This story was corrected on 2 April 2009.
1 April 2009—Scientists and engineers will gather in Europe this week to brainstorm about better ways of dealing with the increasingly dangerous amount of space debris orbiting our planet. But when you're the largest commercial satellite operation in the world, you don’t have time to wait for a better way.
In February, Bethesda, Md.–based Intelsat General Corp. got an urgent call. The U.S. Department of Defense needed more bandwidth for remote-controlled unmanned aerial vehicles operating over Iraq and Afghanistan, and needed it immediately. That meant that Intelsat would have to fly one of its geosynchronous satellites halfway around the world without running into the kind of orbital flotsam that recently had astronauts on the International Space Station taking shelter in the escape ship.
On 2 March, engineers at Intelsat’s satellite operations center, in Washington, D.C., started moving a satellite named Galaxy 26 from its spot 33 600 kilometers above South America to a new slot the same distance above the Indian Ocean.
Galaxy 26 had been serving as a relay for commercial video and data traffic. According to Tobias Nassif, Intelsat’s vice president of satellite operations and engineering, the satellite was ready for the move within a week of the military’s formal request. That was the time required to transfer the commercial data to another one of Intelsat’s 52 satellites, coordinate the move with other satellite operators to avoid a collision, and prevent Galaxy 26’s RF emissions from interfering with other satellites’ transmissions.
Shifting the satellite’s position was a little more involved than throwing it in the back of a moving van and hauling it to its destination, says Nassif. The engineers in Washington sent a command telling the satellite to fire its thrusters in two pulses, once during each half of its orbit. The double pulse was to ensure that the satellite’s path remained circular rather than going elliptical as it moved 550 km below geosynchronous orbit. Galaxy 26 drifted for 15 days along its much shorter temporary path.
Meanwhile, says Nassif, the satellites still circling the equator at the higher orbit passed it at a relative speed of 7 degrees per day, or roughly 215 km/h. Over the course of the fortnight, Galaxy 26 ”traveled” about 77 000 km from its old position to its new home along the geosynchronous belt. As the satellite neared its new perch, its controllers performed the thrusting maneuver in reverse, causing it to coast into its new 39-square-kilometer window above the Indian Ocean.
But with 350 active satellites out of a total of 1200 objects in geosynchronous orbit, didn’t Intelsat’s satellite wranglers fear a collision like the one that occurred in February when the Cosmos 2251 and Iridium 33 satellites were rudely introduced to each other at nearly 28 000 km/h?
”There is certainly a risk involved in any such maneuver,” Nassif admits. But he points out that the likelihood of a crash in geosynchronous orbit is much lower than in low Earth orbit, where there are thousands more stray objects. Among these are active satellites that don’t follow a nice orderly path and don’t all move in a single direction. In geosynchronous orbit, even the dead satellites march in lockstep, tracing lazy figure eights in the sky. But that means they still can cross the path of active satellites twice a day.