"The transponders are more than fully booked...We didn't have INSAT-4C (which was lost). So there is a shortage of 12 transponders. Before the launch itself, most of the capacity has been allotted to various users," ISRO chairman G Madhavan Nair told PTI.
Identical to INSAT-4A, the telecommunications satellite INSAT-4B carries 12-Ku and 12-C band transponders. The 3025-kg spacecraft is slated to be launched by an Ariane 5 rocket from the spaceport of Kourou in French Guiana early on Saturday.
ISRO officials said each transponder is sold for close to a $1 million every year. The satellite has a lifespan of 12 years.
The development cost of INSAT-4B, primarily intended for DTH applications, is Rs 210 crore (Rs 2.10 billion), while the launch cost charged by European space consortium Arianespace is Rs 225-230 crore (Rs 2.25-2.3 billion). Its insurance cost is Rs 60 crore (Rs 600 million).
Nair said ISRO is planning to launch INSAT-4CR, a replacement of INSAT-4C, from Sriharikota in the middle of this year. "With that, we will be able to just meet our immediate requirements (for DTH transponders)".
INSAT-4B is the second-last satellite that will be launched from foreign soil. One more satellite that would be launched from overseas - INSAT-4G - is two years away.
"We will have one more satellite launch from outside. The demand is going high. We will build one more heavy satellite. Besides that, we will not go outside," Nair, secretary in Department of Space and Chairman of Space Commission, said.
India already has the capability to launch two-tonne class satellites. Space scientists are developing GSLV-Mk III, which is expected to be operational in 2010 giving the country the capability to launch satellites up to four tonnes.
Nair, meanwhile, has suggested the new DTH transponder users adopt new techniques that would cut down their bandwidth requirement by up to two-third.
"There is a lot of demand for DTH programmes. I have been advising them that they should try and integrate their requirements and may go in for modern techniques so that the number of transponders can be effectively utilised," he said.
"It (demand for DTH transponders) is going like wildfire. Today we are talking to users. In fact, some of the (old) users have adopted techniques by which bandwidth requirement is compressed quite a bit....even a third of the capacity needed," Nair said.
While this technology now available in Europe would lead to 'considerable amount of compression' in bandwidth requirement, the demand for capacity for high-definition TVs is expected to go up."So there again, bandwidth requirement will go up. So it's a never-ending game. The number of slots available for us is limited and the number of satellites you can put there are limited. So with that capacity, we have to serve the whole country. I hope some stability will come as time goes," he added.