INSAT-3B has been successfully collocated with INSAT-2E at 83 degree East Longitude. The collocation was completed on April 4, 2000. In the last three days, quick look checks of all the transponders on board the satellite have been completed from the INSAT Master Control Facility at Hassan in Karnataka. The collocation interference tests have also been completed. Detailed characterisation of the transponders is now being carried out. INSAT-3B is expected to be commissioned into service by the third week of April, 2000.

It may be recalled that INSAT-3B was launched on March 22, 2000 by an European Launch Vehicle, Ariane. Subsequently, orbit raising manoeuvres to take the satellite from Geostationary Transfer Orbit (GTO) to Geostationary Orbit (GO) were carried out using the Liquid Apogee Motor on board. The deployment of two solar arrays and two antennas was completed on March 27, 2000 when the satellite was at 67.8 degree East Longitude and was moving slowly towards its final parking slot of 83 degree east longitude.

Collocation of more than one satellite in a single orbital slot enables optimum use of available orbital slots and the limited frequency spectrum. To the users on ground, the collocated satellites appear as a single satellite with a large capacity. The interference between the collocated satellites is avoided by making the satellites transmit signals which are polarised orthogonal to that of the other collocated satellites, thus, providing the required isolation. It may be noted that INSAT satellites now occupy four slots in the geostationary orbit -- INSAT-2B and INSAT-2C are collocated at 93.5 degree east longitude, INSAT-1D and INSAT-2A are collocated at 74 degree east longitude and INSAT-2DT is located at 55 degree east longitude besides INSAT-2E and INSAT-3B at 83 degree east longitude.