Scientists raise Mars spacecraft’s orbit

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CHENNAI/BANGALORE, November 7:   The Indian Space Research Organisation successfully boosted the orbit of its Mars spacecraft, firing the engine onboard in the early hours of Thursday.

After scientists sent a command from the ISRO Telemetry, Tracking and Command Network in Bangalore, the 440-Newton engine throbbed with life for seven minutes from 1.17 a.m., raising the Mars orbiter’s apogee from 23,566 km to 28,825 km and perigee from 247 km to 252 km.

ISRO scientists sent the command for firing the engine from the state-of-the-art ISRO Telemetry, Tracking and Command Network (ISTRAC) situated in Bangalore.

This is the first of the six tricky orbit-raising manoeuvres that the ISRO will perform as its spacecraft spins around the earth in the next 25 days.

The second manoeuvre will take place in the early hours of Friday.

The sixth and last operation will be done on December 1 to shoot the orbiter, launched on Tuesday, out of its earth-orbit into a sun-centric orbit. From then on, the spacecraft will coast around the sun for 300 days before the ISRO tries to capture it on the Martian orbit on September 24, 2014.

The ISRO’s Polar Satellite Launch Vehicle (PSLV-C25) on Tuesday (November 5, 2013) put the orbiter into an earth-bound orbit with a perigee of 247 km and an apogee of 23,566 km.

ISRO Chairman K. Radhakrishnan told The Hindu on Thursday that the liquid engine was fired for seven minutes.

“At 2.15 a.m. tomorrow [Friday], we will fire the engine again for about 582 seconds, almost 10 minutes, and we will raise the apogee to 40,000 km from the earth,” he said.

From the first manoeuvre, the scientists gained information about how long to fire the engine to give the necessary velocity to the spacecraft, he said.

“Our focus was on the performance of the LAM [liquid apogee motor that is fired for orbit corrections.] After the first liquid engine firing, we know the specific impulse, and how many seconds to fire for achieving a certain velocity for the orbiter.”

Friday’s firing is designed to raise the apogee to 40,000 km. The third consecutive manoeuvre is planned for 2.15 a.m. Saturday to increase the apogee to more than 71,000.

Over the next days, the five instruments will be checked and calibrated for the first time in space.

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