generator ....................................................................................7Figure 7. FDWG Used in Pseudolite Demonstration ...................................7Figure 8. Small GPS Satellite Architecture with FDWG ...............................8

Figure 9. Harris Program Waveform Generation ........................................8

LIST OF TABLESTable 1. Historical Harris Technology in the GPS Program .........................3Table 2. GPS IIIA MDU Code Generation Flexibility ....................................6Table 3. New Software Builds .....................................................................10


Vehicle Data GPS IIA GPS IIR GPS IIRM GPS IIF

Signals L1 C/A, L1 and

L2 P(Y)

L1 C/A, L1 and

L2 P(Y)

L1 C/A, L1 and L2

P(Y), L2C, M-Code

L1 C/A, L1 and L2

P(Y), L2C, M-Code L5

Design Life 7.5 Years 7.5 Years 7.5 Years 12 Years

Launch Period 1990-1997 1997-2004 2005-2007 2010-Present

Currently Active 2 12 7 9

Figure 1. Current GPS Vehicles


Evolving a Global Utility

INTRODUCTIONHarris Corporation is a leading technology innovator, solving our customers’ toughest mission-critical challenges by providing solutions that connect, inform and protect. Harris supports customers in more than 125 countries and has 22,000 employees—including 9,000 engineers and scientists—worldwide. The company is organized into four business segments: Communication Systems, Space and Intelligence Systems, Electronic Systems, and Critical Networks. The Harris Clifton, N.J., facility has been providing integral technology for the Global Positioning System (GPS) Space Segment Navigation Payload since the program’s inception.

During the Labor Day weekend of 1973, military officers meeting at the Pentagon developed a GPS concept based on technologies developed under earlier mission-specific navigation programs. Between 1978 and 1985, ten prototype satellites were developed and launched to test the concept. The navigation signals these prototypes provided—and all subsequent U.S. GPS satellites—have consistently been furnished by high-signal-quality Harris Corporation transmitters.

This paper documents Harris’ past, present, and future efforts to support United States dominance in this important global utility. In 2013 alone, GPS contributed more than $68 billion to the U.S. economy. From waveform generation to transmission, command, and control to precise timekeeping technology you’ll learn how Harris continues to advance technologies that apply specifically to the GPS constellation.

Harris Payload Legacy and ExpertiseHarris navigation payload technology has been present on every U.S. GPS satellite ever launched. Harris first contributed to GPS in the 1970s, supporting the transmission of L-Band navigation signals in the first Block I GPS satellites. At the time, our customers turned to Harris for our expertise with the Radio Frequency (RF) spectrum from our deep experience reaching back to World War II. For GPS Blocks I and II/IIA, Harris continued to provide RF payloads for 40 satellite systems delivered from the 1970s through the 1980s.

Harris leveraged this experience when providing full navigation payloads to Lockheed Martin for the Block IIR program from 1988 through 1999. Harris also brought several innovations to the IIR program including improved time keeping, accuracy, and security for the nation’s GPS satellites. Harris continued to improve GPS payload technologies for IIR, IIF, and today’s GPS III modernization program.

Harris provides the entire navigation payload—as well as key elements of the Ultra High Frequency (UHF) Crosslink processing—for most of the active constellation. In the remaining space vehicles, Harris provides the navigation L-Band transmission equipment. Figure 1 shows past and present GPS Satellite types while Table 1 lists the Harris navigation content within the various GPS Space Vehicle types.

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As of October 2015, there have been 71 GPS satellites launched. Today, there are 31 operational satellites in orbit. They continuously send signals to Earth to help receiving devices like smartphones and vehicles determine their location. Since the 1970s, GPS satellites have logged more than 750 years of cumulative, on-orbit operations, without a single failure due to Harris equipment. In fact, many of the satellites have outlived their expected operation by several years.

For Block I, between 1978 and 1985, Rockwell International subcontracted to Harris to provide the navigational payloads for the first block of GPS satellites, which were intended solely for military use.

For Block II and IIA, which launched between 1990 and 1997, Harris provided 28 flight payloads. Part of the payload Harris delivered for Blocks I and II was the signal conversion portion, which converted a digital signal generated by the satellite to radio frequency (RF) energy to be beamed to the ground.

Harris saw its role expanded in the program for Block IIR from 1997 to 2004, when it teamed with new prime contractor Lockheed Martin to provide the entire navigation payload, including sophisticated atomic clocks, rather than just the signal conversion portion.

Next came Block IIF, but with a new prime contractor, Boeing. Harris and Lockheed were concerned they would not be involved with this portion of the program. Instead, the customer decided to retrofit some IIR payloads—several had yet to launch—to upgrade that system with some capabilities from the IIF satellites, including a modernized, more powerful signal. The Air Force was impressed and the IIR Modernization, or IIRM program, was born.

Harris engineers upgraded eight IIR payloads and delivered them to the Air Force before the first new IIF vehicle was even built. As a result, Boeing subcontracted Harris to work on the navigation payloads of the IIF program.

Moving forward, the Harris-Lockheed team is working on eight navigational payloads for the next generation satellites of GPS: Block III. The advanced payload will deliver signals with three times more accuracy, provide dramatically improved anti-jamming capabilities, and extend satellite life to 15 years.

For civilians, the signal will reach users more effectively. The newest signal will be capable of penetrating heavy tree cover to reach cars in wooded areas or pedestrians in an urban jungle. For the military, the signal will provide location accuracy down to sub-meter levels and be even more dependable due to improved anti-jam capabilities.

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GPS Navigation Payloads I II/IIA IIR/IIRM IIF III

L1 XMTR • • • • •

L2 XMTR • • • • •

L3 XMTR • •

L5 XMTR • •

RAFS • •

CAFS • •

MDU • •

Waveform Generator • • •

Fine Phase Meter VCXO and Code Loop TKS • •

TRIPLEXER • • • •

CROSSLINK •

L3 Filter • •

On-orbit Support • • • • •

Payloads Produced 12 28 21 12 TBD

Table 1. Historical Harris Technology in the GPS Program


Harris has also continuously supported the GPS Constellation Health and Maintenance efforts since 1997. Those efforts include:

• Investigatingorbitsignalanomalies

• Determiningtherootcause

• Identifyingwork-arounds

• Makingsoftwarechanges

• Performingequipmentswitchovers

• Preparinganomalyreports

• MonitoringthehealthandperformanceoftheIIR/IIRMSpaceVehicles

• EnsuringthattheGPSConstellationprovidestherequiredperformancetoboth the civil and military communities

Harris provides operational support, control, and maintenance for the current GPS Constellation (reference Figure 2), the GPS IIA and IIF satellites, and will also support the navigation payload for GPS III once it is launched.

Finally, Harris is currently developing all of the GPS III Navigation Payload Control Software on the OCX Program (Next Generation Operational Control Segment). As a Raytheon subcontractor, Harris’ software efforts involve setting the stage for secure uploads that provide the precise ephemeris and timing required by the GPS space vehicles. Other responsibilities for OCX include:

• Developingthecommandsoftwareanddataforthecurrentwaveformgenerator to produce the various signal structures

• DevelopingandproducingType1MissionCryptoandMonitorStationReceiver (OMSRE)

• Assessingoverallperformanceandthesoftwareforgeneratinguploadstothe Mission Data Unit (MDU) payload

• AssistingLockheedMartinindevelopingtheLaunchCheckoutSystemthat will provide early command and control capability prior to the formal validation of the OCX System

The GPS IIR/IIRM Mission Data Unit is shown in Figure 3. It is currently performing the navigation mission on the majority of the active GPS Satellites. This fully redundant system can operate through the natural radiation hazards in the Medium Earth Orbit (MEO). It is also hardened against manmade radiation effects. With this MDU, Harris initiated the on-orbit reprogrammable capability to updated software via the Master Control Segment. This technique has been used for 18 years to address anomalies and add new functionality to the GPS Constellation. The software code for this application was written in the ADA language to facilitate such modifications.

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Figure 2. GPS Control and Monitor Stations


GPS III MDU CapabilitiesThe Harris Mission Data Unit for GPS III is shown on the right side of Figure 4. It’s a modular, fully redundant system that is radiation tolerant to both the MEO (Reference Figure 4, left) as well as manmade effects. The MDU is the main command and control center for the navigation mission. It provides precise timing, generates all GPS waveforms, and provides health and status messages via its S-Band serial telemetry link. The MDU accepts daily uploads from the GPS Control Segment, which provides all the military and civilian data required to generate GPS signals.

For GPS III, the U.S. Air Force envisioned an entirely new block of GPS satellites—unlike any that had come before. They wanted the new Block III to include the ability to “spiral in” advanced technology as risk is reduced and therefore meet evolving warfighter needs. New modular technology within GPS Block III satellites enables this spiral development.

Harris has enhanced the IIR/IIRM MDU to include both the Waveform Generator functions and the Synthesizer MOD/IPA functions. These two functions were assembled independently in the previous GPS design. The MDU also contains a more advanced microprocessor and memory than the original 1750A Silicon on Sapphire-based product. The modular design of GPS III satellites enables insertion of these advanced technologies.

The GPS III MDU consists of individual circuit cards, which support Timekeeping (TKS), Waveform Generation (WG), Cryptography, I/O, and Peripheral functions. The Flight Software (resident on the SBC circuit cards) provides all the algorithms and data processing required for generating the User Navigation Data. It also includes the software logic required to support command, control, maintenance, integrity and telemetry functions. Spare Circuit Card Assembly (CCA) slots are allocated for accommodating future functional enhancements.

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Figure 3. GPS Block IIR/IIRM Mission Data Unit (MDU)

Figure 4. GPS III MDU Design for MEO Orbit


The GPS III MDU contains a flexible code generation and signal combining system which supports separate M-Code transmitters, the ability to move codes between transmitters, and the generation of new codes on-orbit using Flex Code generators as shown in Table 2. All codes and navigation data are generated by the MDU for transmission by the L-Band System. This includes the following codes and data, C/A, P(Y), L1-M, L2-M, L1CP, L1CD, L2C, L3, L5I, L5Q, NAV, MNAV, CNAV and CNAV-2 data.

The GPS III MDU also contains a unique closed-loop timekeeping system that maintains accurate timing for precise positioning. For example, 1ns/1 billionth of a second represents one foot of navigation error. The GPS III MDU distributes this precise timing throughout the GPS Space Vehicle for use by other payloads. The Microsemi VCXO provides short-term stability while the Excelitas RAFS provides long term stability—all under the guidance of a proprietary Harris Control Loop and Betting Logic algorithm. A sampling clock and an array of fine-phase meters complete the MDU components required for timekeeping. Finally, the MDU provides secure, encrypted functions to support the Navigation and Nuclear Detection Missions.

Digital Waveform GeneratorSince GPS Block I was awarded in 1974, Harris has led next-generation GPS payload technology. Our ongoing investment in research and development has directly contributed to the extraordinary advancements seen in today’s robust GPS constellation.

Harris has researched and invested in digital payload technology for over a decade. In 2004, we demonstrated our first direct digital-to-RF waveform generator by successfully producing and receiving legacy GPS signals and Pseudo M-code. It was part of the GPS IIR/IIRM Program, which introduced L2C, M-Code and a demonstration L5 Signal to the GPS Constellation. Twelve GPS IIR’s and eight GPS IIRM’s were launched containing this waveform generation technology including the associated M-Code crypto algorithms (reference Figure 5). Then, in 2010, we used our second-generation digital waveform generator design to demonstrate the new L1C GPS signal.

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Carrier Valid PRN Codes Per Carrier4

L1 EC C/A3 P(Y)2 L1M L1Cd L1Cp 2 Flexible1

L1 MEC C/A3 P(Y)2 L1M L1Cd L1Cp

L2 EC C/A3 P(Y)2 L2M L2C 2 Flexible1

L2 MEC C/A3 P(Y)2 L2M L2C

L5 EC L5I L5Q 2 Flexible1

Notes:1. T wo Flexible, On-Orbit Programmable Code Generators per carrier, which are shared between

the EC and MEC transmit chains.2. Single P(Y) code generator shared between L1 and L2 transmit chains.3. Single C/A code generator shared between L1 and L2 transmit chains.4. Codes on a specific carrier (L1, L2) can only be transmitted on one aperture (EC or MEC) at a time. Example: C/A code on L1 can only be transmitted on the L1 EC transmitter or the L1 MEC transmitter, not both simultaneously.

Legend: Nominal Codes on Transmit Chain

Table 2. GPS IIIA MDU Code Generation Flexibility

Figure 5. First Operational Waveform Generator with M-Code (IIRM)


In 2013, as part of the GPS III development program, Harris demonstrated digital signal capability for the navigation payload at a preliminary design level. The preliminary design was reviewed to the rigorous standards of a tailored military-standard process and included a formal study by our customers, clearly identifying the maturity of the navigation payload design. Harris customers documented the design’s technical adequacy, risk resolution, approach, and technical risk.

The GPS III payload Harris is now developing for the U.S. Air Force is the most capable navigation satellite payload ever produced. We believe the combination of our proven GPS heritage, our skill in the RF spectrum, satellite communications and reprogrammable payload, and our continued investment in research all uniquely qualify us to support the next generation of GPS satellites.

Harris incorporated a more advanced Waveform Generator within the GPS III Mission Data Unit (MDU). This design iteration addresses the SS-SS-800 signal flexibility requirements imposed upon the GPS III program, specifically the flexibility for adding new codes and signals (reference Figure 6).

During the development of the GPS III Program, Harris funded multiple programs to further digitize the waveform generator. We explored the available technology for supporting on-orbit reprogrammability and developed predistortion techniques for further improving signal quality. Harris is actively pursuing the potential use of its digital navigation waveform generation technology on numerous domestic and international platforms.

Also in 2012, Harris utilized the Advanced Navigation Receiver (ANR) and Flexible Digital Waveform Generator (FDWG) to produce and monitor Pseudolite Navigation Signals for use in a flight demonstration over the Mojave Desert. Figure 7 shows the FDWG used during this successful pseudolite flight testing.

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Figure 6. GPS III Mission Data Unit with Embedded Waveform Generator

Figure 7. FDWG Used in Pseudolite Demonstration


Harris continued to evolve the design of the FDWG during our Small GPS Satellite Study. The design iteration combined the GPS III Waveform Generator and Synthesizer/Modulator/Intermediate Power Amplifier (SMIL) functions within one CCA. The characteristics of this design are being leveraged further to improve this technology (Reference Figure 8).

• LeveragesGPSIIIMDUSoftware

• ImprovesRFPerformanceandSignalFlexibility

• CombinesSignalsEfficiently

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Figure 8. Small GPS Satellite Architecture with FDWG

Figure 9. Harris Program Waveform Generation

| 1Presentation Title Harris Proprietary Information

Fully Programmable Modulation Techniques –

Up to 7 Codes Using IntervoteModulation

Direct-to-L-Band Digital Waveform Generator

includes Flexible Carrier Frequency, Single-

Sideband Signal, Multiple Modulation Schemes

Migrated the All-Digital Waveform Generator to a

Space Qual Package

Fully Implemented and Demonstrated Waveform Generator Using POCET

Combining, COPAC Combining Algorithm

Developed and Implemented

Advanced Waveform Generation

On-Orbit Interplex Signal Combining for C/A, P(Y), M-Code, and

L2-C Code Generation

On-Orbit QPSK C/A and P(Y) Code Generation

Advanced Waveform Generation Meeting

GPS III Specifications

HarrisWaveform Generation

Investment

Harris GPS Program Waveform Generation

Experience

All-Digital DDS Based, Multiple GNSS Capable, Fully On-Orbit Reprogrammable

Reduced SWAPC Flexible Power Consumption

Combining Algorithm

Investment

Space-Based Digital Waveform

Generator (2006-2008)

All-Digital Waveform Generator

(2003-2006)

Digital Waveform Generator

(2001-2003)

GPS III MDUDevelopment

GPS IIR-M Waveform Generation

GPS IIR Waveform Generation

Figure 9 shows Harris’ previous developments in waveform generation. Ever since GPS IIR, Harris has continuously developed waveform generation and is combining algorithms to advance GPS navigation. We apply both our experience and signal quality test equipment to ensure new waveforms meet the latest in GPS signal-in-space requirements.

Harris waveform generation research will enhance the on-orbit signal flexibility of GPS payloads. It will enable implementation of more modulation types such as *M-ary Phase Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM). To further improve efficiency, the technology will support precise tuning of code power ratios and reduce spurious emissions. Finally, this research will support the implementation of more efficient signal combining techniques such as Aerospace’s Phased Optimized Constant Envelope Transmission (POCET) algorithm, as well as others designed to reduce power loss.


Harris is committed to continuing our legacy of innovation in GPS navigation payloads and will keep investing in digital technology, ensuring we are positioned to meet evolving GPS program and warfighter needs.

Harris GPS-Related Technology DevelopmentHarris continues to pursue these GPS-related topics:

• NewSignalCombiningTechniques-Harrisisexploringandvalidatingconstant envelope signal combining techniques

• AdvancedTimekeeping-Harrishasamulti-yearprogramtoexploreadvanced timekeeping capabilities for positioning, navigation, and timing (PNT) systems. The project explores advanced timekeeping and integrity monitoring algorithms to produce enhanced signal stability, plus anomaly detection and correction

• HigherGainGaNAmplifiersToReduceDCPowerConsumption

- Reduces out-of-band emission profile

- Supports regional military protection requirements

• EnhancedWaveformTechnology

- Reduces spectral bandwidth

- Improves transmitter efficiency

- Reduces out-of-band emissions

• PhasedArrayAntennaTechnology

- Alternative technology for navigation signal transmission

- Alternative technology for regional military protection requirements

Harris FPGA TechnologyHarris is advancing waveform generation through innovative and unique (constant envelope) signal combining and wave-shaping algorithms. We are currently developing elements for a single card design that will provide all waveform generation and cryptographic functions, plus authenticate and process encrypted uploads.

Harris is leveraging previous GPS waveform generation through the use of On-Orbit Reprogrammable Technology. These advancements will improve GPS through:• Theminiaturizationofthewaveformgeneratorandfulldigital

implementation, which will enable improvements in many critical PNT signal characteristics such as group delay, signal coherence, quadrature phase error, phase noise, and correlation loss

• Theuseofaradiationhardenedon-orbitreprogrammabletechnology,in conjunction with new processors, provides a higher degree of on-orbit flexibility

• Theadditionofnewrangingcodesandfrequencies(e.g.L5)inthepasthastaken 10 years or more to go from conception to broadcasting in space. This technology will allow new signals to be dynamically added

Harris’ investment in these technologies will lead to an affordable, small-size, low-weight-and-power design that can be readily programmed on-orbit to produce any of the various pre-defined navigation signals (GPS, Glonass, Galileo, Beidou, etc.), as well as to accommodate future waveforms. The architecture will also support U.S Cryptographic algorithms necessary for producing GPS waveforms.

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On-orbit Reprogrammable TechnologyHarris Corporation pioneered the introduction of on-orbit reprogramming in the GPS Block IIR series of Space Vehicles. All GPS Block IIR/IIRM Space Vehicles can be reprogrammed while on-orbit. This unique feature has enabled diagnostic activity, lessons learned and new enhancements. Indeed, the GPS Block IIR processor software design has evolved under the GPS Phase IIC Program, addressing a large list of user enhancements as well as providing workarounds for unforeseen events affecting IIR/IIR-M performance.

New Software Versions (6 thru 14) that have been successfully uploaded to the IIR/IIRM Space Vehicles are shown in Table 3. Harris continues to invest in the evolution of this technology, including research in new processors, non-volatile memory, and radiation hardened devices and processes.

Harris has extensive experience in dealing with natural and manmade radiation effects. We understand, quantify, and mitigate the mission impacts for various mission durations and orbits. We have successfully put ASICs and FPGAs to work for space applications, including the use of OTP FPGAs on the GPS IIR/M and GPS III Programs.

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Mission Processor Operational Build Date Pre- or Post- Launch

OB 1 03/25/1996 Pre-Launch





OB 6 03/15/1998 Post Launch Upload

OB 6.1 04/15/1998 Post Launch Upload






OB 10.1A 11/30/2004 Post Launch Upload




OB 13 12/09/2011 TBD

Table 3. New Software Builds

SUMMARYHarris Corporation is constantly improving GPS navigation payload technology. We have proven this commitment many times through our contributions to past and present GPS program missions. We continually commit significant internal funding to research and development. Harris also supports AFRL and related small-business research efforts to improve GPS technology through the SBIR Program and others. We are currently investing in all areas pertinent to the navigation payload:

• DigitalWaveformGeneration

• TimekeepingSystemandAtomicFrequencyStandards

• L-BandTransmissionandFilterTechnology

• HighSpeedRadiationHardenedProcessorsandMemory

These efforts all pertain to the long term goal of providing high accuracy (currently 16 M Spherical Error Probable) for users in all circumstances and conditions.

harris and gps technology evolving a global utility and gps technology evolving a global utility...

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