Mars spacecraft cruising towards sun-centric orbit

ISRO scientists and engineers monitor the Mars Orbiter Mission (MOM) at ISRO Telemetry, Tracking and Command Network (ISTRAC) Mission Operations Complex (MOX) tracking centre, at Peenya, in Bangalore. File photo: K. Murali Kumar  

With India’s spacecraft to Mars slung out of its earth-bound orbit early in the morning of December 1 and its cruising towards the sun-centric orbit, its 300-day voyage to the Red Planet has begun. The Indian Space Research Organisation (ISRO) accomplished this tricky manoeuvre called Trans-Mars Injection (TMI) of the spacecraft by giving commands to the spacecraft’s propulsion system to start firing at 00.49 hours Sunday (December 1). The propulsion system came up with a cameo performance for 23 minutes, imparting the required velocity to the spacecraft, which was catapulted out of its earth-bound orbit into the sun-centric phase. Eight control thrusters on board also erupted into life, aiding the propulsion system to give the needed velocity to the spacecraft. “The spacecraft is now on course to encounter Mars after a journey of about 10 months around the Sun,” said an ISRO statement. The orbiter is now in a hyperbolic orbit and it will escape from the sphere of influence (SOI) of the Earth around 1.15 a.m. of December 4. The SOI of the Earth extends to about 9.25 lakh km from the Earth.

According K. Radhakrishnan, ISRO Chairman, the TMI was a “crucial” manoeuvre because the spacecraft needed to be given the exact velocity to push it out of the earth-orbit, make it escape from the SOI of the Earth, then make it coast around the sun for about 300 days and ultimately insert the spacecraft into the Martian orbit on September 24, 2014.

On that day, the propulsion system will be fired again after it has idled for 300 days during its voyage in deep space. This ignition will lower the spacecraft into the Martian orbit.

Orbiter heading out of Earth’s sphere of influence

With the successful completion of the Trans-Mars Injection procedure by the ISRO, the earth’s dominance over the Mars orbiter is set to end.

S. Arunan, Project Director, Mars orbiter, ISRO, said on Sunday afternoon that after the successful firing of the spacecraft’s 440 Newton engine, “the spacecraft has gone into a highly hyperbolic orbit, it will leave the SOI (sphere of influence) of the Earth and enter into a perfectly sun-centric orbit.”

“The velocity required for the spacecraft to escape from the earth’s gravity has been provided to it and it will escape from the SOI of the Earth with a perfect sun-centric elliptical orbit,” Mr. Arunan explained.

M. Annadurai, Programme Director, Indian Remote-sensing Satellites and Small Satellites Systems, ISRO, said the total velocity given to the spacecraft at the end of 23 minutes of firing of the 440 Newton engine including the previous firings was 11.4 km per second. The spacecraft would travel 3.5 lakh km in 24 hours after the accomplishment of the TMI and it would cross the SOI of the Earth 72 hours after the TMI, Dr. Annadurai said.

“The health of the spacecraft’s system including its main and redundant systems are all right,” Mr. Arunan said. “The orbiter’s health is normal. It is in a perfect hyperbolic orbit now. It means the orbit is open. There is no ending. There is no apogee,” he explained. After the ground station at Canberra, Australia, acquired the spacecraft and started tracking it soon after the TMI was achieved, the Goldstone Deep Space Communications Tracking Station in the U.S. and the Indian Deep Space Network (IDSN) at Byalalu village, near Bangalore, would start tracking it. The IDSN at Byalalu has an 18-metre and 32-metre dish antenna to communicate with the orbiter. The medium-gain and the high-gain antenna on board the spacecraft would be used to communicate with it from the ground stations.

The spacecraft, which weighs 1,350 kg, carries 850 kg of fuel. About 198 kg of fuel were used for firing the 440 Newton engine for 23 minutes.

ISRO engineers said they were “bugeting” the fuel in a judicious way for three mid-course corrections of the spacecraft’s trajectory and its insertion into the Martian orbit on September 24, 2014.

Our Bangalore correspondent adds:

Set to cover a million km a day

As it hurtles towards its planetary goalpost on a path of 680 million km, the Mars Orbiter will cover one million km each day, according to S.K. Shivakumar, Director of the ISRO Satellite Centre, which made the 1,330-kg satellite.

The spacecraft has been designed to travel over 300 days and take a path half way round the Sun. Ground controllers expect to make four ‘course corrections’ to keep it on the right track.

The first one is likely on December 11, or a couple of days later, ISRO Scientific Secretary V. Koteswara Rao said at a a recent briefing. “During the journey, if the spacecraft makes any minor deviations from the path, we have to make corrections. One will be on December 11, another in April 2014, the third in August 2014, and the last one will be on September 14, 10 days before we insert it into the Martian orbit.”

The ultimate test will be the Martian orbit insertion, planned for September 24 next. It will be done by slightly breaking the spacecraft’s speed through an engine burn. It will then start orbiting the Red Planet elliptically.

The spacecraft will be among Earthly friends when — or if — it reaches the barren Martian environment.

Two rovers and three orbiters of two other space agencies are already probing untold Martian mysteries. Four of them are from NASA, whose latest orbiter mission MAVEN left on November 18 and is also on its way there. MAVEN (Mars Atmosphere and Volatile EvolutioN) is designed to be near Mars two days ahead of the Indian spacecraft.

NASA’s rover Opportunity has been digging around since it landed on the Martian surface in 2004. It was joined by the iconic Curiosity robotic laboratory in 2012. Then there are two active NASA spacecraft, the Mars Odyssey (2001) and the Mars Reconnaissance Orbiter (2005), apart from the Mars Express sent by the European Space Agency in 2003 — all of which are circling Mars.

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