A congressional appropriations panel cast some doubt on whether a U.S. Space Force effort to protect its GPS system from signal jamming will be as resilient as the service hopes.

The Space Force said in February it was considering launching a constellation of small navigation satellites to augment the 31 GPS satellites now in orbit. The premise of the effort, dubbed Resilient GPS, would be to provide an additional layer of capability through a fleet of more affordable and smaller spacecraft.

But the House Appropriations defense subcommittee isn’t sold on the idea that flying more GPS satellites will inherently boost resiliency, and its proposed fiscal 2025 defense spending bill raises questions about the Space Force’s plan.

“While proliferation may provide some advantages, it is not clear how these additional satellites increase the resilience against the primary jamming threat to GPS, compared to alternative concepts for position, navigation, and timing systems being pursued elsewhere in the Department of Defense,” lawmakers said in a report accompanying the bill, released June 12.

The Pentagon has become increasingly concerned about GPS signals — used to guide weapons and help troops navigate difficult terrain — being jammed or spoofed by adversaries. Russia has taken advantage of this vulnerability in Ukraine, using electronic warfare to jam signals on a regular basis.

The Air Force announced in April it would use authority from Congress to shift unused funds from elsewhere in the Space Force’s budget to begin development on Resilient GPS. Those authorities, known as quick-start, were approved in the Fiscal 2024 National Defense Authorization Act and allow the Defense Department to reprogram up to $100 million in funding to start high-priority programs before they are approved as part of a formal budget cycle.

According to the subcommittee, the department has since notified Congress it expects the Resilient GPS program to cost $1 billion over the next five years. To date, the Space Force has repurposed $40 million in fiscal 2023 funding for the effort and, since it didn’t include the program in its FY25 budget, has asked lawmakers to realign another $77 million toward Resilient GPS in that year’s appropriation.

In its proposed bill, the subcommittee denied the service’s request to realign FY25 funding, questioning whether the quick-start process was the best pathway for this effort. Lawmakers note that the service could have requested funding for Resilient GPS as part of its budget submission rather than rely on Congress to approve multiple funding shifts to support the effort.

Further, the subcommittee notes that the program seems to focus on the satellites without addressing how it would alter ground systems and user equipment to improve resilience. The Space Force has said the goal is for the spacecraft to be interoperable with existing user devices.

To shed more light on the viability of the service’s plan, the subcommittee directs the Pentagon’s Cost Assessment and Program Evaluation office to assess whether the effort is the department’s best option for boosting the resiliency of its positioning, navigation and timing capabilities.

Courtney Albon is C4ISRNET’s space and emerging technology reporter. She has covered the U.S. military since 2012, with a focus on the Air Force and Space Force. She has reported on some of the Defense Department’s most significant acquisition, budget and policy challenges.

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