IRS-1D

Launch

The 1250 kg IRS-1D is an Indian remote sensing Sun-synchronous orbiter that was launched by the PSLV-C1 (Polar Satellite Launch Vehicle) launch vehicle from Sriharikota (in southeast India) at 04:47 UTC. The 44.4 metres, four-stage, 494-ton PSLV-1C is now an operational vehicle, after earlier test launches, it is the fourth launch vehicle PSLV. Orbit maneuvers may be planned to raise the perigee.

Due to a slight under performance of PSLV fourth stage, IRS-1D was injected with a velocity that was 130 m/sec less than the required 7446 m/sec. This minor shortfall in the injection velocity resulted in IRS-1D being injected into a polar orbit with an apogee of 822 km and a perigee of 301 km instead of the intended 817 km circular orbit. But, ISRO scientists, monitoring and controlling the satellite from ISRO Telemetry, Tracking and Command Network (ISTRAC) executed meticulously planned orbit manoeuvres to successfully put IRS-1D into a functional Sun-synchronous orbit of 740 km perigee and 817 km apogee.