Orbiter on Track, Course Correction Call in August

The ISRO top brass is expected to finalise by early August whether or not to perform a third Trajectory Correction Manoeuvre (TCM).

CHENNAI: The Indian Space Research Organisation (ISRO) has every reason to be pleased with the performance of its ambitious Mars Orbiter Mission. The Mars Orbiter has completed 480 million km of its 680 million km journey to the Red Planet, and has been sticking to its planned trajectory with great precision.

The ISRO top brass is expected to finalise by early August whether or not to perform a third Trajectory Correction Manoeuvre (TCM).

The Mars Orbiter had blasted off from the spaceport at Sriharikota on November 5, 2013, and had undergone the first of its four planned TCMs on December 11. ISRO had decided that the second TCM, planned for April 2014, was not necessary in view of the precision with which the spacecraft was sticking to its planned trajectory.

The second TCM had been performed on June 11, and has been termed a “minor correction” by ISRO scientists. The manoeuvre had entailed the firing of the spacecraft’s smaller 22 Newton thrusters for 16 seconds, adding an incremental velocity of 1.574 m/s.

“We have now started preparations for the third TCM, and are monitoring the trajectory of the craft 24x7,” said S Arunan, Project Director of the Mars Orbiter Mission. “We had performed the second TCM as the geometry of the solar system is not going to change much. If the attributes change because of the gravitational pull of other planets or any other factors, then another TCM would be necessary. If the craft remains within the target corridor, then we might not require another TCM,” he added.

The target corridor has been fixed at 500 ± 50 km, and the Mars Orbiter has so far remained well within this band across its journey. Arunan said the spacecraft is presently at a radio distance (straight-line distance) of 130 million km, and that communication signals take about seven minutes to travel one way.

When the spacecraft reaches Mars orbit on September 24, it is expected to be at a radio distance of about 225 million km, and the communication delay may reach 20 minutes.

ISRO intends to insert the Mars Orbiter into a neo-elliptical orbit around Mars. This is scheduled for September 24. If it succeeds in this ISRO would become the first space agency in the world to have executed a successful Mars mission on its very first attempt.

The mission has pushed the boundaries of ISRO’s technological capabilities, primary among them being the autonomy of the Mars Orbiter.

The successful performance of this system so far hold promise of its use in other satellite systems that ISRO would be sending up in coming years.

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