Globalstar LLC said it filed March 2 an application with the Federal Communications Commission for authority to offer ancillary terrestrial service (ATC) in the United States in conjunction with its mobile satellite services. ATC allows satellite operators to use their authorized satellite radio frequencies to integrate into their satellite service offerings a terrestrial wireless service that is similar to, but more limited than, cellular or PCS. The company said it plans to use its authority to enhance its coverage in urban areas, where buildings and other infrastructure can physically block satellite signals.