The Direct-to-Home television transponder space on Indian satellites has been completely booked even before their launch, a senior Indian Space Research Organisation official said on Sunday.

"All the 34 DTH transponders on INSAT satellites are fully booked," Antrix Corporation Executive Director K R Sridhara Murthi told PTI in Bangalore.

Antrix, the commercial arm of ISRO, markets the space agency's satellite building and launch capabilities, besides space images, to global customers.

State-run Doordarshan and private Zee group's Dish TV have booked slot for Ku band transponders, used for DTH service on INSAT-4 series of satellites.

ISRO plans to launch DTH capable INSAT-4A with 12 Ku transponders by June this year.

DTH comprises a table fan-sized satellite dish, a digital encoder and a smart card. The dish connects to the decoder, which is linked to the TV.

ISRO officials said besides the slots for Dish TV and DD's DTH service, Space TV, the Tata-Murdoch joint venture, has also sought transponders for DTH service on the INSAT satellites.

ISRO's next-generation satellites, INSAT-4B, will have 12 Ku band transponders. The space agency plans to build DTH-dedicated satellites INSAT-4C and INSAT-4G with 18 Ku band transponders each in the next few years to keep up with the demand from DTH players.

"There is a huge demand for DTH services and the players will evolve a unique business model through Cable TV operators to tap the Indian consumer," Murthi said.

Ahead of the launch of it's own satellites, ISRO tied up with Netherlands-based New Skies Satellites last June to lease its transponders for DD's DTH launch in India. DD's DTH will be the world's largest free-to-air DTH service.

The multi-year lease of the transponders on the NSS-6 satellite with six high-performance Ku band beams enabled DD to provide an initial bouquet of 30 free channels, 15 from DD and 15 from private channels as well as 20 radio channels.

"There are many players who are eyeing the Indian DTH market and they may unveil their plans soon," Murthi said.