View source for GSAT-1

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{{Infobox spaceflight
| name                  = GSAT-1
| image                 = 
| image_caption         =

| mission_type          = Communications<br/>Technology
| operator              = [[Indian Space Research Organisation|ISRO]]
| COSPAR_ID             = 2001-015A
| SATCAT                = 26745
| mission_duration      = Failed to reach orbit

| spacecraft_bus        = [[I-2K]]
| manufacturer          = [[Indian Space Research Organisation|ISRO]]
| launch_mass           = {{convert|1540|kg}}
| power                 =

| launch_date           = {{start-date|18 April 2001, 10:13|timezone=yes}}&nbsp;UTC
| launch_rocket         = [[Geosynchronous Satellite Launch Vehicle|GSLV Mk.I]]
| launch_site           = [[Satish Dhawan Space Centre|Shiharikota]] [[Satish Dhawan Space Centre First Launch Pad|FLP]]
| launch_contractor     = [[Indian Space Research Organisation|ISRO]]

| orbit_epoch           = 25 April 2001<ref>{{cite web|url=http://planet4589.org/space/log/satcat.txt|title=Satellite Catalog|first=Jonathan|last=McDowell|work=Jonathan's Space Page|access-date=27 September 2013}}</ref>
| orbit_reference       = [[geocentric orbit|Geocentric]]
| orbit_regime          = [[Medium Earth orbit|Medium Earth]]<br/><small>[[Geostationary orbit|Geostationary]] planned</small>
| orbit_periapsis       = {{convert|33800|km|mi}}
| orbit_apoapsis        = {{convert|35725|km|mi}}
| orbit_inclination     = 0.9&nbsp;degrees
| orbit_period          = 1384.09&nbsp;minutes
| orbit_longitude       = 73°&nbsp;west (2000)<br/>99°&nbsp;west (2000–2006)<br/>76.85°&nbsp;west (2006–2009)
| orbit_slot            = 
| apsis                 = gee

| trans_band            = 3&nbsp;C-band<br/>2&nbsp;S-band
| trans_frequency       = 
| trans_bandwidth       = 
| trans_capacity        = 
| trans_coverage        = 
| trans_TWTA            = 
| trans_EIRP            = 
| trans_HPBW            = 
| programme             = [[GSAT]]
| next_mission          = [[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.<ref>{{Cite web |date=2025-01-17 |title=GSAT-30: Advancing India's Communication and Digital Connectivity. |url=https://environmentsandscience.blogspot.com/2025/01/gsat-30-advancing-indias-communication.html |access-date=2025-01-17 |website=Environmentsandscience |language=en}}</ref> 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.

==Overview==
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&nbsp;km, inclined at 19.2 degrees, having an [[apogee]] about 4,000&nbsp;km below the targeted orbit of 185 x 35.975&nbsp;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.

=== Launch attempt summary ===
{{LaunchAttempt
| date1           = 2001-03-28, 10:00 UTC 
| result1         = Scrubbed 
| reason1         = 
| decision_date1  = 2001-03-28
| notes1          = Abborted due to some engines related issues in the terminal count.
| date2           = 2001-04-18, 10:13 UTC
| result2         = Partial failure 
| weathergo2      = 
| notes2          = Payload placed into lower than planned orbit, and did not have sufficient fuel to reach a usable orbit.
}}

==See also==
{{Portal|Spaceflight}}
*[[List of Indian satellites]]

== References ==
<references />

{{GSAT Satellites}}
{{Indian spacecraft}}
{{Orbital launches in 2001}}

{{DEFAULTSORT:Gsat-1}}
[[Category:GSAT satellites]]
[[Category:Spacecraft launched in 2001]]
[[Category:Satellite launch failures]]
[[Category:2001 in India]]
[[Category:Spacecraft launched by GSLV rockets]]