GSat-12, the nation's latest communications satellite, was put in orbit on Friday, adding a small number to the space agency's total transponder capacity.

Quick-fix solution

The 1,400-kg spacecraft is ISRO's quick-fix solution to fill a part of its never-before capacity gap - almost 33 per cent - in a small way. It will mainly support societal applications.

Conceived and assembled quickly after the loss of a large communications satellite, the GSat-5P, in December 2010, it is 30 per cent smaller than regular Insats that weigh over 2,000 kg.

GSat-12 will have about half their life, or some 5-8 years, because of the fuel that will be spent in moving it to greater distances.

It was also flown on a smaller PSLV vehicle instead of on the GSLV.

(The PSLV was used for a similar `equatorial launch' two other times but not as a contingency: It launched the Kalpana-1 weather satellite in 2002; and then for the Chandrayaan-1 of 2008.)

Transponders

The satellite was likely to start functioning in a month. Its 12 transponders in the extended C band would be used for search and rescue communications during disaster management, tele-medicine or video-conferenced-health consultations from remote villages; and tele-education besides supporting the numerous digitised VRCs (village resource centres), the ISRO Chairman, Dr K. Radhakrishnan, said after the launch from the Sriharikota spaceport in coastal Andhra Pradesh.

Currently, the domestic fleet of eight communications satellites provides 175 transponders; another 86 have been hired on foreign satellites, to support television and DTH operators, broadband and telephone services.

Recently, Dr Radhakrishnan said ISRO planned to nearly double capacity to 500 transponders during the 11th Plan period (2007-12). But successive launch mishaps had set it back.

A hunt is on to hire a suitable foreign satellite for a short time.

Take-off

ISRO said the 20-minute, pre-dusk flight around 5 p.m. was near-perfect, taking the satellite into a ‘sub-geostationary' orbit.

The spacecraft initially goes round the Earth in an elliptical path that is 276 km X 21,000 km.

Soon, scientists from the Master Control Facility at Hassan in Karnataka will start rounding the ellipse into a 36,000 km, 24-hour orbit; the operations done by firing the satellite's engines from the ground are called ‘orbit-raising' manoeuvres.

GSat-12 needs five such firings before it reaches its intended slot and starts working - in about a month, according to Dr Radhakrishnan. In 2010, arguably ISRO's annus horribilis, two GSLV rockets each carrying a precious communications satellite failed. ISRO lost nearly 40 transponders.

The experimental GSat-4 on April 15; GSat-5P with 24 transponders on December 25; and a dozen transponders or half of Insat-4B that went cripple in July.

Dr Radhakrishnan had told Business Line before the launch that even if there are several foreign satellites that can readily lease out their capacity, hiring them for a short term was no easy job.

Users' requirements needed to have the satellite in a particular location in orbit; in the right frequency. “You cannot expect the users to move their antennas ...”

Friday's PSLV-C17 – in a re-jigged version called XL - was the 19th indigenous flight and the 32nd to be launched from Sriharikota's Satish Dhawan Space Centre.

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