Preparations are on for launching Insat-3B by Ariane rocket from Kourou in French Guiana this September, an ISRO official in Bangalore said.

Meanwhile, the Government last month cleared ISRO's proposal to sign a contract with europe's Arianespace to launch its Insat-3A at a cost of Rs 352.7 crore from Kourou. The launch of Insat-3a is scheduled for the middle of next year.

Insat-3b precedes Insat-3A to make up for the extended C-band transponder losses suffered by ISRO when Insat-2D had to be abandoned due to an electrical short-circuit that occurred just four months after its launch in 1997.

Insat-3A, Insat-3B and Insat-3C are planned to augment the Insat transponder capacity to cater to the increased demand of about 130 transponders by 2002.

The 2.5-tonne Insat-3Awill carry a very high resolution radiometer (VHRR) and charged coupled device (CCD) camera similar to Insat-2E that was launched in April this year.

It will have a satellite aided search and rescue (SAS&R) and a data relay transponder (DRT), besides communications transponders in C-band, extended C-band and Ku band.

A preliminary design review of Insat-3A has been completed and its configuration finalised.