India’s first interplanetary mission would be completing its 100 day in space, on Wednesday. The landmark Mars Orbiter Mission, which blasted off from Sriharikota on November 5, 2013, has travelled 190 million kilometers so far. A statement from ISRO has said the mission is in the pink of health and performing in line with the preset parameters.
The Mars Orbiter Mission would have to travel 490 million kilometres more before it can be injected into orbit around Mars. This landmark event is scheduled for September 24, 210 days away. If successful, the Indian Space Research Organisation (ISRO) would become the first space agency to get a spacecraft into orbit around Mars in its very first attempt. The Mars Orbiter Mission is already substantially further out in space than ISRO has ever gone before.
The large distance between the Mars Orbiter Mission and the Earth has meant that the communication signals, carrying commands and information between Earth and the spacecraft, are not instantaneous. The communication delay is presently at 55 seconds one way. The spacecraft is controlled from the ISRO Telemetry, Tracking and Command Network (ISTRAC), located outside Bangalore.
ISTRAC has so far performed one of the four planned Trajectory Correction Manoeuvres (TCM). The TCMs are aimed at giving the spacecraft the requisite attitude (direction of heading) and delta-V (incremental velocity to keep it on the requisite orbit). The first TCM was performed successfully on December 11, 2013, and three others are to be carried out this coming April, August and September.
The February 6 operation also saw ISTRAC push the five scientific instruments aboard the Mars Orbiter Mission into full action, to check if they were in good health. The ISRO statement said all five instruments are normal. The instruments aboard the Mars Orbiter Mission have been tested before, on November 20, 2013. The spacecraft had transmitted images on the Earth, which ISRO had then made public.
The most critical factor to the success of the Mars Orbiter Mission, according to ISRO scientists, would be the firing of the main propulsion engine to insert the spacecraft into Mars orbit. The engine would have, by that point, been dormant for 10 months, and this is a technological challenge that ISRO has never faced before. The TCMs are being performed using the attitude thrusters, and not the main engine.
Also, the Mars Orbit Insertion (MOI) would be different from what the spacecraft has achieved so far. All manoeuvres so far have been aimed at giving the craft more thrust. The MOI would see the engine decelerate the craft, to bring it down to a speed suitable for orbit around Mars. This is required as the Hohmann Transfer Orbit, which is the method used to get spacecrafts to other planets, has put the Mars Orbiter Mission on an elliptical orbit around the Sun with the aim of making its path cross that of Mars.
The craft velocity of orbit around the Sun is much higher than that required for orbit around Mars. This would be why the engine would have to fired, for a change, to slow the spacecraft down, instead of making it go faster. ISRO has also said it has achieved a high degree of precision in the performance of most aspects of the mission so far, and that the hope was for this to continue.