HGS-1
Encyclopedia
PAS-22, previously known as AsiaSat 3 and then HGS-1, was a geosynchronous communications satellite
which 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.
Edward Belbruno
and Rex Ridenoure heard about the problem and proposed a 3-5 month low energy transfer trajectory that would swing past the moon and leave the satellite in geostationary orbit around the earth. Hughes had no ability to track the satellite at such a distance, and opted instead for an Apollo-style free return trajectory
that required only a few days to complete. This maneuver removed only 40 degrees of orbital inclination and left the satellite in a geosynchronous orbit, whereas the Belbruno maneuver would have removed all 51 degrees of inclination and left it in geostationary orbit.
Although Hughes did not end up using the low-energy transfer trajectory, the insight to use a lunar swingby was key to the spacecraft rescue. Hughes had not considered this option until it was contacted by Ridenoure.
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 manoeuvres. 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 satellite's two 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. It was deactivated in July 2002, and moved to a graveyard orbit
.
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
which was salvaged from an unusable geosynchronous transfer orbit by means of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
's gravity.
AsiaSat 3 was launched by AsiaSat Ltd
AsiaSat
Asia Satellite Telecommunications Co. Ltd. is a commercial operator of communication spacecraft. AsiaSat is based in Hong Kong with two major shareholders, CITIC and General Electric.-Satellites:...
of Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
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.
Edward Belbruno
Edward Belbruno
Edward Belbruno is a mathematician whose interests are in celestial mechanics, dynamical systems, dynamical astronomy, and aerospace engineering....
and Rex Ridenoure heard about the problem and proposed a 3-5 month low energy transfer trajectory that would swing past the moon and leave the satellite in geostationary orbit around the earth. Hughes had no ability to track the satellite at such a distance, and opted instead for an Apollo-style free return trajectory
Free return trajectory
A free return trajectory is one of a very small sub-class of trajectories in which the trajectory of a satellite traveling away from a primary body is modified by the presence of a secondary body causing the satellite to return to the primary body...
that required only a few days to complete. This maneuver removed only 40 degrees of orbital inclination and left the satellite in a geosynchronous orbit, whereas the Belbruno maneuver would have removed all 51 degrees of inclination and left it in geostationary orbit.
Although Hughes did not end up using the low-energy transfer trajectory, the insight to use a lunar swingby was key to the spacecraft rescue. Hughes had not considered this option until it was contacted by Ridenoure.
Rescue of satellite
Using on-board propellant and lunar gravity, the orbit's apogee was gradually increased with several manoeuvres at perigeePerigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...
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
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
.
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 manoeuvres. 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 satellite's two 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
PanAmSat
The former PanAmSat Corporation founded in 1984 by Reynold Anselmo, was a satellite service provider headquartered in Greenwich, Connecticut. It operated a fleet of communications satellites used by the entertainment industry, news agencies, internet service providers, government agencies, and...
, renamed to PAS 22, and moved to 60° W. It was deactivated in July 2002, and moved to a graveyard orbit
Graveyard orbit
A graveyard orbit, also called a supersynchronous orbit, junk orbit or disposal orbit, is an orbit significantly above synchronous orbit, where spacecraft are intentionally placed at the end of their operational life...
.