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Space

Crippled satellite repeats lunar orbits

animation
Computer animation of the satellite in Earth orbit  

In this story:

June 6, 1998
Web posted at: 8:12 p.m. EDT (0012 GMT)

(CNN) -- The HGS-1 satellite is making its second lunar pass, after becoming the first commercial satellite to orbit the moon.

The satellite, which was placed in the wrong orbit by a malfunctioning rocket, passed behind the moon the first time on May 13 and used lunar gravity to propel it back towards Earth. An engine burn on June 1 sent it back on a five-day return trip.


A L S O :

Live video of real-time position animation

Lunar Salvage Mission Orbital Trajectories

HGS-1, designed for high-powered satellite TV transmissions, was declared a total loss in December, because it did not have enough power to boost itself into the proper orbit 23,000 miles (36,800 km) from Earth.

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So the engineers at Hughes, which owns the satellite, decided to try something that hasn't been done since the Apollo moon landing program. During the last several weeks, they have fired the satellite's on-board rocket motor several times to nudge it out of its highly angled orbit of 217 miles by 22,300 miles (350 km by 36,000 km).

On May 7, they sent it on a six-day trip to the moon where it followed a three-dimensional, figure-8 path, using lunar gravity to hurl it back toward Earth.

The maneuver used most of the 3,700 pounds (1,665 kg) of propellant aboard the satellite. But if it is successful, HGS-1 will assume a circular orbit over Earth's equator by the end of May. Engineers plan to begin braking maneuvers Saturday.

satellite
Click for a larger picture  

A benefit to future missions?

"There were some naysayers, myself included," said Mark Skidmore, project manager for the mission. "But it's evolved into one of those things that kind of went from 'Gee, I don't know. I don't think so' to 'Yeah, we can do this.'"

This is the first time a commercial satellite has traveled to the moon. It's also be the first time commercial operators have tried anything this extreme to bring a satellite back into the proper orbit.

Assisting HGS with the mission are the U.S. and Air Force Space Commands, NASA's Goddard Space Flight Center and EMBRATEL, a Brazilian company.

"While NASA has used gravity assists to send spacecraft off on interplanetary missions, no one has ever tried it to bring a communications satellite back into Earth orbit," said Ronald V. Swanson, HGS president, in a company news release.

Swanson noted that a similar "free return trajectory" was employed nearly 30 years ago during the early Apollo missions.

Another company spokesman said if the technique works, it raises the possibility of reduced costs for future space missions.

"While we haven't yet begun exploring what a standard lunar injection to geosychronous (orbit) really means, it's true we may be able to reduce the cost of some missions or even boost more payload in orbit for the same cost," said Mark Schwene, a vice president for Hughes Global Services. "Either of these could significantly benefit future satellite programs."

satellite

'A powerful, capable satellite'

Hughes said the satellite is fully functional and capable of covering more than a quarter of the Earth at any time. It had been kept in a stowed and dormant state until the engineers decided what to do with it.

It was built to provide television distribution and telecommunications services throughout Asia, India, the Middle East, Australasia and the Commonwealth of Independent States, made up of 11 former Soviet republics.

Hughes has funded the salvage mission itself and, if successful, wants to put the satellite to work. The company does most of its business with governments and military customers, and says it will share the profits with the insurance underwriters.

"It's a very powerful, capable satellite," Swanson said, "and the potential applications are great if we can get it into a usable orbit. Keep in mind, however, that nothing like this has ever been done and it is still an experiment."

Correspondent John Holliman contributed to this report.

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