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Irs
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The Indian Remote Sensing Satellite (IRS–1C) was successfully launched into polar orbit on December 28, 1995 by a Russian launch vehicle. Its payload was activated in the first week of January 1996. This satellite was followed by a similar one that was successfully launched into polar orbit on September 29, 1997 by a PSLV launch vehicle. Its payload was activated in mid-October 1997.
Orbit
The primary objective of IRS satellites is to provide systematic and repetitive acquisition of data of the Earth’s surface under nearly constant illumination conditions. IRS–1C operates in a circular, sun-synchronous, near polar orbit with an inclination of 98.69°, at an altitude of 817 km in the descending node. The satellite takes 101.35 minutes to complete one revolution around the earth and completes about 14 orbits per day. The entire earth is covered by 341 orbits during a 24 day cycle. Successive orbits are shifted westward by 2820 km at the equator. IRS-1C and 1D have slightly different orbits (see below) and for this reason do not have the same reference system.
The mean equatorial crossing time in the descending node is 10.30 a.m. ± 5 minutes. The orbit adjust system is used to attain the required orbit initially and it is maintained throughout the mission period. The ground trace pattern is controlled within ± 5 km of the reference ground trace pattern. |
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