SpaceX is aiming to launch a Starlink cellular service next year, with the goal of supplying satellite-based messaging and internet to smartphones. But the company still needs to convince the FCC that the technology won’t interfere with other satellite and ground-based services.

On Tuesday, the FCC sent a list of additional questions to SpaceX as the US regulator considers whether to approve or reject the company’s application to operate the Starlink cellular service over the 1910 to 1995MHz radio bands.

The company initially applied last year to begin using thousands of Starlink satellites to beam the radio signals to smartphones on the ground, including those from T-Mobile. Now, the FCC is requesting that SpaceX supply an “interference analysis."

“This analysis should take into account the worst case scenario of all satellites transmitting at the same time, including different power levels required for rain fade and cloud cover as well as clear sky conditions over a particular area of coverage,” the FCC wrote.

In addition, the same analysis should look at the “possibility of loss of service by other authorized satellite and terrestrial operators in that area,” the Commission added.

Another request asks SpaceX to provide “a map with projected beam coverage” for the US, showing the maximum and typical power levels of the satellite cellular service. The FCC also wants to know how the company can shut down the cellular Starlink system in the event interference arises over certain geographic areas.

“If SpaceX is required to cease operations due to harmful interference when the satellites are serving populated areas that already have full terrestrial coverage, how will this be accomplished with multiple satellites or multiple coverage areas simultaneously?” the FCC asks.

The letter arrives when other companies have expressed concerns to the FCC about the Starlink cellular system causing interference. US-based Omnispace, a satellite communications provider, even told the Commision that the interference is unavoidable for its own S-Band satellites, which operate using the 1980-2010MHz frequency.

“Because Omnispace’s satellites are in constant motion, as are SpaceX’s, the interference Omnispace will see will be constant and pervasive for any of our satellites operating at distances 5,400 km from any US territory where SpaceX is operating a single satellite in its proposed SCS system,” the company said back in August. Omnispace also created a map, showing an "exclusion zone" to depict the regions the alleged Starlink interference would occur.

SpaceX didn’t immediately respond to a request for comment. But in September, the company told the FCC that Omnispace was making false claims about the Starlink cellular service posing an interference risk. SpaceX also alleged that Omnispace was focused on serving foreign customers, rather than US users.

“SpaceX will not cause harmful interference to Omnispace’s speculative foreign system, and Omnispace’s shapeshifting analysis provides no basis for the Commission to delay the deployment of beneficial services to millions of American consumers,” the company said.