New Satellites to keep watch over space-based systems.

• Author: Magnuson, Stew
• Position: Space Technology

COLORADO SPRINGS, Colo. -- Two new satellites may be launched later this year that will help the U.S. defense community better understand what is happening to the multi-million dollar spacecraft it depends on for communications, remote sensing, eavesdropping and navigation.

The largest of the two satellites, the space-based space surveillance system, will travel in low-earth orbit and peer up at satellites in the geo-synchronous belt, which is about 24,000 miles above the earth. It is also where most communications satellites loiter in fixed positions.

Fred Doyle, vice president at Ball Aerospace's national defense business unit, said the SBSS spacecraft will allow the Air Force to keep track of its own assets as well as keep an eye on those of other nations. Ball partnered with Boeing to build the satellite.

The Air Force currently uses ground-based radar to track objects in space. This Cold War era system was initially used to search for incoming missiles from the Soviet Union. Most of the stations are configured to search the northern hemisphere. Even if there were more ground stations, that would leave large swaths of the oceans where there would still be blind spots, he said.

The Air Force uses the radar to create a catalog of items orbiting the Earth. "The intent is to use this asset to make that catalog more accurate and more current," he said.

The SBSS will use a gimbaled telescope rather than radar to keep an eye on objects.

It can confirm the location of satellites that are sent to certain orbital slots. Once placed in an allotted slot. such spacecraft remain in fixed positions. But plans often go awry.

The Air Force may use the satellite to determine if one of its own, or a rival nation's platform, arrived where it was supposed to arrive. If not, the telescope can determine its true position.

The SBSS will travel in a polar orbit, and make passes around the Earth several times per day. Its telescope can remained fixed on a spacecraft of particular interest, or look at several as it passes by.

It can examine objects in low-earth orbit, where many spy platforms operate, but since such satellites do not stay in fixed orbits, the amount of time it could train the telescope on such a spacecraft is short, he said. It could also potentially keep track of large pieces of space junk, the collection of debris, spent rockets, defunct satellites that litter outer space.

SBSS currently is scheduled for a five-year mission. The Defense...