INSAT-3A, next in ISRO's range of communication satellites, is ready for launch and will soon be put into orbit by an Ariane space launcher from French Guyana in another fortnight.

According to sources in the Indian Space Research Organisation the launch was delayed by a few weeks due to some technical problem with Ariane-5, the rocket scheduled to lift the satellite into space.

The date of launch has still not been finalised, but is expected to be around April 8 or 9.

Since its inception, ISRO has been launching INSAT series satellites using the Ariane space launch vehicles. ISRO's own launch vehicle the GSLV [Geo-stationary Satellite Launch Vehicle] does not have the capacity to launch such heavy satellites.

Of the five satellite series [INSAT-3A through INSAT-3E] planned, INSAT-3B and INSAT-3C have already been launched under the INSAT-3 series.

INSAT-3A has communication transponders in C-band, extended C-band and Ku-band, as well as meteorological instruments comprising a very high resolution radiometer, charge coupled device camera, data relay transponder and search and rescue payloads.

ISRO sources say it is designed mainly to support and augment ISRO's existing facilities and does not posses any unique or new functions to perform.

INSAT-3B was launched by Ariane-5 launch vehicle in March 2000. It is co-located with INSAT-2E at 83 degrees east longitude.

INSAT-3C was launched by an Ariane-4 launch vehicle on January 24, 2002. It is positioned at 74 degrees east longitude.

INSAT-2D was a failed attempt on October 4, 1997. ISRO then procured a satellite from the ARABSAT organisation that was already in use to provide whatever additional facility was to have come from INSAT-2D.

This satellite, which was actually called ARABSAT-1C, was re-named INSAT-2DT. It is located at 55 degree east. It has 25 C-band transponders and one S-band BSS transponder, used mainly by Doordarshan and BSNL.

INSAT-3A will replace this satellite and ISRO can return the leased facility to the ARABSAT organisation, which is a regional inter-governmental satellite consortium of Arab States.

INSAT-3E is also scheduled for launch in 2003. ISRO also just launched its meteorology satellite Kalpana, named after the Indian-born astronaut who died in the recent Columbia space crash.

Development of a more powerful vehicle, the GSLV Mark III, has been taken up and is targeted at being capable of carrying double the payload capacity of the present version.

The INSATs are geo-stationary satellites placed in an orbit, about 36,000 km over the equator and at that altitude the satellite has an orbital period of 24 hours and hence appears to be stationary with respect to any point on the earth.

They, therefore, can be used as a stationary platform for telecommunication, television broadcasting and meteorological services.

The Geo-stationary Satellite Services in India were commissioned in 1983 with the launch of INSAT-1B.

In the present day INSAT is one of the largest domestic communication satellite systems in the Asia Pacific Region with five satellites [INSAT-2DT, INSAT-2E, INSAT-3B, INSAT-3C and KALPANA-1] in operation.

INSAT system is a joint venture of the Department of Space, Department of Telecommunications, India Meteorological Department, All India Radio and Doordarshan.

The overall coordination and management of the INSAT system rests with Secretary-level INSAT Coordination Committee.