GSAT-15, the mainly communications satellite being put in space next week, will replace two older spacecraft that will likely expire in the coming months.

Its 24 transponders are solely in the Ku band and will cater to DTH (direct-to-home) television first, besides supporting the thousands of VSAT operators who provide broadband services; and DSNG (digital satellite news gathering) for TV news channels.

GSAT-15 will not add new transponder capacity to the country; it will ‘ensure sustainability of service’for the capacity-hungry DTH sector, according to A.S. Kiran Kumar, Chairman of Indian Space Research Organisation and Secretary, Department of Space. It will also carry the third GAGAN satellite navigation transponder as a back-up for airlines and other users of augmented GPS-based systems.

Leased transponders

Indian DTH broadcasters have been forced to lease 59 transponders on foreign satellites over the region; less than half of that capacity (26) is allotted for DTH on Indian communication satellites, mainly to Doordarshan and Tata Sky.

The immediate focus is on bridging the Ku-band shortage, Mr. Kiran Kumar told The Hindu .

“There is a constraint on spectrum. We want to reduce dependence on external transponders in about two years. We are in the process of finalising a solution for it. But I cannot spell out details.”

The heavyweight 4,000-kg-class GSAT-11 due in a couple of years, would add a significant number of transponders for national users, he said.

GSAT-15, weighing 3,164 kg, will be launched in the wee hours of November 11 (IST) from Kourou in French Guiana (in South America) on the European Arianespace’s Ariane-5 launcher.

The satellite cost and the launch fee are around Rs. 860 crore.

GSAT-15 will be flown along with Saudi Arabia’s Arabsat-6B/Badr-7.

To be stationed over the country at a slot at 93.5 degrees East longitude, the upcoming satellite must quickly replace INSAT-3A and INSAT-4B that are completing their tenure-- one in November and another later next year, Mr. Kiran Kumar said.

INSAT-3A, launched in April 2003, has completed its 12-year life. INSAT-4B, flown in March 2007, got reduced to half its functions in 2010 after one of its two power-generating solar panels developed a snag.

The two Indian rockets -- PSLV and GSLV -- cannot pitch the weight of GSAT-15 to its slot 36,000 km high. Mr. Kiran Kumar said ISRO had signed up Arianespace to launch GSAT-17, GSAT-18 and the heavier GSAT-11.

Its transponders will cater to DTH television, besides supporting VSAT operators who provide broadband services