Transponder: GSAT-12 will only minimally offset shortfall

Communication satellite GSAT-12 of the Indian Space Research Organisation (ISRO), which will be launched on July 15 by the Polar Satellite Launch Vehicle (PSLV-C17) from Sriharikota, will only minimally offset the huge shortfall of transponder capacity that the organisation is facing today, particularly in C and Ku frequency bands.

GSAT-12 carries 12 Extended C-band (xt-C) transponders (of 36 MHz bandwidth each) and much of this will go towards ISRO's own national communication projects and partly towards meeting the requirement of VSAT operators and closed user group (CUG) networks. Of course, the demand for xt-C band from VSAT operators has declined substantially over the years because of their migration to the preferred high-frequency and Ku band.

While GSAT-12 has been billed as a replacement satellite for INSAT-3B, which was launched in 2000 and decommissioned last year, it does not carry the 5 Ku transponders that the INSAT-3B had. The Ku transponders are in demand not just for telecom services but for the DTH (direct-to-home) television operations as well.

The total transponder capacity in space after the launch of GSAT-12, including the 24 Ku-band transponders on GSAT-8 that was launched aboard Ariane on May 21, will be 175. GSAT-8 is yet to be declared operational but that is expected to happen soon as all the requisite in-orbit tests are over, according T. K. Alex, director of ISRO Satellite Centre (ISAC) in Bangalore.

According to ISRO, the break-up of the availability of the 175 transponders on the various operational INSAT satellites is as follows:

INSAT-2E (Launch: April 3, 1999) 19; INSAT-3C (Launch: January 24, 2002) 33; INSAT-3A (Launch: April 10, 2003) 24; INSAT-3E (Launch: September 28, 2003) 25; INSAT-4A (Launch: December 22, 2005) 24; INSAT-4B (Launch: March 12, 2007) 14; INSAT-4CR (Launch: Sept. 2, 2007) 12; GSAT-8 (Launch: May 21, 2011) 24 — Total: 175

INSAT-4B suffered a serious power anomaly in one of its solar panels and it resulted in nearly half of its original transponder capacity (12 Ku-band and 12 C-band) becoming unavailable after July 7, 2010.

This affected many DTH operators. The non-availability of 11 of INSAT-3E's total 36 (24 C-band and 12 xt-C band) transponders is due to their subsequent failure on-board, according to ISRO's information officer Satish.

It may also be recalled that 11 of the 19 C-band transponders aboard INSAT-2E was leased to the INTELSAT consortium for 10 years soon after the satellite's launch in 1999.

These, in turn, were chiefly procured by Indian operators from INTELSAT. This lease has now been extended up to the end of INSAT-2E's life, which is likely to be 2011-end. Though, technically speaking, only 8 transponders of INSAT-2E are under the ISRO's control, since all are being used by Indian operators, these 11 were included in the above table, Mr. Satish said.

Taken on lease

Besides the above, the ISRO has taken on lease 86 transponders (mostly in the Ku-band) from different foreign satellites. Despite that there will remain an unmet demand of 170 transponders on the ISRO's waitlist. According to ISRO Chairman K. Radhakrishnan, the organisation was negotiating with various satellite operators to lease transponders from their satellites.

The next telecom satellite of the ISRO that is scheduled to be launched is GSAT-10. It will carry 30 transponders in all – 12 in the C-band, 12 in the Ku-band and 6 in the xt-C band.

However, like GSAT-8, its launch will be aboard Ariane and is scheduled for April 2012.

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