When ISRO scientists handling the post-launch operations of the Mars orbiter push it into a certain critical planned position on Saturday morning, they expect to get a helpful little pull, from none other than the Moon.

November 16, around 2 a.m., is when the craft is due to get its orbit raised for the fifth time and also the last time near the Earth. (ISRO discounts the November 12 correction as a supplement of the fourth operation.)

That day’s target is to stretch the orbiter’s elliptical orbit to about 1.92 lakh km at its farthest yo-yo point (apogee) from the Earth. According to ISRO Chairman K. Radhakrishnan, during Saturday’s exercise, his team must also orient the spacecraft correctly and speed it up further in preparation for the big day of departure — December 1.

“We have to get the right condition on that day - the big orbit of 1.92 lakh km and the right inclination needed for the Mars transfer. The required inclination will automatically come from the effect of Moon. Once you cross 66,000 km you are closer to Moon, which becomes one of the pulling forces, and correct the inclination,” he told The Hindu.

The spacecraft, at its current maximum distance of 1.18 lakh km, already feels the lunar charm. Later, as it progresses beyond 9.25 lakh km, “Other planets will put in their influences but all that will come after a few days into December,” he said adding that such planetary pulls and pushes were accounted for during space travels.

ISRO has factored the lunar tug into its Mars travel numbers. The Moon was the first goalpost when India began its celestial adventures in 2008 with Chandrayaan-1.

In the next few days through November 30, some payloads or instruments on the orbiter are to be switched on as part of trials.

After about a week, the craft is expected to send in its first pictures.

While the spacecraft is still in the Earth’s orbit, Dr. Radhakrishnan said, the payloads would be checked once. “Some sensors must be tested, some calibrations must be done. Our people are finalising the requirements – such as position, altitude of the orbiter, Sun - and how and when to do them. Some pictures will also be taken. You may have to tilt the satellite for certain observations.”

Between now and November 30, the spacecraft, about the size of a small hatchback car, will circle our planet for the last few times.

It is slated to be put on the path to the red planet on December 1.

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