Chandrayaan manoeuvre today

A crucial manoeuvre, to be performed on Saturday, on Chandrayaan-1 will inject it into an orbit around the moon from its current highly elliptical orbit around the earth.
On November 4, the last of the earth-bound manoeuvres was carried out, which put the satellite into an orbit with an apogee (the farthest point in the orbit from the earth) of 3,84,000 km and a perigee (the nearest point) at 1,019 km. With this apogee, the satellite actually encircles the moon as well. However, this earth-bound orbit is actually at about an inclination of 18 degrees to the earth’s Equator. Since the final designated lunar orbit is a circumpolar one, this orbit has also to turn around by almost 90 degrees.
As the satellite cruises along its present trajectory, the moon’s gravity will begin to dominate when this orbit will be about 60,000 km from the moon, which is expected to happen around midnight on Friday. Under the gravitational pull, the satellite will also begin to gain velocity. The orbit plane will also begin to gradually tilt away from its present near-equatorial one.
To enable the satellite to be completely captured by the moon, and thereby make the earth’s gravity irrelevant, the satellite would have to be slowed down. And this important operation will be performed when it is about 500 km from the moon, above the lunar north-pole. This is expected to occur around 1730 hrs on Saturday. At this point, the satellite’s orientation will actually be earth-facing. Also, significantly, the orbit will no longer be a closed elliptic one; it becomes an open hyperbolic one. So, if velocity reduction is not achieved at the designated time, the satellite will escape from moon’s gravity and be irretrievably lost in space. Thus, this operation is extremely crucial.
To enable Chandrayaan-1 to be captured by the moon, its orientation will be turned around by 180 degrees with the help of on-board reaction wheels. After this , retro-rockets will be fired for about 800 seconds.
The firing will give momentum to the satellite in the direction opposite to its orbit direction and slow it down. This will bring down its velocity from about 2 km/s to about 1.5 km/s.
It will then be under the total influence of the moon and its trajectory under its gravitational pull at this point will be such that the slowly tilting orbit would have actually swung by nearly 90 degrees southwards to become a circumpolar one. In this Lunar Orbit of Injection, the satellite’s closest point from the moon (perilune) is 500 km and the farthest point (apolune) is about 7,500 km. The period of revolution around the moon will be about 10 hours.
The preparation for the manoeuvre is expected to begin around noon on Saturday when satellite health checks will be performed. A little before the satellite approaches the lunar north-pole, its orientation will be turned around to ensure that its new orientation is exactly opposite to its velocity vector. The firing of the retro-rockets is expected between 1730 hrs and 1800 hrs. Within an hour, one will know if the manoeuvre has been successful.
Once completed, the orientation will be maintained such that the solar panel continuously faces the sun to generate maximum power. It will be similarly turned around every time a velocity reduction operation is to be performed. Four more velocity reduction operations are required to be carried out, twice at perilune and twice at apolune, to bring it into final pole-to-pole circular orbit of 100 km radius. The satellite will attain its final orbit on November 15.