“The Department of Defense’s (DoD) Global Positioning System (GPS) is the principal source of positioning, navigation, and timing (PNT) information for the U.S. military and civilian users. Due to DoD’s reliance on it, GPS also represents a potential single point of failure for DoD. We [the Government Accountability Office (GAO)] previously reported on DoD’s efforts to modernize GPS with a more jam resistant, encrypted, military-specific signal, referred to as military code (M-code), and we found that DoD is years away from fielding this capability after spending more than two decades and billions of dollars.”
That was the opening of a GAO letter sent last Wednesday to Congress accompanying a 58-page report titled PRECISION NAVIGATION SYSTEMS: Challenges Remain with Fielding New Capabilities, which explains the key role that GPS delivery of PNT data plays in this country’s military and civilian activities -- and the need to update the system.
The M-code secure, jam-resistant GPS signal is designed to be used by roughly 700 U.S. weapons systems deployed by Army, Navy, Marine Corps and Space Force services, but because of a limited supply of specialized microchip sets and production bottlenecks of other key elements, some M-code deployments have been pushed back to 2049, according to the GAO.
I will discuss this more below. Meanwhile, the U.S. military services continue to rely on legacy GPS receivers or alternative systems for PNT-guided operations. For example, the GAO report described “non-satellite-based PNT using data derived from internal or external sources of information to sensors, from geophysical sources, or from celestial sources (e.g., inertial measurement units, cameras or terrain sensors, magnetic or gravity sensors, and celestial sensors).”
First, a bit of GPS background and history supplied in part by the GAO.
GPS consists of three segments: a constellation of approximately 31 medium Earth-orbiting satellites, with at least 24 continuously broadcasting their position and time data; a ground control segment – Space Command’s Delta 8 at Schriever Air Force Base, Colo. -- for command and control of the satellite constellation; a user segment, comprising receivers used globally by military and civilians in aircraft, ships, land vehicles, precision-guided munitions, and handheld devices.
The user equipment receives signals from four GPS satellites and, with that transmitted data, instantly calculates the user’s location and precise time.
Although the U.S. Government created and continues to control and maintain GPS, it is freely accessible to anyone with a GPS receiver. There are three other similar global systems: Russia’s GLONASS was developed during the Cold War; the European Union manages Galileo, and China operates the BeiDou Navigation Satellite System.
Today’s U.S. GPS originated in 1973 when the Defense Navigation System, later named NAVSTARS GPS, was approved, primarily to guide ships. In 1978, the first GPS satellite was launched into orbit, with the full satellite complement not reaching initial operational capability until 1993. By then, it had been made available for civilian use as well as military, a decision made by President Reagan in 1983 after the Russian downing of Korean Air Lines Flight 007.
By the 1991 Persian Gulf War, the GAO report said, “GPS equipment was small and inexpensive enough to also be used on aircraft and other military vehicles. Since then, further advances, such as the development of even smaller microchip-sized receivers, have allowed GPS to provide precise PNT information for individual soldiers, munitions, smaller weapons technology applications, and civilian applications, like smart phones.”
Meanwhile, according to the GAO report, “GPS signals are being actively targeted by adversaries who seek to disrupt or deny GPS to U.S. warfighters. These threats include (1) jamming, (2) spoofing, (3) cyber, and (4) direct attacks on satellites or satellite infrastructure.”
DoD is mitigating jamming attacks “by installing specialized antennae -- referred to as controlled reception pattern antennae (CRPA) -- on weapon systems and munitions,” according to the GAO report, which added, “These antennae provide the ability to identify and filter out the jamming signals.”
Spoofing is being dealt with “in part by developing and installing receivers with M-code capability, which will provide more secure encryption,” the report said. As for cyberattacks, DoD is “ensuring that computer systems and networks are protected against cyber attacks that can target satellites and their associated ground control systems,” according to the GAO.
Since 2000, the Air Force -- and later the Space Force – have pursued a multibillion-dollar effort to modernize the existing GPS capability. The modernization effort included adding the more robust and more securely encrypted GPS military signal capability, known as M-code. It also included: 1) satellites that broadcast the M-code signal, 2) a ground system that controls both the existing and new M-code GPS satellites, and 3) user equipment to receive the M-code signals.
The first satellites capable of broadcasting M-code have been on orbit since 2005, with upgraded versions referred to as GPS III.
The launch of the GPS III third generation of 24 M-code satellites was completed on April 21 of this year, providing eight times the anti-jamming capability and four times the accuracy of previous iterations. “The next generation of satellites, known as GPS III Follow-on, or GPS IIIF, are in production by Lockheed Martin, and will begin launching as early as 2028,” according to a Space Systems Command press release.
However, it’s a different story with the new generation ground system, referred to as Next Generation Operational Control System (OCX). It began development in 2010 and was supposed to achieve transition to operations by June 2017. Instead, there were numerous technical problems and protracted delays. Costs rose from $3.7 billion to almost $7 billion or more, and in April 2026, DoD directed the Air Force to formally terminate the OCX program, according to the GAO report.
Despite the cancellation of the OCX program, then-Chief of Space Operations Gen. Chance Saltzman said in April the new ground control system needs to be prepared to support future GPS satellites, including GPS IIIF and beyond.
However, despite the OCX problems, the Space Force has been making upgrades to the existing GPS ground control segment through Lockheed Martin. Last week, an Air and Space Forces Magazine daily report said, “Since April, the Space Force has awarded Lockheed an additional $199 million…to support launch and command and control for GPS IIIF satellites…and to begin a full technology refresh of the GPS ground segment hardware and software.”
The final problems harming total GPS modernization – including delays and mounting costs – are best portrayed in the GAO report’s description of the military services’ development and procurement of separate receivers for the M-code data.
While development of the M-code-capable receiver cards has been led by the Space Force and Air Force, the eventual fielding of receivers to specific operational platforms, such as weapons, has remained the responsibility of the individual services.
According to the GAO report, “Currently, there are more than 50 priority weapon systems [considered in the GPS modernization programs]. The largest numbers of priority weapon systems are in munitions and aviation systems. The Navy has the highest number of systems, followed by the Army…Priorities for M-code modernization take into account the needs of the specific classified operational scenario as well as the expected life spans of the weapon systems involved. Weapon systems that are expected to no longer be in use around or before 2030 are not priority weapon systems.”
Congress mandated the PNT Oversight Council in the Fiscal Year 2016 National Defense Authorization Act, and DoD established it with the mission of overseeing the department’s GPS modernization portfolio.
However, as the GAO report explains, “Budget authority for key aspects of DoD’s PNT efforts remains under the control of the [separate military] services. This budgetary fragmentation complicates efforts to align interdependent PNT capability development and fielding efforts to ensure timely delivery to the warfighter.”
For example, the GAO found that despite recommendations from the PNT Oversight Council concerning inadequate Air Force funding for aviation receiver programs, “chronic underfunding” continued and the Air Force aviation receiver programs did not meet their development goals on their expected timelines.
“Pursuing modernized GPS and complementary PNT technologies to augment GPS,” the GAO report concludes at one point, “requires foresight and planning. Integration timelines for weapon systems are often lengthy, and schedules must be properly aligned for the development of such modernized PNT technologies and their integration into weapon systems. Additionally, these timelines for integrating new PNT technologies can be further complicated by the interdependence of systems. For example, the military services will likely upgrade some munitions to use M-code before the capability is integrated into weapon systems that fire those munitions.”
Since, as the GAO points out, the GPS system “is vast and touches almost all vehicles, ships, aircraft, precision-guided munitions, and dismounted personnel within the [Defense] Department,” I would say more DoD attention needs to be paid to getting this modernization back on track.
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