WASHINGTON — Intelsat’s five-year-old Galaxy 15 satellite stopped responding to commands early April 5, prompting the company to begin moving an on-orbit spare to the balky satellite’s 133 degrees west longitude orbital slot to avoid an interruption in service, Intelsat of Washington and Luxembourg announced April 8.

Intelsat spokeswoman Dianne VanBeber said Galaxy 15’s transponders remain fully functional and that there have been no service outages. But controllers have not been able to re-establish contact with the craft, a Star platform built by Orbital Sciences Corp. of Dulles, Va.

Intelsat has already begun moving the Galaxy 12 satellite, also built by Orbital and launched in 2003, from its holding location at 123 degrees west to Galaxy 15’s position, VanBeber said. It is expected to arrive April 14, at which time Intelsat will begin transferring Galaxy 15’s commercial users to the older but similar satellite, she said.

“We have plenty of time based on how [Galaxy 15] is operating,” she said.

Galaxy 15 carries 24 C-band transponders serving media customers in North America and an L-band payload used by the U.S. Federal Aviation Administration. Galaxy 12 carries a virtually identical C-band package but does not carry any additional payloads, VanBeber said.

Intelsat has six Orbital-built Star platforms on orbit and another three under construction. The company has not previously experienced any problems like the one afflicting Galaxy 15, VanBeber said.

“We’re working with Orbital to do a complete and thorough investigation and are mindful of the fact that we have other satellites in production with them right now,” VanBeber said.

VanBeber said it is too early to tell whether engineers will be able regain control of Galaxy 15 and put it back into service. Galaxy 15, designed to operate through 2022, was not insured in keeping with Intelsat’s policy of covering its spacecraft through launch plus one year on orbit.

Warren Ferster is the Editor-in-Chief of SpaceNews and is responsible for all the news and editorial coverage in the weekly newspaper, the spacenews.com Web site and variety of specialty publications such as show dailies. He manages a staff of seven reporters...