GPS Modernization: Better Information and Detailed Test Plans Needed for Timely Fielding of Military User Equipment, Report to Congressional Committees [open pdf - 2MB]
From the Highlights: "The Air Force launched the first GPS [Global Positioning System] satellite capable of broadcasting the jam-resistant M-code [military code] signal in 2005. However, delays have plagued the ground and user equipment segments needed to take advantage of the technology. The Senate Report accompanying the National Defense Authorization Act for Fiscal Year 2020 included a provision for GAO [Government Accountability Office] to report on the status of GPS modernization. This report assesses, among other things, the extent to which DOD has identified systems to field with M-code-capable equipment, and its plans for the procurement, installation, and fielding of this equipment."
Government Accountability Office: https://www.gao.gov/