HGS-1

HGS-1, formerly known as AsiaSat 3, is a geosynchronous communications satellite. It is notable in that it was salvaged from an unusable geosynchronous transfer orbit by means of the Moon's gravity.

AsiaSat 3 was launched by AsiaSat Ltd of Hong Kong to provide communications and television services in Asia by a Proton booster on 24 December, 1997, destined for an orbit slot at 105.5° E. However, a failure of the Blok DM3 fourth stage left it stranded in a highly inclined (51 degrees) and elliptical orbit, although still fully functional. It was declared a total loss by its insurers. The satellite was transferred to Hughes Global Services, Inc., with an agreement to share any profits with the insurers.

Using on-board propellant and lunar gravity, the orbit's apogee was gradually increased with several manoeuvers at perigee until it flew by the Moon at a distance of 6,200 km from its surface in May 1998, becoming in a sense the first commercial lunar spacecraft. Another lunar fly-by was performed later that month at a distance of 34,300 km to further improve the orbital inclination.

These operations consumed most of the satellite's propellant, but still much less than it would take to remove the inclination without the Moon assist manoeuvers. With the remaining fuel, the satellite could be controlled as a geosynchronous satellite, with half the life of a normal satellite - a huge gain, considering that it had been declared a total loss. The satellite was then maneuvered to geosynchronous orbit at 150–154° W. After the satellite was in a stable orbit, the satellite was commanded to release its solar panels which had been stowed during takeoff and maneuvering. Of the two satellite's solar panels only one released, and it became apparent that a tether was not operating correctly on board, which scientists attributed to heating and cooling cycles during the satellites operating in ranges not designed to while traveling to orbit. In 1999, HGS-1 was acquired by PanAmSat, renamed to PAS 22, and moved to 60° W.

References

* [http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Asiasat Asiasat 3/HGS 1 Mission Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.skyrocket.de/space/doc_sdat/asiasat-3.htm Gunter Krebs' page]
* [http://www.xs4all.nl/~carlkop/asiasat.html Collection of related press releases]