The LightSquared booth at Satellite 2011 Convention at the Washington Convention Center in D.C. in March (Jeffrey MacMillan/FOR THE WASHINGTON POST)

In a letter from FCC engineering and technology chief Julius Knapp, the agency asked both parties to spell out exactly what devices see interference and how those devices will interact with LightSquared’s newly scaled-down deployment plan.

Knapp asked the GPS industry to provide some more specifics about the number and lifespan of devices that it believes interfere with the spectrum licensed to LightSquared for the deployment of its satellite broadband network.

The agency also requested that LightSquared provide more information about how many base stations it plans to deploy under its scaled-back plan. Originally, LightSquared had said it would deploy 40,000 base stations, but it has not provided an updated figure since it submitted a revised plan to roll out its network in a more limited band of spectrum.

The controversy over LightSquared has attracted more scrutiny of the FCC, which has supported LightSquared’s mobile broadband ambitions. LightSquared has recently asked GPS technology providers to use filtering technology to avoid interference.

At its monthly meeting Tuesday, agency officials said that the network would not be allowed to deploy if it interfered with GPS services, Reuters reported.