Precision Navigation Systems: Challenges Remain with Fielding New Capabilities

What GAO Found The Department of Defense’s (DOD) efforts to modernize GPS continue to face delays. In response, DOD is developing new complementary sources of positioning, navigation, and timing (PNT) data to mitigate GPS threats. In 2026, after years of delays, DOD canceled the Next Generation Operational Control System ground control system and began modernizing the existing GPS Operational Control Segment. Among other effects, this creates risks for the launch, checkout, and operation of new GPS satellites. Given ongoing threats to GPS, DOD is operating and continuing development of (1) satellite-based PNT systems, (2) non-satellite-based PNT systems, and (3) backup timing solutions. Operational Illustration of Threats to GPS and Complementary Positioning, Navigation, and Timing Systems The Air Force continues to make progress developing modernized GPS military code (M-code) receiver cards, but challenges remain with fielding and integration. For example, the M-code aviation receiver programs continue to encounter development and integration challenges. In response, the Navy is developing an interim solution for its aircraft to use M-code. On the other hand, the Army and Navy are fielding M-code capable and multi-PNT receivers in ground vehicles, ships, and Army aircraft. All the military services are also pursuing integration of complementary PNT data into multi-PNT receivers. Challenges with aligning multiple, fragmented PNT efforts across the military services impact DO