Chandrayaan-2: The Geosynchronous Satellite Launch Vehicle–Mark III-M1 (GSLV Mark III-M1) used to launch Chandrayaan-2 effectively positioned the satellite at 170 km perigee (nearest distance from the earth) and 45.475 km apogee (farthest distance from the earth) in the Earth Parking Orbit (EPO). The earth parking orbit’s apogee is more than initially planned about 6,000 km.
Therefore, the number of earth-bound steps or maneuvers needed to take the satellite to the highest orbit of nearly 1,44,000 km apogee has been reduced from seven to six, says K. Indian Space Research Organization (ISRO) Chairman Sivan. The decreased amount of maneuvers will result in savings in fuel.
The perigee was boosted from 170 km to about 230 km in the first orbit-raising practice on July 24, while the apogee was lowered from 45,475 km to 45,162 km. Explaining why the orbit raising was performed primarily to raise the perigee rather than the apogee, Mr. Sivan told The Hindu: “At 169.7 km altitude at the perigee, the satellite is still in the earth’s atmosphere and thus subjected to heat stress while traveling at a very elevated speed. So we had to raise the perigee. “Tonight (July 25) the second maneuver to raise the orbit will be undertaken when the focus will be to increase the apogee to a large extent, while the perigee distance will only increase slightly.
The apogee is improved in measures after the satellite is positioned in the Earth Parking orbit to bring it to the final earth-bound orbit of approximately 1,44,000 km. In elliptical courses the satellite rolls around the planet and in order to raise the apogee, when it is closer to earth (perigee), the satellite is ignited. Currently, only five orbit-raising maneuvers are listed on the ISRO website and the perigee range listed is 241,5 km after the first workout in orbit-raising. “It’s going to be revised shortly,” he said