The GPS Next Generation Operational Control System program of the U.S. Space Force has been cancelled by the Defense Acquisition Executive, based upon the recommendation of the acting service acquisition executive.
OCX was intended to update command and control of the GPS satellite constellation, replacing the current system, known as the Architecture Evolution Plan (AEP), as well as replacing the Launch, Anomaly and Disposal Operations system. However, the program was unable to deliver needed capabilities on an operationally relevant timeline at an acceptable level of risk to meet the GPS constellation modernization needs.
“It’s important we refine and update acquisition processes to prioritize rapid, incremental capability delivery versus complex ‘all or nothing’ system deliveries,” said Acting Service Acquisition Executive Tom Ainsworth. “The Department of War [Defense] has made clear that we need to deliver warfighting capability at a faster rate. We must continue to work with industry to meet the needs of our warfighters as we focus on delivering the right technology on the right timeline to enhance our capabilities and maintain space superiority.”
In July 2025, following a multi-year regimen of factory testing, the Space Force contractually accepted OCX from RTX (Raytheon) and began extensive integrated systems testing to resolve liens carried over from factory testing, as well as to ensure the system could operate within the broader GPS enterprise of ground systems, satellites, and user equipment.
As of January 2026, the program cost was approximately $6.27 billion which included complete Raytheon funding to date and other government costs, such as the cost of government testing and support costs to the OCX acquisition program office.
“Regrettably, extensive system issues arose during the integrated testing of OCX with the broader GPS enterprise,” said Mission Delta 31 Commander Col. Stephen Hobbs. “Despite repeated collaborative approaches by the entire government and contractor team, the challenges of onboarding the system in an operationally relevant timeline proved insurmountable. We discovered problems across a broad range of capability areas that would put current GPS military and civilian capabilities at risk.”
Because of past delays on the OCX program, the Space Force has made incremental improvements over the last 10 years to AEP. These successful upgrades provide confidence that further upgrades to GPS ground systems will continue to support the enterprise and deliver new capabilities.
“Ultimately, we analyzed the work remaining on OCX and compared this with the current GPS control system capability,” Hobbs said. “The analysis revealed additional investment in OCX was no longer the best solution for protecting and advancing GPS capabilities. Instead, we will continue enhancing the current control system to operate the GPS satellite constellation.”
The U.S. Space Force is considering canceling the contract held by RTX (formerly Raytheon) to develop the GPS III ground control system, according to a report in Air & Space Forces Magazine.
GPS OCX, the Next-Generation Operational Control Segment, has long been beleagured by cost overruns and deadline delays. Established in 2010, the GPS OCX program was planned to begin operations in 2016. In 2010, Raytheon (now RTX) was contracted to develop a modernized ground control system to support the upcoming GPS Block III satellite constellation.
The first GPS III satellite, built by Lockheed Martin, launched in 2018. Eight more have followed, with the 10th satellite awaiting launch on a SpaceX Falcon 9 rocket within the next few months. With 32 GPS satellites on orbit, the Space Force is relying on the OCX software to utilize the advanced GPS III capabilities for jam-resistance and precise navigation.
In July 2025, RTX began a government-led testing phase, but the tests revealed software defects.
The U.S. Space Force’s Space Operations Command has accepted a modernized operating system for GPS, designed to maintain the resiliency of the constellation and enhance positioning, navigation and timing (PNT) services to meet evolving user demands.
The GPS Next Generation Operational Control System (OCX) upgrade is part of a broader set of Space Systems Command acquisition programs designed to deliver a range of modernized capabilities across the GPS III enterprise. In addition to OCX, these programs include the GPS III/IIIF satellite vehicles and Military GPS User Equipment.
The modernization effort is expected to improve signal access in electronically contested environments, increase the system’s ability to detect failures, enhance position and time transfer accuracy, and strengthen the integrity and uninterrupted availability of the Military Code.
“One of our missions is to deliver sustained, reliable GPS capabilities to America’s warfighters, our allies, and civilian users,” said Cordell DeLaPena, program executive officer for military communications and PNT at Space Systems Command. “The current enterprise modernization efforts underway give users confidence that GPS will continue to provide worldwide premier PNT service.”
Mission Delta 31, in partnership with Space Systems Command, developed a systematic process involving transition exercises, rehearsals and constellation transfer trials to verify the system’s integrity and capability prior to full transfer, according to Col. Stephen Hobbs, commander of Mission Delta 31. Hobbs added that risk reduction activities are underway to demonstrate OCX’s ability to integrate with existing, on-orbit GPS satellites.
Raytheon initiated the delivery of OCX to the U.S. government with the submission of the Department of Defense Form 250 on July 1, 2025. Following acceptance, Mission Delta 31 will continue integrated systems testing, operational readiness exercises and preparations for the eventual transfer of the GPS constellation to the new system.
“Testing and transition events will continue until the system is ready to transfer to operations, which is expected in late 2025,” said Hobbs. “Technology in space is advancing at lightning speed, with many new players from around the world. To continue providing reliable GPS for everyone, from your smartphone map to critical military operations, innovation is vital. Modernizing GPS is key in maintaining this essential service and remaining a leader in Space.”
The U.S. Space Force’s Space Systems Command (SSC) has awarded Raytheon a $196.7 million contract extension for the GPS Next Generation Operational Control System (OCX) program — despite being years behind schedule. This latest award brings the total OCX contract value to nearly $4.5 billion since its inception in 2010. However, according to the U.S. Government Accountability Office (GAO), the total amount is approaching $8 billion.
The OCX program, designed to enhance GPS infrastructure, has faced significant setbacks. It is currently about seven years behind the original schedule, with the GAO reporting that the system of 17 ground stations was not ready by its October 2024 deadline. Further testing is required for the system to be operational by December 2025.
Despite these challenges, OCX remains critical for modernizing GPS capabilities. The system will enable full M-Code capabilities, providing jamming-resistant GPS signals for military operations in contested environments. OCX is also designed to improve cybersecurity for both military and civilian applications significantly. Once operational, OCX will command all modernized and legacy GPS satellites, managing all civil and military navigation signals.
The program has faced scrutiny due to its delays and cost overruns. The GAO has flagged the program’s delays as a risk to the GPS enterprise, while lawmakers have expressed frustration over the delays and budget increases. Despite this, the Space Force continues investing in the program to enhance GPS capabilities for military and civilian users. OCX is expected to provide improved accuracy, availability and resistance to jamming compared to the previous ground control segment. The system will also support the launch and operation of GPS III satellites.
New GPS ground stations that are contracted by Raytheon Technologies to replace the current ground stations have been delayed until July 2025, the Pentagon’s testing office reported.
The Next Generation Operational Control System (OCX) is facing a new delay of 16 months, according to the 2023 Annual Report of the Director of Operational Test & Evaluation (DOT&E).
More than seven years behind schedule, the continuous delays have caused the U.S. Department of Defense (DOD) to go over its yearly budget and have sparked discussions as to future budget allocations for the U.S. Space Force (USSF) to continue to control and enhance the GPS constellation.
“These delays increase the risk that U.S. and allied warfighters will be unable to conduct successful operations in future contested environments due to the lack of access to modernized GPS position, navigation, and timing (PNT) information,” the Pentagon’s testing office said in a statement.
The M-Code can now be broadcast on 21 of the 31 GPS satellites in orbit. However, it is only available to a small number of military personnel due to both the OCX issue and a lack of radios and receivers equipped to access it.
The Space Force has a Military GPS User Equipment (MGUE) program underway to develop new computer chip-carrying cards to retrofit existing platforms, such as aircraft and ships, so they can ingest M-code signals, as well as to develop a new handheld receiver. This effort has also experienced delays, according to a June 2023 report by the Government Accountability Office.
The 2024 DOT&E report notes that because of the delays in the development of the MGUE receiver cards, the Army and Marine Corps are now buying commercially developed receivers capable of ingesting the M-Code for fielding with ground vehicles.
Additionally, the DOT&E report cautions that because the OCX software is designed to be the basis for an upgraded system, OCX Block 3F, designed to control the planned next generation of GPS satellites called GPS IIIF, that effort also is likely to be delayed. The Space Force intends to launch the first GPS IIIF satellite in 2027.
Currently, 37 Global Positioning System satellites are on-orbit, with 29 of them set healthy. The system continues to provide an average 48-centimeter position accuracy. Despite this achievement, the U.S. government — specifically, the Space Force — continues to modernize GPS’s space, control and military user equipment segments.
Modernization of the space segment is centered on the GPS III satellites, which provide up to eight times better anti-jam capability and a new L1C signal to improve user connectivity. GPS IIIF satellites, scheduled for delivery starting in early 2026, will add a search-and-rescue payload, a fully digital navigation payload, and greatly enhanced anti-jam capability for military operations.
Modernization of the control segment is focused on the next-generation Operational Control System (OCX), scheduled to become operational early next year. OCX will sport an updated architecture to provide enhanced command-and-control capabilities and enhanced cybersecurity. Despite the pandemic, all 17 global OCX monitoring station installations were completed last summer, and most of the remaining equipment was fielded by the end of 2021.
Twenty-four GPS satellites are broadcasting the military code (M-code). The Modernized GPS User Equipment (MGUE) program is developing military GPS receivers able to take advantage of these signals to improve defenses against spoofing and jamming while allowing navigation warfare operations.
On the civil side, GPS modernization will play a key role in the development of the Next Generation Air Transportation System and intelligent transportation systems. The Department of Defense coordinates its GPS activities with the Department of Transportation (DOT), the Federal Aviation Administration (FAA) and many other federal departments and agencies via the National Executive Committee for Space-Based PNT. The term “space-based PNT” refers to GPS, GPS augmentations and other GNSS.
However, this government-wide coordination and cooperation is contradicted by the stand of the Federal Communications Commission (FCC) on the matter of Ligado Networks’ applications to modify its license for terrestrial service, which it approved in 2020. The FCC’s decision is opposed by the executive branch, represented by the National Telecommunications and Information Administration (NTIA), and by 14 federal agencies and departments individually (including the departments of Defense, Transportation, State, Treasury, Justice, Interior, Agriculture, Commerce, Energy and Homeland Security), as well as by the National PNT Advisory Board and by most GNSS receiver manufacturers and aviation organizations. NTIA took the unprecedented step of filing a still-pending petition for reconsideration with the FCC. The concern is that Ligado’s proposed transmission power exceeds the thresholds established by the DOT’s April 2018 GPS Adjacent Band Compatibility study to protect GPS users from harmful interference.
So, the list of threats to GPS now includes solar flares, spoofing, jamming, “legal jamming” by Ligado, and the Russian government’s recent threat to destroy GPS satellites. Modernizing GPS must proceed hand-in-hand with protecting it.
Raytheon plans to deliver the final phase of the GPS Ground Control System (OCX) upgrade to the United States Air Force by June 2021, despite past delays to the program.
A report by the General Accountability Office (GAO), issued in May, said the Air Force has yet to develop full cost estimates for the new ground system, as well as the user equipment needed to access the expanded capabilities of GPS III.
In the report, the GAO recommended that the Department of Defense (D0D) conduct an independent schedule assessment of the full program schedule at the end of 2019. DOD did not agree with the recommendation.
“OCX delivery, acceptance, and the ready to transition to operations decision will likely be delayed, potentially exceeding the April 2023 threshold date for completing the program,” the GAO report said.
However, Raytheon said Oct. 1 that it had completed software and hardware development and has started testing and integrating the system, keeping it on track to meet its contractual deadline.
In an Oct. 1 Denver Post article, David Wajsgras, president of Raytheon’s Intelligence, Information and Services business, said Raytheon has changed its process for the OCX upgrade by adopting less-traditional tech startup development processes.
The new process —now in action at Raytheon’s Aurora, Colorado, campus — emphasizes collaboration across teams and has a less linear structure.
“I’d call it almost a 180 from the way we had developed software in the past, from the traditional way for the Department of Defense,” Wajsgras told the Post.
“A few years ago the GPS OCX program was considered the No.1 problem program in the entire Department of Defense,” Wajsgras acknowledged. “Our team truly stepped up to the challenge of what needed to be done in order to get one of the most important programs for U.S. government back on track.”
DOD’s Defense Digital Service helped the company apply an “agile” approach to “DevOps” (development and operations) that stresses collaboration across teams as well as flexibility.
The new process includes “dojos,” centers for focused, quick training, and “hives,” open workspaces without cubicle walls.
Program enters integration and test phase on track to 2021 delivery
Raytheon Company’s GPS Next-Generation Operational Control System, known as GPS OCX, has completed full software and hardware development and entered the system integration and test phase. The milestone keeps GPS OCX, the enhanced ground control segment of a U.S. Air Force-led effort to modernize America’s GPS system, on track to meet its June 2021 contractual delivery deadline.
“GPS OCX is one of the largest, most complex software development programs in the Department of Defense, and we’re now in the home stretch toward full system delivery,” said Dave Wajsgras, president of Raytheon’s Intelligence, Information and Services business.
The GPS OCX team completed development of 1.5 million lines of software code, supported by a pivot to leading-edge commercial software development processes that began in 2016. Additionally, the team’s information assurance best practices helped the program achieve the highest level of cybersecurity protections of any DoD space system.
The U.S. Air Force used the cybersecure GPS OCX launch and checkout system, often referred to as Block 0, to launch the first modernized GPS III satellite into space in December 2018 and the second in August 2019.
The team’s focus for the remainder of 2019 is the delivery of the system’s new modernized receivers, which will measure and monitor legacy military and civilian signals sent by the current GPS satellite constellation plus the new signals sent by the next-generation GPS IIIs.
Ground antenna at Schriever Air Force Base, home of the 50th Space Wing. (Photo: Raytheon)
GPS OCX will maneuver satellite into final orbit over 10 days
The U.S. Air Force used Raytheon Company’s GPS Next-Generation Operational Control System, known as GPS OCX, to support the launch of its second GPS III satellite into space. The ground system will now spend 10 days maneuvering the satellite into its final orbit, demonstrating GPS OCX’s ability to simultaneously support multiple GPS III spacecraft on-orbit throughout the checkout and calibration process.
Raytheon’s GPS OCX has obtained the highest level of cybersecurity protections of any Department of Defense space system.
“GPS OCX performed extremely well during the first launch and has exceeded performance requirements in the months since,” said Dave Wajsgras, president of Raytheon Intelligence, Information and Services. “The team was well-prepared for this launch, and we’re confident the system’s performance will continue to be positive.”
GPS OCX, the enhanced ground control segment of America’s GPS system, has achieved the highest level of cybersecurity protections of any Department of Defense space system. Its open architecture design allows it to integrate advanced protections as they become available, and the system’s industry-leading cyber protections are why it will be used to support all future GPS III launches and GPS constellation operations upon operational acceptance.
Earlier this year, the team completed final qualification testing of the system’s modernized monitor station receivers, which can receive and decrypt all GPS III military and civil signals. Global installation of the receivers starts next month and keeps the program on track for full system delivery by the program’s June 2021 contractual deadline.
In addition to GPS OCX’s role, RGNext, a joint venture between Raytheon and General Dynamics Information Technology, provided operational launch support to ensure the safe launch of the United Launch Alliance’s Delta-IV rocket that was carrying the GPS III satellite. RGNext operates the launch range on behalf of the U.S. Air Force, providing maintenance, range safety, weather monitoring, communication and surveillance support for all launches conducted by defense, civil and commercial companies at the range. To access our press kit, which includes photos, videos and an animation, please visit us here. To learn more about the program’s progress and additional capabilities, visit us here.
Harris Corporation has received a $243 million contract from Lockheed Martin to provide fully digital navigation signals for the first two GPS III Follow-On (GPS IIIF) satellites — to deliver stronger signals, with greater operational flexibility.
Harris’ GPS IIIF fully-digital Mission Data Unit (MDU), the heart of the satellite’s navigation payload which generates the GPS signals, will provide more powerful signals, assure flawless clock operations for GPS users, and add flexibility to adapt to advances in GPS technology, as well as future changes in mission needs.
It will provide improved capabilities over Harris’ 70-percent-digital MDU used for GPS III Space Vehicles 01-10 (GPS III SV01-10).
The new MDU also offers the Air Force a smooth transition to its GPS OCX ground control segment. Harris will seamlessly port its digital signal design, minimizing both integration risks and associated costs.
In September 2018, the U.S. Air Force selected Lockheed Martin, with Harris as its navigation signal partner, to build up to 22 GPS IIIF satellites, with a total estimated contract value up to $7.2 billion.
The Air Force expects the first GPS IIIF satellite, SV11, to be available for launch in 2026.
Launched aboard GPS III SV01 in December 2018, Harris’ first GPS III navigation payload began broadcasting navigation signals on January 8. While testing of the first-of-its-kind satellite continues, the payload has performed beyond expectations.
Harris has provided navigation technology for every U.S. GPS satellite ever launched, enabling the reliable GPS signal that millions of people — including U.S. soldiers — and billions of dollars in commerce depend on every day.
Photo: U.S. Air Force / Staff Sgt. Scott H. Spitzer
Much development has been necessary to enable the new M-code capability on more than 700 weapon systems that require it. This article overviews M-code, the updates to antenna and receiver technology to make these varied platforms M-code ready, and perspectives from key stakeholders in the M-code community.
December 23, 2018, marked an important milestone for GPS. The successful launch of satellite USA-289 represented a key success in what has been a monumentally expensive government program, beset by delays and overspends.
The launch of the first GPS Block III satellite, the first that can provide the full military M-code capability, effectively commenced the physical roll-out of modern M-code hardware.
Ground Control. As far as the space segment is concerned, M-code is finally underway. What about the ground segment? The next-generation GPS operational control system, GPS OCX, is essential for use of the full capabilities of the new Block III satellites. It has been under development for some time.
OCX has drawn Congressional criticism and correlative media attention, but recent reports have been more positive. Since the Nunn-McCurdy breach of 2016, when the project’s future hung in the balance, accounts have grown gradually optimistic. Budget and schedule were re-baselined, and contractor Raytheon’s corrective actions generated results. In the fall of 2017 the Air Force took delivery of OCX Block 0, marking a significant milestone. Block 0, also known as the Launch and Checkout System (LCS), demonstrated compliance with contractual requirements and was accepted by the Air Force.
In spring 2018, Block 0 underwent a series of cybersecurity tests and passed, validating the security architecture of the system. All this puts Raytheon on track to deliver OCX Block 1 in 2021, providing full operational capability. Block 1 and Block 2 are intended to be delivered together, adding operational control of the modernized satellites and signals, including L1C and the modernized M-code.
“There have been no schedule slips with the GPS OCX program since 2017, and the GPS III launch last December was clear proof of our progress,” stated Dave Wajsgras, president of Raytheon’s Intelligence, Information and Services business. “We will continue to meet all of our commitments, and importantly, we will meet our June 2021 contractual deadline.”
Col. Steve Whitney of the GPS Directorate wrote in this magazine in December 2018 that “The journey over the past few years has been challenging, but we have emerged stronger, armed with better metrics, and a culture of integrated development (often called DevOps) which puts us on a path to success. There will be challenges and risks in the path ahead but rather than mountains to climb, I see these more as standard blocking and tackling of a software-intensive program.”
Meanwhile. The Air Force plans to deploy M-code capability in 2020, and OCX seems unlikely to be ready. For this reason, Lockheed Martin was awarded a contract to modernize the existing ground infrastructure as a “gap filler.”
The GPS Control Segment Sustainment II (GCS II) contract was awarded on Dec. 21, 2018, and is worth $462 million. GCS II will support operational capability of M-code in 2020, and continues until 2025, and so there will be a period of overlap between GCS II and OCX, essentially providing two options for controlling the new GPS III constellation. In one view, the Air Force is backing two horses to improve chance of winning: OCX the preferred solution, with GCS II almost like an insurance policy.
With the GPS III ground and space segments looking relatively healthy, attention turns again to the user segment.
WHY M-CODE?
Until now, the military has used the classic P(Y) signal: a binary phase shift keying (BPSK)-modulated encrypted wideband signal. It offers both greater accuracy and increased jamming resistance when compared to the civilian C/A code still employed by the vast majority of GPS receivers.
But the P(Y) code has its drawbacks in the modern world: its wide main lobe sits directly over the top of the C/A code signal (see Figure 1), essentially occupying the same spectrum. When the civilian C/A signal is jammed, the military P(Y) signal is at the very least degraded, if not also jammed itself. It also uses a relatively simple encryption scheme that does not meet today’s cyber security requirements.
Figure 1. C/A, P(Y), and M-Code signal power spectra. (Graphics: Mike Jones)
The M-code signal, on the other hand, is the first military GPS signal to use the BOC modulation scheme. BOC modulation gives signals their distinctive two-lobe appearance, spreading the signal’s energy away from the band center.
The wide spacing of the two sidebands separates the M-code signal from the civilian signals (the legacy C/A signal or the new L1C signal on the L1 frequency, and the L2C signal on the L2 frequency).
Amongst other things, this allows the military to jam the civilian codes without noticeably degrading the M-code signal. Often referred to as blue force electronic attack (BFEA), this is essentially a new facet to navigation warfare (NAVWAR), where enemy use of GPS can be denied whilst allowing friendly forces to continue using it.
The wider occupied bandwidth and increased signal power also help to make M-code more resistant to jamming. M-code also makes use of more modern and flexible encryption methods, ensuring it will be secure and safer from threats such as spoofing attacks.
Scepticism. Defense programs are known for their long procurement cycles, but even by these standards, M-code has taken an extremely long time to get where it is today. Given the enormous cost of the program, and the fact that there is still, as yet, no operational benefit to show from it, many people have questioned its worth. At the time it was conceived it represented a dramatic step forward in military capability but, because it has been so long in development, its operational benefit is becoming diluted.
When M-code was conceived, GPS was still the only operational GNSS in town: everybody had to use GPS — or nothing. Today, the picture differs greatly. During M-code’s insanely slow progress, other GNSS systems have come along, offering their own encrypted signals of a similar ilk. Looking at Figure 2, M-code no longer appears as special as it once was. Its BOC(10,5) signal sits inside the main lobes of Europe’s Galileo PRS signal, which uses a BOC(15,2.5) scheme, and China’s Beidou B1A signal using BOC(14,2).
Figure 2. GNSS encrypted signals around the L1 frequency. (Graphics: Mike Jones)
If you were China, you might consider jamming the central 24 MHz of the L1 band, taking out M-code, whilst still having an operational military service for yourself. Or if you were Russia, you might jam 34 MHz of bandwidth, taking out the US, Chinese, and European systems, whilst still having your GLONASS L1SC military service to use. The situation is more complex than that, of course: each service has the potential to increase signal power in times of conflict, and there is more than one frequency that can be used. But it does demonstrate the essence of the problem: The modern battlespace has moved on, and M-code hasn’t.
CHALLENGES OF RECEIVER DESIGN
Figure 3. C/A code ACF.
With complex signals come complex receivers, and there several headaches when it comes to M-code receiver design. The first is the nature of the BOC signal itself, which has a complex correlation function. Consider Figure 3, which shows the autocorrelation function (ACF) of the traditional civilian C/A code signal. The single peak of the function makes acquisition and tracking a simple process; traditionally early, prompt and late (E,P,L) correlator arms can be used in the tracking process.
Figure 4. L1Cd ACF.
The newer BOC-type signals have a more complex ACF. Figure 4 shows the ACF of the new L1Cd civilian GPS signal, which uses a form of BOS(1,1) modulation. In addition to the main lobe, there are now two side lobes. Receivers must be careful not to lock on to one of the side lobes instead of the main lobe: the receiver architecture starts to become a little more complex.
Figure 5. M-code ACF.
Now consider the ACF of the M-code signal, shown in Figure 5. Like other high-order BOC-type signals, M-code exhibits multiple lobes in the ACF, making robust acquisition and tracking a far more troublesome process. Furthermore, the high bandwidths require high sample rates, which lead to higher power consumption in the hardware.
Another major headache associated with M-code receivers is, of course, the encryption process. Not because encryption is difficult, but again because of the power consumption implications. Consider that each GPS receiver needs to run an encryption engine instance, for each satellite it might wish to receive. Running a high-grade encryption algorithm at a high chipping rate, for a dozen satellites, is a power-consuming process. For dismounted soldiers with limited battery capacity, this is a big deal.
Some people argue that the high-grade encryption process for M-code is too complex. Consider why we want to encrypt a GNSS signal in the first place: firstly to prevent someone from spoofing our signal, and secondly to prevent unauthorised users from using the service. Given that the encryption keys are rolled regularly, how much does it matter if an adversary manages to compromise the encryption? This isn’t a communications security problem: we are not talking about loss of classified information, so there’s an argument that a simpler, less power-hungry form of encryption might have been used instead.
ANTI-JAM ANTENNA COMPATIBILITY
Although M-code offers a certain level of jamming resistance, it is still vulnerable to attacks. As a signal it might have a bit more power, and a bit more bandwidth, than some other signals. But it is, after all, still a GNSS signal, and it can be jammed by an adversary. Where an operational threat analysis indicates that an increased level of jamming resistance is required, then M-code receivers need to be integrated with anti-jam antennas.
Anti-jam antennas, usually referred to in the GNSS community as controlled reception pattern antennas (CRPAs), have been the anti-jam tool of choice for several decades now. I overviewed these in an April 2017 newsletter column. CRPA manufacturers have had to ensure that their products are “M-code ready,” such that they can be seamlessly attached to M-code receivers as and when they appear.
This hasn’t been a recent process: as far back as 2002, the GAS-1 antenna (Raytheon) underwent a series of qualification tests to ensure compliance with M-code. Around 2005, the ADAP antenna (also Raytheon) was launched with a host of M-code features — again an illustration of just how slow the M-code program has moved, given that other technology has been “M-code ready” for 10 or 15 years already.
What’s involved in making a CRPA M-code compatible? Firstly the increased bandwidth: the antenna electronics must digitize the wider bandwidths. Along with the wider bandwidth comes new filtering shapes to ensure optimum performance.
Space-time adaptive processing (STAP) and space-frequency adaptive processing (SFAP) techniques potentially require more taps to ensure high null depths can be maintained across the full bandwidth. The increased power of the M-code signal, particularly if features like spot beam are used, presents another complication to CRPAs: they must not treat the high-power satellite signals as jammers, and try to remove them.
Testing CRPAs presents a challenge to manufacturers: how do you prove that your antenna doesn’t corrupt the M-code signal, when there’s no M-code signal to test it with? To work around this issue, pseudo M-code signals have been used for testing, where representative BOC(10,5) signals without the real encryption are passed through the CRPA and examined for distortion.
RECEIVER DEVELOPMENT STATUS
Due to the security considerations surrounding M-code, only three US organizations are authorized to produce modules: Collins Aerospace, Raytheon and L3. Here are the answers from Collins Aerospace and L3, the answers from Raytheon will appear in later issue.
What are the technical challenges associated with developing an M-code receiver?
Collins Aerospace. The Collins Aerospace Modernized GPS User Equipment (MGUE) Increment 1 development like the SAASM PPS receiver developments faced very challenging technical requirements to support our war fighter needs in an ever-evolving threat environment. Like other complex developments the challenges are initially technical and then transition to integration/test and certification. On the technical front optimizing receiver performance balanced against power consumption are always at the forefront. In addition, it is important to maximize backwards compatibility so as to minimize downstream integration costs while adding an entirely new signal that runs in parallel to the existing system. Collins Aerospace is pleased with the technical development and are actively supporting the integration with both receivers and technical support.
To date, we have delivered more than 770 MGUE receivers to the Air Force to support Air Force, lead platform and DoD-wide Integration and test. Soon the total will grow to nearly 1,100 receivers to support expanded integration and test following the completion of Collins Aerospace security certification.
L3. M-code GPS User Equipment (MGUE) technologies exist today.L3’s Ground Based GPS Receiver Application Module – Modernized (GB-GRAM-M) is a fully-functioning unit that is currently baselined and undergoing an independent Technical Requirements Verification (TRV) by the GPS Directorate.During TRV, each requirement from the Technical Requirements Document (TRD) is independently evaluated for compliance. Upon completion of the TRV, the design is baselined with complete documentation enabling platforms and prime equipment to integrate from a known baseline with low risk. Following integration, operational testing can start immediately to support fielding when M-Code Early Use (MCEU) becomes operational. The TRV of L3’s GB-GRAM-M is planned to be completed by the second quarter of 2019.
L3 resolved numerous technical challenges in developing M-code GPS technologies. The first and ever-present challenge is changing and evolving requirements. Most of these requirement changes are in response to evolving threats that have driven changes into the GPS receiver and/or to higher-level systems. Asan example, the U.S. Army’s Assured PNT (A-PNT) is implementing M- code GPS along with external sensors to establish and maintain an assured solution even in GPS-challenged environments. Other challenging requirements include meeting the security requirements, implementing and testing anti-spoofing algorithms, and ensuring backward compatibility with legacy receivers.
What are the intended platforms for your MGUE?
Collins Aerospace. The Collins Aerospace MGUE receivers are intended to support all warfighter domains: ground, airborne, maritime and munitions to support compliance with Public Law 111-383 SEC. 913 issued in Fiscal Year 2011. Per this directive, M-code is intended for all DoD applications with the exception of passenger vehicles or commercial vehicles with GPS installed. Now that the satellite and control segments of the capability are coming on line, we are working diligently to ensure that user equipment is available for all domains.
L3. L3 has products to meet current market demand. Under the MGUE program, L3 developed a GB-GRAM-M, which is a standard Modular Open Systems Architecture (MOSA) design. The GB-GRAM-M is designed to fulfill retrofit replacements of SAASM receivers, as well as being a primary component of A-PNT systems. L3’s M2GRAM ASIC is the core of our receiver, a GPS module that incorporates signal processing, cryptography, and positioning, velocity, and timing (PVT) processing. The M2GRAM ASIC is capable of being implemented in other form factors for applications beyond ground-based applications. As an example, the M2GRAM is implemented in a GPS receiver specifically designed for Precision Guided Munitions (PGM) applications and was used in a gun launched, guide-to-target demonstration operating as a PGM receiver.
L3 is also augmenting the GPS receiver through the integration of several other technologies, including controlled reception pattern antennas with digital antenna electronics, inertial systems and external sensors, and GPS-denied capabilities. M-code technologies are being implemented in Mounted A-PNT Systems (MAPS), Dismounted A-PNT Systems (DAPS), and handheld systems to bring capabilities to the warfighter.
What is the expected timeline for your MGUE development, acceptance testing, and delivery?
Defense Advanced GPs Receiver (DAGR) from Collins Aerospace, equipping infantry and other warfighters. (Photo: Collins Aerospace)
Collins Aerospace. The Collins Aerospace receivers are supporting ongoing DoD integration and test and our MGUE Increment 1 program is aligned with the Air Force GPS Enterprise roadmap. Ultimately, the Department of Defense (DoD) M-code programs will set the production delivery schedules.
We anticipate that the M-code production ramp-up and continued SAASM PPS receiver production will have a production overlap. Our Collins Aerospace in-house PPS GPS receiver manufacturing capability is ready to support the DoD demand for both M-code and SAASM. Collins Aerospace is fully committed to manufacturing Increment 1 M-code receivers to meet the warfighter’s needs across Airborne, Weapons and Ground, we know the transition from SAASM to M-code will take years. Therefore, Collins Aerospace will continue to manufacture SAASM receivers for years to come as the International MOD Policy for M-code use is still being formulated.
L3. L3’s GB-GRAM-M is now available. L3 received security certification and approval in 2016 and TRV is planned for completion in the second quarter of 2019. With TRV, L3 is receiving a new security certification and approval of the latest receiver update. Government agencies, prime contractors and laboratories can order GB-GRAM-M now with delivery in the fourth quarter of 2019.
What does testing and verification process involve?
Collins Aerospace. As with any Precise Positioning Service (PPS) GPS development, the testing involves functional verification of the receiver in a wide variety challenging of environmental, thermal, electromagnetic interference/ high-intensity radiated field (EMI/HIRF) environments. Collins Aerospace is leveraging proven test and verification approaches founded upon our long history of successful product introductions and field performance. As this is a PPS receiver it is also essential the receiver design comply with the government’s required Security Approval process.
L3. The testing and verification of L3’s GB-GRAM-M included internal testing and independent testing through the GPS Directorate’s TRV process. Further risk reduction testing within the MGUE program is planned as Phase IV testing where the GB-GRAM-M is integrated into a lead platform for the U.S. Army and a lead platform for the U. S. Marine Corps. An operational assessment is performed on both lead platforms to assure common problems associated with integration and operational testing are addressed prior to implementing M-Code GPS Receivers across all of the platforms.
Will the MGUE be compatible with CRPA anti-jam antennas; are there any special considerations for this?
Collins Aerospace. The Collins Aerospace product family includes our Digital Integrated Anti Jam Receiver (DIGAR) product family that leverages CRPA anti-jam antennas for enhanced anti-jam (AJ) performance. Our DIGAR AJ technology enhances the performance with fixed reception pattern antenna (FRPA), CRPA and is compatible with all PPS waveforms. Regarding the interfaces between the receiver and the anti-jam antenna electronics, a GPS receiver with a standard RF interface is compatible with a CRPA in nulling mode and FRPA antennas. Advanced capabilities such as beamforming/beamsteering require tight coordination and additional interface with the GPS receiver.
L3. The GB-GRAM-M is designed to operate with a fixed reception pattern antenna (FRPA). A CRPA antenna using digital antenna electronics to generate signals matching the characteristics of a FRPA is fully compatible with the GB-GRAM-M. With a higher level of integration of a GPS receiver and a CRPA, the system capabilities are greatly enhanced. L3 has performed this integration and can perform advanced capabilities such as angle of arrival and beamforming using M2GRAM, digital antenna electronics, and CRPA technologies. These capabilities can be found in L3’s Mounted Assured PNT System (MAPS) and Anti-Jam Antenna System (AJAS) products.
Army Stryker ground combat vehicle. (Photo: Karolis Kavolelis / Shutterstock.com)
OPERATIONAL DEPLOYMENT
The U.S. Air Force GPS Directorate provided answers to the following questions regarding MGUE.
Which platforms will be equipped with M-code-capable MGUE, and how many of each?
GPS Directorate. The Air Force is developing M-code-capable GPS receivers under the MGUE Increment 1 program. The receivers in development will be provided to four service-specific lead platforms for integration, developmental, and operational testing. Lead platforms are:
the Army Stryker ground combat vehicle,
the Air Force B-2 Spirit bomber,
the Marine Corps Joint Light Tactical Vehicle (JLTV),
and the Navy Arleigh-Burke class destroyer (DDG).
Following the lead platform efforts, procurement of M-code-capable GPS receivers will be decided by the Services and executed by individual platforms and programs.
What are the timelines for rolling out M-code on these platforms?
GPS Directorate. Early integration and test activities have already begun for each MGUE lead platform. Operational testing is expected to begin in 2020 and complete in 2021, which is a key activity to enable the fielding of M-code-capable systems.
B-2 Spirit multi-role bomber capable of delivering both conventional and nuclear munitions. In December 2017, the Air Force completed a series of successful flight tests of M-code GPS using a Raytheon Company receiver on board a B-2 Spirit at Edwards Air Force Base, California. (Photo: U.S. Air Force/Bobby Garcia)
What advantages will M-code bring, over existing military GPS receivers?
GPS Directorate. Modernized GPS receiver cards under development with the Air Force MGUE Increment 1 program will enable the use of M-code and provide U.S. forces with enhanced position, navigation, and timing capabilities, in addition to improving resistance to threats, such as jamming efforts by adversaries.
How will keys and key distribution be managed?
GPS Directorate. None of this is publically releasable.
Will M-code be made available to other friendly nations? If so, how is this managed?
GPS Directorate. The current policy allows for the sale of M-code equipment to all 57 authorized GPS PPS nations. The M-code technology will be made available to these nations through the Foreign Military Sales process.
USER PERSPECTIVE
The Department of Defense supplied answers to the following questions for users and warfighters.
What are the benefits you perceive will come from new M-code GPS equipment?
DoD. Provides U.S. forces with enhanced position, navigation, and timing capabilities, in addition to improving resistance to threats, such as jamming efforts by adversaries.
Will it change how you perform military operations, or enable any new ones?
DoD. Modernized GPS receivers provide the next-generation GPS capabilities to the warfighter. Operational testing will enable the services to determine operational utility of MGUE. It will ensure our soldiers, sailors, airmen, and marines have the ability to get in, accomplish their mission, and get home accurately.
How will M-code-based GPS receivers be brought into operational service? Will there be a mass upgrade of assets, or a phased introduction?
DoD. Procurement of M-code-capable GPS receivers will be decided by the Services and executed by individual platforms and programs.
Elsewhere in this (January) issue you’ll find the hard facts — basic, but hard — concerning the inaugural launch of the long-awaited GPS III constellation. On pages 10 and 12, with some seasoned leavening between, on page 11.
This column instead waxes briefly on the phenomenon of time, and humankind’s struggle to dominate it, to subject the fourth dimension to its own will.
For GPS III has been, yes, long awaited, long debated, long victim to multiple delays of many colors and causes, scrutable and inscrutable, of technological challenges and institutional barriers, and of that base determinant, money. The Government Accounting Office has issued its fair and due share of reports pointing alarmed fingers at constellation gaps and fulfillment shortfalls and the trials of OCX, the ground control system without which GPS III satellites may some day, soon or not-soon, be capable of broadcasting powerful new signals from space, yet not able to do so because of lagging accomplishment on Earth.
It’s often said that GPS is a victim of its own success, that older satellites living beyond their forecast lifetimes have allowed the Air Force to economize by not replenishing when unnecessary. There’s wisdom in this, of course.
Were my friend Don Jewell still with us, he would be justifiably proud of the Air Force for launching this new golden era of the gold standard in positioning — yet he would have seethed for years over the continued pushes to the right.
This reminds me a good deal of the drama and occasional comedy in the rise of Galileo, observed from afar. Next month I’ll give a talk at the European Space Agency, provisionally titled “An Outside History of Galileo,” the bemused viewpoint of one who only heard and interpreted the news, but did not participate in its forming.
For such complex endeavors do not happen easily or speedily or exactly as planned by mere mortals. Nor should they. Despite much gnashing of teeth, no one — in the civil sphere at least — has suffered unduly from the longish delays in either satnav system’s modernization. Perhaps a few lives could have been saved in the military, or greater strategic advantage gained, with the new capabilities that III will offer warfighters, had same been available on schedule, say, four to six years ago. But even this is mere conjecture.
There is a rhythm and a flow to life, and we are part of it. You can hurry neither sundown nor sunrise. Things happen in their own due course.
When full GPS III capabilities arrive — I don’t believe 2023 — then it will still be in good time. In its own best time, actually, to be here.
