While the Pentagon has undertaken 11 alternatives to GPS efforts, DoD’s Positioning, Navigation and Timing (PNT) Oversight Council has emphasized the envisioned move to the anti-jamming, anti-spoofing, encrypted M-code signal and should prioritize GPS alternatives, according to a Government Accountability Office (GAO) report for the Senate Armed Services Committee this month.

The council, co-chaired by the Pentagon acquisition chief and the vice chairman of the Joint Chiefs of Staff, “has largely prioritized modernizing the existing GPS system over alternative PNT efforts during recent meetings and has no strategic objectives or metrics to measure progress on the alternative efforts,” per the GAO report. “Defined objectives and metrics would help the council better measure overall performance and mitigate any potential gaps in PNT capabilities as the military transitions to using M-code.”

Four of the 11 alternative to GPS efforts are multi-PNT receivers–open systems boxes able to integrate multiple sources of PNT–including GPS M-code, an inertial sensor, and clock–so that military forces may continue a mission even if one PNT source becomes unavailable. Of the four military service multi-PNT receiver programs–two by the U.S. Army, one by the U.S. Navy, and one by the U.S. Air Force–only the Air Force’s Resilient-Embedded Global Positioning System Inertial Navigation System (R-EGI) has a firm business case, GAO said.

In February last year, the Air Force Life Cycle Management Center awarded Huntsville, Ala.-based Integrated Solutions for Systems, Inc. a $95 million contract for Phase 2 of R-EGI, which is to field first aboard F-16 fighters.

“Since the late 1990s, DoD has been developing a new, more robust GPS capability known as military code, or M-code,” the GAO report said. “While M-code is a stronger signal with more advanced encryption, its development has been underway for more than a decade, with initial operational capability still years away.”

In addition, GAO said that the cost to move to M-code “will likely be billions of dollars greater than the $2.5 billion identified through fiscal year 2021, because significant work remains.”

“Additionally, current PNT receivers are not designed to easily add in new sources of PNT information,” the report said. “We reported in 2021 that such PNT receivers are a challenge to fielding new capabilities, as these systems cannot be upgraded affordably.”

In addition to the four multi-PNT receivers, there are seven other alternative to GPS undertakings–the Navy’s Automated Celestial Navigation System (ACNS), PNT Upgrade to the Cooperative Engagement Capability (CEC), and the AN/WSN-12 Inertial Navigation System; the Army’s Alternative Navigation (ALTNAV), and Assured Precision Weapons and Munitions (APWM); the Air Force’s  Navigation Technology Satellite-3 (NTS-3);  and DoD’s critical time dissemination.

DoD, in its response to GAO, said that annual reports by the PNT Oversight Council will keep Congress apprised of the objectives of the council’s alternatives to GPS and how DoD is meeting such goals.

Ensuring U.S. forces face minimal disruption to their mission in areas of GPS interference has been a stated priority for DoD.

The Air Force, for example, began the Radar Aided Targeting System (RATS) effort for the B-2 stealth bomber in 2018, and the service is fielding the Northrop Grumman [NOC] system this year (Defense Daily, July 14).

RATS “significantly improves the ability to accurately employ near-precision weapons without the need for GPS,” Northrop Grumman has said. “RATS is a key element of the B-2 nuclear modernization, as GPS may not be available during a bomber task force mission. RATS will provide north, east, and down offset coordinates to the platform based on the aircrew’s radar designation, requiring only one image per target.”