Members of the House and Senate have sent letters to the Federal Communications Commission, asking the agency to take a closer look at potential interference from the LightSquared network.

Additionally, the House Agriculture Committee this month included language in an annual agriculture appropriations bill acknowledging potential threats to GPS used by farmers, rescue workers, and forest firefighters to the FY2012 Agriculture Appropriations bill. The language goes on to direct the U.S. Department of Agriculture "to ensure the FCC is aware of these concerns and to work with other Federal agencies, such as the Department of Defense and the Department of Transportation, to address them."

"We greatly appreciate these strong congressional expressions of interest and concern about the safety and efficiency of the GPS network and the potential impacts of LightSquared on the nation’s GPS safety and security infrastructure," Bolen's testimony said.

Concerns about GPS interference have also been raised on a global stage. In a June 13 letter to U.S. officials, the International Civil Aviation Organization expressed the organization's "grave concern" over the potential for LightSquared's technology to disrupt or degrade GPS signals.

Deputy Defense Secretary Bill Lynn has raised concerns that LightSquared’s new system would interfere with military GPS signals.

The National Space-Based PNT Systems Engineering Forum (NPEF) has completed a study of interference to GPS users from the broadband network being developed by LightSquared. The study provides conclusive evidence, based on simulated and real-world testing, that LightSquared’s planned signals interrupt a broad range of GPS-based services — including farming systems, emergency vehicle dispatch, aircraft avionics and survey operations.

“Live sky” tests in New Mexico with actual LightSquared transmissions degraded GPS service on all devices tested. Analysis of the data collected indicates aircraft would lose GPS at up to 8.6 km from a LightSquared tower. The NPEF investigated various mitigation options, but found no universal approach to resolve the issue for all GPS users under LightSquared’s current FCC authorization.