Mars Orbiter Mission passes by penultimate perigee

Will walk around Earth for the last time over the next 4 days

The Indian Space Research Organisation (Isro) today said the Mars Orbiter Mission (MOM) has just passed by its penultimate perigee.

This means that MOM will walk around the Earth one last time- in its last orbit over the next four days and leave for Mars on Saturday night.

The spacecraft has been in Earth-bound orbits with different apogees since its launch on November 5.

On 1 December, the Trans-Mars Injection will take place at 00:49 hrs. This will be achieved by a complex combination of navigation and propulsion technologies, governed by the gravity of Sun and Mars, and assisted by the 440 N Liquid engine. Further fine tuning of the trajectory will be done using the Attitude and Orbit Control Thrusters during the Trajectory Correction manoeuvers planned en route.

The December 1 operation would impart a specific velocity to the spacecraft so in September the spacecraft reaches close to Mars (500 km, +/-50).

“The crux of the success of the operation on December 1 is we should be able to estimate precisely the velocity, and the time we need to impart the velocity to the spacecraft so it takes that position. In that, the computation of the spacecraft navigation is important: How it passes from the sphere of influence of the Earth and enters a heliocentric orbit,” said Chairman K Radhakrishnan.

On September 24, Isro would have to reduce the velocity. “If we are able to reduce the velocity precisely at that point, we will get the orbit and, finally, the instruments will be operated.”