PAS-22

AsiaSat 3 → HGS-1 → PAS-22

Operator	AsiaSat (1997–1998) Hughes (1998–1999) PanAmSat (1999–2002)
Major contractors	Hughes ILS (LSP)
Bus	HS-601HP
Mission type	Communications
Flyby of	The Moon:[1] #1: 13 May 1998, 19:00 UTC #2: 6 June 1998, 16:30 UTC
Launch date	24 December 1997 23:19 UTC[2]
Carrier rocket	Proton-M/DM3
Launch site	Baikonur Site 81/23
Mission duration	15 years (planned)[3] 4 years (achieved)
COSPAR ID	1997-086A
Mass	3,400 kilograms (7,500 lb)
Orbital elements
Regime	Highly elliptical (1997–1998) Geosynchronous (1998–2002) Graveyard (2002—)
Longitude	105.5° East (intended) 158° West (1998) 62° West (1999-2002)[4]
Transponders
Transponders	28 G/H band (IEEE C band) 16 J band (IEEE Ku band)

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. ^[5]

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. ^[6]

Rescue of satellite

Using on-board propellant and lunar gravity, the orbit's apogee was gradually increased with several manoeuvres at perigee until it flew by the Moon ^[6] 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.^[4]

References

1. ^ "AsiaSat 3". http://www.xs4all.nl/~carlkop/asiasat.html. Retrieved 15 May 2010. 
2. ^ McDowell, Jonathan. "Launch Log". Jonathan's Space Page. http://planet4589.org/space/log/launchlog.txt. Retrieved 15 May 2010. 
3. ^ Krebs, Gunter. "AsiaSat 3, 3S / HGS 1 / PAS 22". Gunter's Space Page. http://space.skyrocket.de/doc_sdat/asiasat-3.htm. Retrieved 15 May 2010. 
4. ^ ^{a b} "Asiasat 3". The Satellite Encyclopedia. http://www.tbs-satellite.com/tse/online/sat_asiasat_3.html. Retrieved 15 May 2010. 
5. ^ "Hughes Goes to Moon to Salvage Satellite: First Commercial Lunar Mission.". Hughes Press Release. 29 April 1998. http://sse.jpl.nasa.gov/news/display.cfm?News_ID=33835. 
6. ^ ^{a b} "New Book Reveals How Engineers Saved Hughes Satellite on Christmas Day 1997". Space Daily. 11 January 2006. http://www.spacedaily.com/news/Book_Reveals_How_Hughes_Saved_ComSat_In_1997.html. 

• Asiasat 3/HGS 1 Mission Profile by NASA's Solar System Exploration
• Gunter Krebs' page
• Collection of related press releases