Comsat technology may cut satellite costs. But cost of adapting existing ground systems called a `trade-off'

The cost of long-distance telephone calls and other services carried by satellites could go down as a result of changes in technology which extend the life of communications satellites. A leading satellite company has developed a way to possibly double the life of communications satellites, by drastically reducing the amount of fuel they use in maintaining proper orbit.

The cost of putting a new communications satellite into orbit is about $200 million, and the satellites can run out of fuel in less than 10 years. Communications Satellite Corporation (Comsat) officials say the technique could play a critical role in boosting the industry's cost competitiveness.

Fuel, not electronics, is the chief limiting factor in a satellite's life expectancy, according to Comsat General Corporation's president, William Mayo. ``The most critical factor remains fuel consumption,'' Mr. Mayo says. ``One thing we can't do is refuel [satellites].''

Lacking that capability, satellite owners are forced to wait for their costly investments to run out of fuel. Industry officials say the average communications satellite is launched with about 300 pounds of fuel and uses 30 to 40 pounds of it each year trying to stay in geosynchronous orbit, that is, positioned over the same spot on Earth's surface.

But these satellites have a natural tendency to drift, particularly north and south, as much as 50 miles. Mayo says more than 90 percent of a satellite's fuel -- which is hydrozene, a compound of hydrogen and nitrogen -- is used to correct that drift.

The technique, which Comsat is seeking to patent, uses software and computer commands to adjust the angle of the satellite, so that regardless of its drift, its beam stays in constant contact with ground antennas programmed to move along with it.

``It's going to work,'' says Dominick Santarpia, program manager for communications technology at the National Aeronautics and Space Administration. ``But it will mean additional cost in adapting ground terminals.''

Some ground antennas already have the ability to follow satellite movements.

Comsat's Mayo says those that don't can be adapted for about $15,000 each. He adds that this might make it too costly for cable television providers and owners of backyard satellite dishes. But it could help some distribution networks with a high volume of data and voice transmissions.

Chief among these is the International Telecommunications Satellite Organization (Intelsat), which is 25 percent owned by Comsat. Intelsat operates 15 communications satellites for 112 member nations.

``The net effect [of the technique],'' says Intelsat spokesman Christopher Clough, ``is the possibility of passing along discounts to our users because our satellites would be working longer.''

More than half of Intelsat's 859 earth-bound antennas already have the capability to track satellite movement.

But for other major satellite owners, ``it's a cost trade-off,'' says Judy Sauter, manager of flight dynamics for MCI Communications. ``It's a trade-off between [the life of] your satellite and [the cost of adapting] your ground network,' ' she says.

Ron Lepkowski of the Federal Communications Commission says that ``it makes a lot of sense for some systems, and not much for others.''

There is some debate over just how new the tilt technique is. NASA and some industry officials say they've been able to tilt satellites for more than a decade. They cite the high cost of retrofitting earth antennas as an economic stumbling block.

But new competing technologies, such as fiber optics cable, are making inroads into the services that satellites traditionally provide. Mayo says that prolonging satellite life will make them ``more cost competitive with fiber optics cables.''

Another competitive factor is the severe shortage of spacecraft available to launch new satellites following the Challenger space shuttle disaster.

Hughes Aircraft Company has built more than half of the communications satellies now in orbit. Vice-president Steven Dorfman says his company is always trying new ways to extend the life of its satellites. ``Anything that helps [in extending a satellite's life] is good for us and we like it,'' says Mr. Dorfman.

Comsat officials say the technique should save significant amounts of fuel, changing slightly the satellite's orbital plan and requiring just 3 pounds a year, instead of the 37 pounds now used. This means that future satellites can be designed for longer life spans or accommodate more sophisticated electronics. There are upwards of 50 domestic satellites nearing the end of their lives 22,000 miles above Earth, and Comsat hopes many will be able to take advantage of the technique to keep them working well beyond their designed lifetime.