A plan by America's Space Force to harden GPS against spoofing attacks may be going nowhere: A request by the service branch for $77 million of public cash to finish the work is struggling to get approval from Congress.

The US Department of Defense's overall proposed budget for 2025, which is now being pulled apart and scrutinized by the House Appropriations Committee, included the aforementioned request for the USSF's Resilient GPS (R-GPS) project, initial work for which began this year.

Don't confuse R-GPS with a technical concept - it's not a new type of signal or something like that - and it looks more like the Space Force just wants to lob mini-satellites into orbit to augment the GPS constellation and make it more robust to spoofing. The $77 million being asked for is less than the purchase cost of a single F-35 fighter.

According to the Appropriations Committee's report on the Pentagon's proposed budget, released on Wednesday in anticipation of Thursday's markup hearing, R-GPS "purports to provide greater resilience by proliferating a constellation of about 20 small satellites transmitting core GPS signals." 

Space Force has already been doing some work on R-GPS, thanks to the Air Force's Quick Start initiative, approved for the current fiscal year's budget, that allowed the two military branches to proceed with early engineering and design activities for the project. R-GPS was granted $40 million of repurposed funds in April to get underway as part of a quick start program.

The House committee isn't sure more satellites equates to more resilient GPS, however - especially with a price tag of $77 million this year and an estimated $1 billion over five years. 

"While proliferation may provide some advantages, it is not clear how these additional satellites increase the resilience against the primary jamming threat to GPS," the committee noted. 

GPS jamming has become a serious concern, especially for commercial air travel in Europe and the Middle East - and the committee seems to think taxpayer money may be better spent on a new global positioning alternative.

Speaking of jam-proof geolocation, that brings up the committee's second concern: Even with the advent of jam-resistant M-code signals that would be used in new GPS satellites (and are broadcast from some existing ones, too), more satellites "does not address longstanding issues with the lack of M-code GPS user equipment," the committee said. 

GPS users without access to M-code compatible ground equipment includes [PDF] the US military, whose hardware has faced repeated delays and is now unlikely to be ready before the middle of next year.

Those things considered, "The committee recommendation does not include the requested $77 million," the report said - and it only gets worse for the USSF's R-GPS dreams from there.

In addition to not backing the R-GPS budget request, the committee also thinks now is the perfect time to take a closer look at the entire concept to see whether it's a worthwhile approach.

The budget report gives the Director of Cost Assessment and Program Evaluation 180 days from the passage of the DoD's Defense Appropriations Act to hand over a report "that includes an assessment of whether R-GPS is the best alternative to improve the resiliency of position, navigation and timing services to support national security." 

The bill is in its markup committee hearing today, and it's not clear when a final version - with or without the Space Force's $77M R-GPS included - will be available. We note that the agency's 2025 budget request also includes [PDF] other GPS resiliency work, including anti-jamming tech development, equipment upgrades and improved cybersecurity for ground units. ®

https://www.theregister.com//2024/06/13/space_force_gps/