The Global Positioning System (GPS), is a global navigation satellite system (GNSS) that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. GPS has become ubiquitous technology that provides real-time positioning, navigation and timing (PNT) data in cars, boats, planes, trains, smartphones and wristwatches, and has enabled advances as wide-ranging as driverless cars, precision munitions, and automated supply chain management.
The GPS system provides critical positioning capabilities to military, civil, and commercial users around the world. However in many environments in which military operates (inside buildings, in urban canyons, under dense foliage, underwater, and underground) have limited or no GPS access. It can be significantly degraded or unavailable during solar storms.
GPS signals are also subject to electronic attacks such as jamming by adversaries. “Threats to military GPS have evolved and improved at a rapid pace — from a proliferation of small-scale commercial jamming devices that can readily be purchased on eBay to large-scale military anti-access/area-denial (A2/AD) capabilities,” said MAJ Christopher Brown, assistant program manager Dismounted PNT within the Assured PNT program.
GPS Constellation Upgradation
The United States’ Global Positioning System (GPS) was fully operational on July 17, 1995. However, advancements in technology and new demands on the existing system led to need to modernize the GPS system. The global, around-the-clock availability of navigation and precise time transfer provided by GPS of course rests largely on the mission capability of the NAVSTAR satellites.
The Government intends to use an evolutionary development approach. The Block acquisition approach follows the “Back to Basics” space program acquisition philosophy which focuses on mitigating cost and schedule risk through a lower risk incremental delivery of mature technologies. This approach, consistent with the National Security Space (NSS) 03-01 Acquisition Policy, focuses on mission success and on time delivery. This approach includes using a modular open systems architecture, standard interfaces and protocols, and continuous technology refresh, to incrementally improve system capabilities with a low risk of GPS service interruption.
As the legacy of GPS ages, so do many of these satellites. GPS constellations have grown through six major iterations since 1978. The sixth, GPS IIF, rose during the years 2010 to 2016. Those 12 satellites were all designed to last 12 years. The fourth-generation satellites, Block IIF, have many improvements over its predecessors to include longer life, improved reliability, more power, and a third civil signal capable of satisfying safety-of-life requirements for civil aviation. Some of their notable features include the ability to receive software uploads, better jamming resistance and increased accuracy. These new satellites will broadcast two new civil signals: one of which was introduced in 2003, the other in 2007. The added signals will increase the robustness of the civil service and improve accuracy to 3-5 meters.
The GPS III program objective is to develop and deploy improved systems architecture for the NAVSTAR Global Positioning System (GPS) to assure reliable and secure delivery of enhanced position, velocity, and timing (PVT) signals for the evolving needs of GPS civil and military users. GPS III has three times better accuracy and up to eight times improved anti-jamming capabilities. GPS III eliminates numerous existing shortcomings and vulnerabilities inherent in the current GPS architecture that threaten to severely impact vital civil commerce, transportation, public safety, as well as military operations in the future.
The U.S. Space Force, Space and Missile Systems Center (SMC) and its mission partners successfully launched the fourth GPS III satellite in Nov 2020 from Nov. 5 from Space Launch Complex 40 at Cape Canaveral Air Force Station, Florida. The Lockheed Martin-built satellite was carried to orbit aboard a Space Exploration Technologies Corporation (SpaceX) Falcon 9 launch vehicle. GPS III SV04 will join the current GPS constellation comprised of 31-operational spacecraft. GPS III, the newest generation of GPS satellites, brings new capabilities to users, including three times greater accuracy and up to eight times improved anti-jamming capabilities.
Tonya Ladwig, acting vice president for space navigation systems at Lockheed Martin, said on a Sept. 25 2020 call with reporters. “GPS III provides three times greater accuracy, and up to eight times improved anti-jamming power over satellites in existing constellations.” Spacecraft life will extend to 15 years, 25 percent longer than any of the GPS satellites on-orbit today. GPS III’s new L1C civil signal will also make it the first GPS satellite broadcasting a compatible signal with other international global navigation satellite systems, like Europe’s Galileo, improving connectivity for civilian users.
However, the full capability of the GPS III satellites will only be available to the users on the ground (or in the air, or at sea) in 2023 when a sufficient number of additional GPS III satellites have joined the constellation, and until a new ground control system comes online.
“As more GPS III satellites join the constellation, it will bring better service at a lower cost to a technology that is now fully woven into the fabric of any modern civilization,” stated Lt. Gen. John Thompson, commander of the U.S. Air Force’s Space and Missile Systems Center and the Air Force’s program executive officer for space.
GPS III enhances U.S. leadership in space-based navigation by meeting the stated Presidential goal of establishing GPS as a world standard. GPS III supports the Federal Radionavigation Plan and will be fully interoperable with all current global radionavigation systems.
The Air Force is pursuing a “Block” approach to GPS III space vehicle (SV) development and the next generation control segment (OCX) to rapidly respond to warfighter capability requirements. GPS III SV01 is the first of an entirely new, next generation GPS satellite designed to modernize the GPS constellation. The COps [the Second Space Operations Squadron] system will allow the U.S. Air Force to operationally command and control the GPS III satellites as well as legacy GPS satellites currently in the constellation.
GPS III satellites continue to roll off the production line at Lockheed Martin’s GPS III Processing Facility near Denver. The first satellite in the series was launched in December 2018, and the tenth and the final one is expected to be launched in 2023. In June 2020, the third GPS III satellite was successfully launched. SV03 joined the current GPS constellation comprising 31 operational spacecraft, and was the 22nd military-code capable satellite to the fleet. SV02 was Launched in Aug. 2019, GPS III SV01 , SV02 and SVo3 took their place in 31 satellite strong GPS constellation, which provides positioning, navigation and timing services to more than four billion civil, commercial and military users.
Those more-advanced satellites will comprise more than 12 percent of the GPS constellation once the fourth system is up and running. This satellite is the 23rd equipped with M-Code upgrades that protect against signal jamming, one short of the 24 needed for global coverage, Ladwig said. It is slated to become operational in mid-October, following post-launch tests and transfer to the Space Force personnel who oversee the constellation. The next six GPS III satellites in the pipeline are in various stages of fabrication and approval. Lockheed could also build up to 22 additional satellites that offer greater capabilities as part of a follow-on program.
SpaceX will begin reusing Falcon 9 boosters starting with the fifth GPS III launch, marking an important shift in rocket technology that aims to drive down the military’s cost of reaching orbit as space needs grow. “I am proud of our partnership with SpaceX that allowed us to successfully negotiate contract modifications for the upcoming GPS III missions that will save taxpayers $52.7 million while maintaining our unprecedented record of success,” Walt Lauderdale, the Space Force Space and Missile Systems Center’s Falcon Systems and Operations Division chief, said in a Sept. 25 release.
Earlier, the Space and Missile Systems Center had announced that on June 27, the Space Force took “a major step toward operational acceptance” of the M-Code, with Lockheed Martin’s completion of the M-Code Early Use (MCEU) hardware and software upgrade package for the GPS Operational Control System (OCS). However, OCS is Lockheed Martin’s stop-gap GPS control system built as a bridge to Raytheon’s long-troubled and much delayed Next Generation Operational Control Segment (OCX), which was originally designed specifically to handle the M-Code. The full-up OCX system is slated for delivery in 2021, and is expected to become operational in 2022.
Continued investment in GPS is important. Besides the military applications, the U.S. economic benefit of GPS is estimated to be over $300 billion per year and $1.4 trillion since inception.
GPS III / GPS Block III Satellites enhancements
The next generation will be composed of GPS III satellites are deisgned to be capable of meeting military and civil needs through 2030 which will include all of the legacy capabilities, plus the addition of high-powered, anti-jam military-code, along with other accuracy, reliability, and data integrity improvements. The system would provide a best value solution with the flexibility to anticipate and respond to future military and civilian needs.
The GPS III program includes an integrated space segment (SS) and control segment (CS) system that incorporates the Nuclear Detonation Detection System (NUDET) and defines the Signal-in-Space (SIS) to User Equipment (UE) interface. The GPS III security infrastructure would provide user access to and protection of the entire system. The GPS III system would facilitate the incorporation of additional mission capabilities (i.e. Blue Force Tracking (BFT), Search and Rescue (SAR) missions, etc.).
In a major departure from previous GPS designs, the M-code is intended to be broadcast from a high-gain directional antenna, in addition to a wide angle (full Earth) antenna. The directional antenna’s signal, termed a “spot beam”, is aimed at a specific region (i.e., several hundred kilometers in diameter) and increase the local signal strength by 20 dB (10× voltage field strength, 100× power). A side effect of having two antennas is that, for receivers inside the spot beam, the GPS satellite will appear to be two GPS satellites occupying the same position. While the full-Earth M-code signal is available on the Block IIR-M satellites, the spot beam antennas will not be available until the Block III satellites are deployed. Like the other new GPS signals, M-code is dependent on OCX.
GPS IIIA includes all of the GPS IIF capability plus up to a ten-fold increase in signal power, a new civil signal compatible with the European Union’s Galileo system, and a new spacecraft bus that will allow a growth path to future blocks. GPS III system is expected to have about 500 times the transmitter power of the current system, multiplying its resistance to jamming. This jam resistant, modernized version of the world’s greatest free utility will be developed and delivered to ensure the US has the most precise and secure positioning, navigation and timing capability. GPS III, will give new navigation warfare (NAVWAR) capabilities to shut off GPS service to a limited geographical location while providing GPS to US and allied forces.
Military Signal Power Up. Encrypted M-code signals will be up to eight times more powerful than currently. This makes them more reliable. but also enables the sats to overcome efforts to jam their signals. Other signals also offer increased signal power at the Earth’s surface. L1 and L2: −158.5 dBW for aC/A code signal and −161.5 dBW for the P(Y) code signal. L5 will be −154 dBW.
GPS III will offer significant improvements in navigation capabilities by improving interoperability and jam resistance. The GPS III system also incorporates the Nuclear Detonation Detection System (NDS) and provides a potential platform for supporting additional synergistic payloads and services. With a constellation of 30-32 satellites, GPS III will have Second and Third Frequencies to contain civilian signal, (L2 = 1227.60 MHz) & (L5 = 1176.45 MHz), more robust signal transmissions, and provide real-time unaugmented 1 meter accuracy.
For Lockheed Martin-built Block IIR and IIR-M and Boeing’s Block IIF satellites, signals shall be contained within two 20.46-MHz bands centered about the L1 and L2 nominal frequencies. For Block III and subsequent satellites, the requirements specified in this IS shall pertain to the signal contained within a 30.69MHz band centered about the L1 and L2 nominal frequencies.
GPS IIIA will maintain constellation sustainment, provide existing capabilities, plus introduction of a new L1C civil signal, increased earth coverage M-code power for authorized military users, a graceful growth path to achieve full CDD threshold requirements, and continuing support for the NDS mission, to serve the evolving needs of GPS military and civil users.
When fully deployed, the GPS III constellation will enable a cross-link command and control architecture, allowing the entire GPS constellation to be updated from a single ground station instead of waiting for each satellite to orbit in view of a ground antenna as well as a new spot beam capability for enhanced M-Code coverage and increased resistance to hostile jamming. All of these enhancements contribute to improved accuracy and assured availability for military and civilian users worldwide.
The GPS IIIF programme will support a Regional Military Protection capability that will increase anti-jam support in theatre in order to ensure the US and allied forces are not denied to GPS access in hostile environments. The satellites feature new L1C civil signal, which makes them the first ever GPS satellites to be interoperable with other international global navigation satellite systems such as Galileo. GPS IIIA will transmit a new civilian signal (L1C), which is designed to be highly interoperable with the European Galileo satellite navigation system signal and intended to be fully compatible and interoperable with those signals planned for broadcast on Japan’s Quazi-Zenith Satellite System (QZSS).
Each GPS IIIF satellite will also feature a fully digital navigation payload and include a laser retro-reflector array, which enables the positioning of on-orbit satellites to be refined with ground-based, laser precision. Fully digital navigation makes it like software defined payload that would be able to reprogram in orbit and maybe enhance capabilities desired in the future. “We used a flexible, modular architecture that would allow for the insertion of modern technologies and new airforce requirements in a low-risk manner.” According to Harris, the fully digital navigation payload will provide the ability to change and upgrade the satellites incrementally over mission life.
Inter-Satellite Links: Block IIIF satellites will carry laser retro-reflectors to enable orbit tracking independently of the satellites’ radio signals, which in turn will allow satellite clock errors to be disentangled from ephemeris errors. A standard feature of GLONASS, this is included in the Galileo positioning system, and was flown as an experiment on two older GPS satellites, 35 and 36.
GPS IIIA is the first of three GPS III increments and is the foundation for enhancements in later blocks. New capabilities on GPS IIIA will provide improved Position, Navigation, and Timing (PNT) services to the warfighter and civil users by improving accuracy, integrity, and resistance to hostile jamming. For military users, GPS IIIA satellites will provide further increases in the anti-jam capability of the M-Code signals.
GPS III program contracts
GPS IIIA is an Acquisition Category 1D program. The GPS must comply with 10 United States Code (USC) 2281 that requires that the Secretary of Defense ensure the continued sustainment and operation of GPS for military and civilian purposes and 42 USC 14712 and comply with certain standards and facilitates international cooperation.
Program funds support engineering studies and analyses, architectural engineering studies, trade studies, systems engineering, system development, test and evaluation efforts, and mission operations in support of upgrades and product improvements for military and civil applications necessary to support efforts to protect U.S. military and allies’ use of GPS.
The GPS III System Architecture and Requirements Definition (SARD) Phase was a 12-month study between government and industry. Two contractors (Lockheed Martin, Boeing) were awarded Firm Fixed Price contracts worth $16M per contractor. These were awarded 8 November 2000. Spectrum Astro also participated on company funds. GPS III SARD Phase products included Technical Requirements for Development Milestones; Architectures that support Technical Requirements; Life Cycle Cost estimates for each Architecture; Risk Analysis; Draft System Effectiveness and Performance Metrics; Initial Test and Evaluation Master Plan (TEMP); Acquisition Strategy; Entry/Exit criteria for Development Milestones; and a Technology Roadmap.
The procurement of the GPS III system is planned for multiple blocks, with the GPS IIIA portion currently underway. GPS III, the seventh generation, will launch eight more satellites to join SV01 & SV02 already in space. GPS III SV03 is scheduled to launch in late 2019, and SV04 in 2020. The final III payload should rise in 2023. From that point on, the follow-on era of GPS IIIF takes over.
In 2018, the Air Force selected Lockheed Martin to build up to 22 GPS IIIFs, adding new features and resiliency to the original GPS III satellite design. In spring 2018, Lockheed Martin submitted a proposal for the GPS III Follow On (GPS IIIF) program, which will add enhanced capabilities to the satellites. New hardware — a high-gain directional antenna — aims signals in a spot beam at a limited area, but blasts the signal at high power for strategic use by the military.
In late 2017, Lockheed announced a partnership with NEC Corporation to introduce artificial intelligence for computer learning in orbit. The company touted significant advances in processors and a move toward next-generation antennas, arrays and transmitters to drive more satellite flexibility, capability and resilience.
The US Government will also equip each Lockheed Martin satellite with a new search-and-rescue payload, which will help first responders detect and respond to emergency signals. Lockheed Martin Navigation Systems Mission Area programme manager Johnathon Caldwell said: “When we developed our design for the first ten GPS III, we used a flexible, modular architecture that would allow for the insertion of modern technologies and new airforce requirements in a low-risk manner.
GPS III’s military upgrades require new ground control stations, a replacement effort called OCX that has suffered repeated delays and cost increases, due to the complexity of the programming and requirements modifications. The new jamming-resistant military signal will not be available until the new, highly complex ground control system is available, and that is not expected until 2022 or 2023
Harris Corporation is a subcontractor to Lockheed Martin for development and production of GPS III Mission Data Units (MDUs) and transmitters for the GPS space section. Six have been delivered. The Harris MDU, together with the Atomic Frequency Standards and the L-band transmitter equipment, make up the Navigation Payload Element. The MDU performs the primary mission of the GPS satellite: generation of the navigation signals and data on a continuous basis. The MDU controls the generation of the precise timing signals used for navigation signals while distributing the timing signals to other satellite components.
The new Harris navigation payload offers a smooth transition to use of OCX. The payload for the first 10 GPS III satellites has been verified for OCX compatibility so the same OCX commands will seamlessly port to the Harris fully digital design, minimizing integration risks and associated costs.
“We’ve built a layered defense and implemented all information assurance requirements for the program into this system,” said Dave Wajsgras, president of Raytheon Intelligence, Information and Services. “The cyber threat will always change, so we’ve built OCX to evolve and to make sure it’s always operating at this level of protection.
“In addition, our GPS IIIF solution is based off a design already proven compatible with both the airforce’s next-generation operational control system (OCX) and the existing GPS constellation.”
Deliverables for GPS OCX are divided into three blocks. Block 0 delivery took place in fall 2017, enabling it to support the December launch. Block 1 delivery will take place in 2021, providing full operational capability to control both legacy and modernized satellites and signals. Block 2, delivered concurrently with Block 1, adds operational control of L1C and modernized M-code.
GPS III SV01 is the first of 10 GPS III satellites originally ordered by the Air Force. GPS III SV03-08 are now in various stages of assembly and test. In August, the Air Force declared the second GPS III “AFL” and, in November 2018, called GPS III SV02 up for a 2019 launch.
In September, the Air Force selected Lockheed Martin for the GPS III Follow On (GPS IIIF) program, an estimated $7.2 billion opportunity to build up to 22 additional GPS IIIF satellites with additional capabilities. GPS IIIF builds off Lockheed Martin’s existing modular GPS III, which was designed to evolve with new technology and changing mission needs.
NTS-3, America’s next experimental navigation satellite
Set to launch in 2023, NTS-3, America’s next experimental navigation satellite, will push the boundary of today’s position, navigation, and timing (PNT) technology to pave the way for a more flexible, robust, and resilient architecture for satellite navigation technology.
In 2019, the U.S. Air Force designated NTS-3 as one of three Vanguard programs, priority initiatives that integrate several technology components to deliver new game-changing capabilities, covering multiple domains and encompassing multidisciplinary solutions. Marked by enterprise commitment, Vanguard programs aim to deliver game-changing capabilities rapidly that transform future operations with cutting-edge technologies.
While the current constellation of GPS satellites operation in medium-Earth orbit, the NTS-3 satellite is destined for geosynchronous orbit. The decision to send NTS-3 to a different orbit — which was actually a pivot from the original plan to fly the experiment in MEO — was made deliberately as a way to test a hybrid PNT architecture concept, Joanna Hinks, AFRL’s NTS-3 deputy program manager, said.
She added that running the experiment in GEO does not mean a potential future constellation of these satellites would only operate in that orbit. Rather, it allows the program to prove whether signals coming from satellites in multiple orbits can offer a complimentary and improved capability for users on the ground.
NTS-3 will test a new digital signal generator that can be reprogrammed on-orbit, enabling it to broadcast new signals, improve performance by avoiding and defeating interference, and adding signatures to counter spoofing. AFRL will explore antenna configurations to provide Earth coverage and steerable regional beams in multiple frequencies and signal codes. Ultimately, NTS-3 will provide users with enhanced signal stability, availability, integrity and accuracy.
The NTS-3 GCS is compatible with the Enterprise Ground Services (EGS), an architecture that the Space Systems Command (SSC) is developing to provide a common system for satellite command and control. The goal is to move from a portfolio of stove piped ground systems to a single system that will connect with all Air Force and Space Force satellites, saving millions of dollars by streamlining user training and operations.
EGS will leverage big data and facilitate easier data sharing, situational awareness, and collaboration. The NTS-3 GCS will be backwards compatible with legacy ground systems, incorporate signal monitoring data from diverse sources, and leverage commercial antenna networks to maintain short-notice on-demand satellite control capability.
To ensure that user receiver equipment integrates seamlessly, the program team is developing software-defined PNT receivers that can rapidly respond to changing conditions. Like the on-orbit signal generator, the receivers are reprogrammable, thus increasing security and flexibility. They will readily adapt to warfighter needs and incorporate signals from the Galileo, QZSS, and other allied constellations since the experiment results and technology in NTS-3 will ultimately transition to the national space community.