GSAT - 7: Indian Navy's dedicated Communications Satellite

GSAT - 7, Credits to respective owners

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GSAT is a series of Geosynchronous Satellites developed by ISRO to primarily boost and aid the INSAT series of a communications satellite. GSAT – 7 or Insat – 4F is one such GSAT communications satellite developed by ISRO for the exclusive use by the Indian Navy. When it was launched, the satellite became the first dedicated military satellite of India.

Since Indian was a major military power in the Indian Ocean, it has been a concern among defence analysts that the Indian Navy was still using the services of foreign commercial satellite-like Inmarsat for communications between ships.

This was raised as a serious security lapse since such data transmission are prone to leak and could jeopardize national security. Finally, on 30 August 2013, GSAT – 7 was launched into space atop an Ariane – 5ECA rocket from Kourou, French Guiana. After about 34 minutes into the flight, the satellite was injected into a Geosynchronous Transfer Orbit (GTO) of 249km perigee. 

Five days later, three orbit raising manoeuvres were performed from ISRO's Master Control Facility at Hassan in Karnataka. The transponders were successfully switched-on on September 18^th. 2013.

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OBJECTIVE & PAYLOAD

The satellite is called ‘Rukmini’ in local circles but still holds the official name of GSAT – 7. The satellite provides communication to Indian Navy assets in multiple bands. It will provide communication in UHF, C-band and Ku band.

The satellite is based on ISRO’s I-2K satellite bus which is a modular satellite design for satellites in the 2000kg category. The communication equipment onboard has a power demand of 2000W of power, which is provided by two solar panels producing a total of 2500W peak output.

For attitude control, the satellite is equipped with a Liquid Apogee Motor (LAM) providing a thrust of 440N. The motor uses oxides of Nitrogen as oxidizer and Unsymmetrical Dimethylhydrazine(UDMH) as fuel. The motor under a mixture ratio of (O/F) of 1.65 and a nozzle ratio of 160. The engine’s injector is a co-axial swirl element made of titanium while the thrust chamber is constructed of Columbium alloy that is radiative cooled. The engine is certified for long firings of up to 3,000 seconds.

GSAT – 7 in a glimpse

• Launch Mass: 2650kg

• Launch Vehicle: Ariane – 5ECA

• Orbit altitude: 35,806km (Apogee) / 35,779km (Perigee)

• Inclination: 0.06 degrees

• Design life: 9 years

• Type/Application: Military Communication

• Manufacturer: ISRO

• User: Indian Navy