Satellite rescue

Researchers have used a new technique to extend the service life of two communications satellites.

The two satellites would have been shut down prematurely and wasted remaining fuel if not for the new technique developed by researchers from Purdue University and Lockheed Martin, said Steven Collicott, a Purdue professor of aeronautics and astronautics.

Communications satellites, which are maintained in orbit about 22,500 miles above the Earth by the firing of small rocket thrusters, must be replaced shortly before they run out of fuel. Enough fuel must remain to get the satellites out of orbit to make room for their replacements.

While most new satellites have just one fuel tank, some older ones have four. So if one of the tanks empties before the others, the satellite loses control and has to be decommissioned, said Dr Boris Yendler, senior thermal system analyst at Lockheed Martin Mission Services in Sunnyvale, California.

The Purdue and Lockheed Martin engineers not only determined precisely how much fuel remained in each tank, but they also used a technique to "rebalance," or equalise, propellant levels in all of the tanks.