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GPS architecture modernization: Where we were and where we are headed

December 22, 2023  - By

History of GPSIt may be hard to remember — or imagine — life without the Global Positioning System (GPS). From finding the nearest Dunkin’ Donuts to making ATM withdrawals, GPS is part of everyday life. It makes global finance possible, first responders faster, electric grids smarter and industries more efficient. Without GPS, the critical infrastructure that powers homes and workspaces, mobilizes roads and rails, guides air travel, delivers news and even produces food could come to a grinding halt. That fact is not lost on the United States’ adversaries.

Modernizing GPS to make it work better in times of peace and to ensure its resilience in times of conflict is a prime responsibility of the Space Systems Command (SSC) of the U.S. Space Force (USSF).

History

When it comes to anniversaries, 2023 is a big year for GPS.  It’s widely considered to be the 50-year anniversary of GPS because it was on December 17, 1973, that the Defense Systems Acquisition Review Council (DSARC) gave U.S. Air Force Col. Bradford Parkinson, now retired and hailed as the father of GPS by many in the aeronautics and astronautics sectors, approval to proceed with development of what would become today’s 31-satellite GPS constellation.

It also marks 40 years since President Ronald Reagan authorized the use of GPS for civil aviation following the downing of Korean Air Lines Flight 007, after it inadvertently entered hostile air space. This year is also GPS’s 30-year anniversary of initial operating capability and the 20-year anniversary of the Federal Aviation Administration (FAA) Wide Area Augmentation System (WAAS), which enhances the accuracy and integrity of GPS services across the entire National Airspace System.

At the most recent meeting of the Civil GPS Service Interface Committee, the recognized worldwide forum for effective interaction between civil GPS users and GPS authorities, Parkinson — who, after his service in the U.S. Air Force earned a Ph.D. and has been a professor at Stanford University for decades — recounted his first-hand experience making GPS a reality. The former chief architect for GPS, who led original advocacy for the system as an Air Force colonel, described the incredible challenges and numerous unique innovations involved in starting this program.

Today’s GPS continues to deliver on its commitments for accuracy, integrity, availability, continuity and coverage. It is considered by many the gold standard in navigation and timing. Yet challenges remain, posed by an increasingly contested space domain and emerging threats from pacing challengers and adversarial nations. Advancing, maintaining and modernizing the GPS enterprise for the benefit of commercial, civil and military users falls under the responsibility of SSC and is carried out by the field command’s Military Communications and Positioning, Navigation & Timing program executive office (SSC/MilComm & PNT), in collaboration with its exceptional mission partners, and launch services provided by SSC’s Assured Access to Space program executive office.

As we celebrate the multiple GPS anniversaries, it is worth exploring successes in GPS modernization. This update will explore the exciting advancements in the GPS space systems, user equipment, and control systems.

Space Systems

On January 18, the Lockheed Martin GPS III Space Vehicle 6 (SV06) launched into orbit aboard the SpaceX Falcon 9 Block 5 rocket out of Cape Canaveral, Florida. The successful launch of SV06 and handoff to the USSF’s Space Operations Command/Space Delta 8/2nd Space Operations Squadron marked another key step in the larger goal of modernizing the GPS constellation. SV06 is the sixth GPS III satellite to be launched and is equipped with the full suite of modernized signals and capabilities. The GPS III satellites are more capable and resilient than their predecessors. Improvements include three times greater accuracy and up to eight times improved anti-jamming capabilities.

In preparation for future launches, the GPS III team has been diligently working with the Assured Access to Space Launch Enterprise to ensure rigorous and successful integration of the GPS III spacecraft’s launch systems onto a brand-new rocket, the United Launch Alliance Vulcan Launch Vehicle. GPS III SV07/Vulcan is targeted for launch in the summer of 2024.

Additionally, production of the tenth and final space vehicle in the GPS III fleet was finalized this year and it has a target launch date of 2026. GPS III Space Vehicles 7-10 are in storage and available for launch, awaiting launch call-up.

The modernization, however, doesn’t end there. GPS IIIF continued to make progress this year with development and integration of the follow-on spacecraft program with 10 vehicles now in production. GPS IIIF Non-Flight Satellite Testbed completed panel integration and initial system performance testing and the program completed an integrated baseline review. The GPS IIIF team worked with the National Security Agency to successfully complete an information assurance preliminary design review, one of the first such reviews of its kind. The team has also made essential inputs to the planning for the future GPS IIIF launch and checkout capability.

GPS III Space Vehicle 06 (SV06) was launched Jan. 18 from Cape Canaveral Space Force Station in Florida. It is the 18th GPS satellite to broadcast the L5 signal.

GPS III Space Vehicle 06 (SV06) was launched Jan. 18 from Cape Canaveral Space Force Station in Florida. It is the 18th GPS satellite to broadcast the L5 signal.

User Equipment

SSC/MilComm & PNT actively manages and maintains the public GPS interface specifications that allow industry to build civil receivers that successfully capture and process the GPS signal-in-space satellite-broadcast. Simultaneously, SSC also leads design and development of military receivers, currently the Military GPS User Equipment (MGUE). In April, the MGUE Increment 1 team successfully completed technical requirements verification on its MGUE GPS receiver application module — a standard electronic module specifically designed for aviation and maritime users. This allowed the MGUE Inc 1 program to deliver its new aviation and maritime software to the U.S. Air Force and U.S. Navy to support the lead platform integration and testing on the B-2 Spirit bomber and the Arleigh Burke guided-missile destroyer. This is the first fully functional GPS aviation and maritime software suite to support the jam-resistant military M-code signal.

GPS has an active and successful foreign military sales (FMS) program with 60 allied partners, and many of them are highly engaged with SSC/MilComm & PNT to acquire MGUE receivers with their M-code capabilities. According to the Department of State, U.S. allies and partners purchase approximately $45 billion annually in arms, equipment, and training — many equipped with GPS — via FMS.

This spring, the MGUE Increment 2 team, developing an advanced, follow-on receiver, completed the new Next Generation Application-Specific Integrated Circuit (ASIC), the first of two major Critical Design Reviews (CDRs) with mission partner BAE Systems. That success was followed by a second CDR this summer for the MGUE Increment 2 Miniature Serial Interface (MSI) receiver card, which integrates the Next Generation ASIC along with a host of other innovations. L3Harris, a mission partner, has also successfully completed its own next generation ASIC CDR and is on-track for an MSI CDR in October. MGUE Increment 2 also awarded a Joint Modernized Handheld contract to the Technology Advancement Group, enabling this industry partner to move forward on its MGUE Increment 2 Handheld initiative.

Control Systems

While the current operational control system continues performing at a high level, a major update to the GPS modernization architecture is underway. In March 2022, the USSF began formal testing of the Next Generation Operational Control System (OCX) Block 1/2 system through the Functional Qualification Test designed to test OCX requirements. Currently, preparations are underway to follow that up with a major government-led Integrated Systems Test.

OCX developmental testing is an important part of the software development process. Thorough developmental testing can help ensure that OCX is of high quality and meets all requirements. Testing is rigorous and comprehensive; it is a complex and challenging undertaking, but one necessary to ensure OCX is ready for operational use before it is transitioned into service.  SSC’s program office is taking the necessary steps to ensure that it will be a success.

The OCX 3F program also contributes to SSC’s advancements in GPS control systems. The follow-on to OCX for support to GPS IIIF spacecraft has successfully completed a Critical Capability Release for the GPS IIIF launch and checkout capability.

GPS IIIF

GPS IIF

Sustainment

SSC/MilComm & PNT’s GPS Support Delta has a legacy of providing sustainment expertise for Space Operations Command’s operations team. It sustains a global network including a Master Control Station (MCS), Alternate MCS, 11 command-and-control antennas, and 16 monitoring sites, plus 38 on-orbit GPS spacecraft. The sustainment team performs seamlessly, anticipating issues, collaborating with operators, updating servers and software tools, enhancing cyber secutiry and fine-tuning GPS to keep it running at peak performance.

Future Opportunities

In 2019, the department of the Air Force designated the Navigation Technology Satellite-3 (NTS-3) as a Vanguard program and the Department of Defense’s first experimental integrated navigation satellite system in nearly 50 years. Co-sponsored by SSC and the Air Force Research Laboratory, NTS-3 is helping to pave the way for more robust and resilient positioning, navigation, and timing.

In June, SSC/MilComm & PNT hosted its first Alternate/Augmented PNT Reverse Industry Day at SSC’s new Commercial Space Marketplace for Innovation and Collaboration Center. The event was a unique opportunity for government leaders and technical experts to hear directly from industry in a one-on-one environment about their many exciting innovations and opportunities as well as challenges. SSC was joined by its close government and interagency partners, including representatives from the Department of Transportation, the National Space-Based PNT Coordination Office, the Space Operations Command/Mission Area Team, the Air Force Research Laboratory, and the Space Development Agency. Through the event, SSC gained market intelligence and made many valuable industry connections for future investments.

Conclusion

As the nation celebrates an exciting 50-year anniversary of GPS, continued enhancements in the three elements of the GPS enterprise — space systems, user equipment, and control systems — represent significant milestones toward GPS modernization. This essential upgrade is delivering many new GPS capabilities — including robust new signals such as M-code, L2C, L5, and L1C — while preserving backward compatibility for GPS legacy signal users. GPS modernization will enhance utility, make the system more robust and resilient, and ensure that the United States, its allies, and its government agency partners have access to the most accurate and reliable navigation and timing services available. At the same time, while we continue to look for ways to (in the words of the National Space-Based PNT Advisory Board) “protect, toughen, and augment” GPS capabilities, we are also actively engaged in evaluating ways to incorporate alternate sources of PNT, as well as GPS augmentation, that will continue to make PNT capabilities even more robust and resilient in the future.

About the Author: Michael J. Dunn

Michael J. Dunn works with U.S. Space Systems Command as a Capability Area Integrator for Positioning, Navigation and Timing.