GSAT-1

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GSAT-1

Mission type	Communications Technology
Operator	ISRO
COSPAR ID	2001-015A
SATCAT no.	26745
Mission duration	Failed to reach orbit
Spacecraft properties
Bus	I-2K
Manufacturer	ISRO
Launch mass	1,540 kilograms (3,400 lb)
Start of mission
Launch date	18 April 2001, 10:13 (2001-04-18UTC10:13Z) UTC
Rocket	GSLV Mk.I
Launch site	Shiharikota FLP
Contractor	ISRO
Orbital parameters
Reference system	Geocentric
Regime	Medium Earth Geostationary planned
Longitude	73° west (2000) 99° west (2000–2006) 76.85° west (2006–2009)
Perigee altitude	33,800 kilometres (21,000 mi)
Apogee altitude	35,725 kilometres (22,198 mi)
Inclination	0.9 degrees
Period	1384.09 minutes
Epoch	25 April 2001[1]
Transponders
Band	3 C-band 2 S-band
GSAT GSAT-2 →

GSAT-1 was an experimental communications satellite launched aboard the maiden flight of the GSLV rocket. The spacecraft was equipped with instrumentation to test Pulse-code modulation (PCM) transmitting on S-band frequencies and transponders operating in the C-band.^{[citation needed]} The spacecraft was unable to complete its mission after a launch failure left it in a lower than planned orbit and propulsion issues prevented the satellite from correcting this via its own maneuvering system.

GSAT-1 failed to achieve its target orbit, which prevented it from fulfilling its primary communications mission. The 1.54-tonne satellite was orbiting with a period of 23 hours two minutes, instead of the planned 24-hour geosynchronous orbit, only permitting a limited series of experiments to be conducted, including digital audio broadcasting and compressed digital TV signal transmission.

The GSLV (Geosynchronous Satellite Launch Vehicle) suffered a performance shortfall during its first flight resulting in the injection of the experimental satellite into a geosynchronous transfer orbit (GTO) of 181 x 32.051 km, inclined at 19.2 degrees, having an apogee about 4,000 km below the targeted orbit of 185 x 35.975 km. The satellite used its onboard propulsion system to raise both its apogee and its perigee to geostationary orbit as well as to decrease the orbital inclination to zero, however its propellant was depleted prior to successfully raising its orbit. The satellite used two different propellant tanks, built in Germany and India, which resulted in an unequal flow of fuel, causing the spacecraft to tilt. (The two different fuel tanks were used because they were readily available). Recovery required the use of more propellant than planned which resulted in the satellite having no propellant left to complete its final circularization maneuver. The satellite was possibly used for a few communications experiments but the original purpose of demonstrating digital TV and audio broadcasts, as well as Internet services could not be fulfilled.

The Russian 12KRB cryogenic upper stage was planned to perform for 710 seconds, but its burn apparently lasted only 698 seconds. Another suspect for the shortfall is the launch vehicle navigation system which was derived from the PSLV which has flown only to low earth orbits.

• List of Indian satellites