ISRO rehearses orbit-raising manoeuvres for Mars orbiter


It was a controlled exercise, says Programme Director

The Indian Space Research Organisation (ISRO) on Wednesday rehearsed a series of six manoeuvres, simulating the raising of the apogee of its Mars orbiter which the Polar Satellite Launch Vehicle (PSLV-C25) put into earth-bound orbit of 247 km x 23,566 km on Tuesday.

The rehearsal took place from the ISRO Telemetry, Tracking and Command Network (ISTRAC) station in Bangalore. These manoeuvres were rehearsed without actually firing the 440 Newton engine on board the Mars orbiter. In reality, the first of these orbit-raising manoeuvres will take place at 1.50 a.m. on Thursday and the last on December 1. Commands will go out from the ISTRAC station to the spacecraft to fire the 440 Newton engine for raising the apogee.

The engine will be fired when the Mars orbiter is at its perigee so that the apogee will become more elliptical. The D-day is on December 1 when a prolonged firing of the 440 Newton engine will catapult the Mars orbiter out of the earth-centric orbit into the sun-centric orbit. Then the orbiter will coast around the Sun for nine months and finally captured into the Martian orbit on September 24, 2014.

M. Annadurai, Programme Director, Indian Remote-Sensing Satellites (IRS) and Small Satellites Systems (SSS), ISRO, said on Wednesday, “We did the rehearsal of everything today in a controlled way except firing the engine and we have come back to the normal.” India’s Mars Orbiter Mission comes under the IRS programme. When the 440 Newton engine aboard the Mars spacecraft is fired on Thursday at 1.50 a.m, the apogee will be raised to 28,793 km. However, its present perigee of 247 km will more or less remain the same. “The six firings will be done when the orbiter is in the perigee. The whole sequence has been rehearsed. We monitored whether everything went well,” he said.

Spacecraft’s health normal

“The overall health of the spacecraft is normal. Systems on the orbiter such as gyros, accelerometer and star-sensors have been calibrated. In the spacecraft, everything is working normally,” Dr. Annadurai said. ISRO Chairman K. Radhakrishnan told a press conference at Sriharikota on October 30 that after the Mars orbiter’s apogee is raised first on November 7 to 28,793 km, the second firing of the engine will take place on November 8 early morning. This second firing will take the orbiter’s apogee to about 40,000 km from the earth. The third orbit-raising operation will take place on November 9 when the apogee will be boosted to about 70,656 km. The fourth orbit-raising operation will take place on November 11 when the apogee will reach about one lakh km. The fifth manoeuvre will be done on November 16 when the apogee will reach 1.99 lakh km from the earth.

Dr. Radhakrishnan added: “We will then a have a crucial event — the trans-Martian injection [of the orbiter] from the earth-orbit towards Mars, which will take place at 0042 hours on December 1. This is the immediate action programme for the Mars orbiter. We have a long voyage of 300 days.

On September 24, 2014, we are planning to have the Mars orbit insertion of the spacecraft. Once it is successfully done, we will go for the experiments.”

The orbiter has five scientific instruments for analysing the Mars’ surface features, to find out whether it has methane and to study its mineralogy and the atmosphere.

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Printable version | Jun 27, 2017 12:07:40 PM |