Chandrayaan-1 successfully enters lunar orbit
08 Nov 2008
ISRO is confirming the successful insertion of India's lunar orbiter Chandrayaan-1 into the Lunar Orbit of Injection. India's first unmanned moon mission Chandrayaan-I was Saturday put into lunar orbit at around 5.15 p.m., scientists of the Indian Space Research Organisation (ISRO) said here.
The spacecraft was successfully put into an elliptical orbit after complex manoeuvres.
"The liquid apogee motor on board the spacecraft was fired for about 805 seconds to put Chandrayaan-1 into an elliptical orbit with 7,500 km apolune (farthest from moon) and 500 km perilune (nearest to moon)," ISRO director S. Satish said.
The manoeuvre now unshackles the Chandrayaan from the earth's gravitational pull forever and makes it a lunar satellite. This was a extremely critical manoeuvre that involved realigning the orbiter and also firing its retro-thrusters for a period of 800 seconds.
The speed of the orbiter would now be reduced from about 2 km/sec to about 1.5 km/sec.
In its path to the moon, lunar gravity would have begun to dominate the probe at a distance of around 60,000 km from the moon. This distance would have been reached around midnight Friday. The moon's gravitational pull would have begun to add increasing velocity to the satellite. In order to exit the earth's gravitational pull and be enslaved by lunar gravity the satellite required to be slowed down.
It is this function that would have been performed this evening when its current trajectory would have brought the Chandrayaan to within 500 km of the moon, just above the lunar north pole.
This was the most critical time for the lunar probe as a number of factors would have come into play simultaneously. At this point, the satellite's orientation is earth-facing and it was no longer in a closed elliptic orbit, but in an open hyperbolic one.
This was a critical moment, for if velocity was not reduced at the correct time, the lunar probe will escape moon's gravity and be lost in space irretrievably.
At the moment details are awaited.
