US, Indian probes prepare to go into Mars orbit

On September 22, the Mars Orbiter is scheduled to fire its main engine

September 17, 2014 10:46 pm | Updated November 01, 2016 09:07 pm IST

Scientists and engineers from the Indian Space Research Organisation (ISRO) monitor India's Mars Orbiter Mission (MOM) at the ISRO Telemetry, Tracking and Command Network (ISTRAC). Photo: K. Murali Kumar

Scientists and engineers from the Indian Space Research Organisation (ISRO) monitor India's Mars Orbiter Mission (MOM) at the ISRO Telemetry, Tracking and Command Network (ISTRAC). Photo: K. Murali Kumar

On Monday (Sept. 22), two spacecraft that are nearing Mars, one American and the other from India, will fire their engines and undertake crucial manoeuvres.

Shortly after 7 am on that day by Indian time, America’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) will ignite its six main engines, which will then burn for 33 minutes to slow the spacecraft and put it in an elliptical orbit around Mars. In subsequent manoeuvres, its orbit will be trimmed so that the probe flies 150 km above the planet at its closest point and about 6,300 km at its farthest.

These are familiar operations for the U.S. space agency, NASA, which has successfully sent more than a dozen spacecraft to Mars, including landers and rovers. Even so, Americans have known failure too, with three of their missions being lost either en route to the planet or on arrival there, and will doubtless be hoping that the newest voyage goes without any major hitch.

But for the Indian Space Research Organisation (ISRO), sending its first mission to the Red Planet, it is all very new and so the tension and worries will be far greater.

For one thing, the main liquid-propellant engine aboard the Mars Orbiter, which has not operated for nearly 300 days since the spacecraft left Earth on December 1 last year, must function as expected to put the probe into its intended orbit (see “Trusty engine on Mars Orbiter to be tested yet again,” The Hindu , Sept. 11).

Besides, with about a 12-minute time lag in communications between ground stations on Earth and the probe, the spacecraft has to be programmed in advance to autonomously execute various operations to put it into orbit around Mars. There are bound to be concerns over whether the proper commands have been uploaded to the orbiter.

At about 2.30 pm on Monday, the Mars Orbiter is scheduled to fire its main engine for nearly four seconds. This will test how well the propulsion system is functioning and also provide a final trajectory correction.

Two days later, at about 7:17 am on Sept. 24, the orbiter's engine will commence the burn to take the spacecraft into orbit about Mars according to the timeline prepared by ISRO.

But little over four minutes into an engine firing that is expected to last about 24 minutes and 14 seconds, the spacecraft will slip behind Mars (as seen from Earth) and go out of communication contact.

The data from those four minutes or so of firing, relayed back by the probe, will begin to reach ISRO’s mission controllers at 7.30 am. This information will let them gauge whether the engine has begun operating as planned.

The spacecraft will stop the engine when onboard sensors indicate that its velocity has been reduced by about 1.1 km per second. The burn will end while the spacecraft is still behind Mars. Data transmitted by the probe after it emerges into view of Earth will be received by mission controllers at about 8 am.

Around 8:05 am or 8:10 am, “we will be able to say [if] we [the orbiter] are going around Mars,” said V. Koteswara Rao, ISRO’s Scientific Secretary. The spacecraft must be tracked for a further period of time to establish its orbit parameters and that information was expected to become available only by afternoon.

The Mars Orbiter’s planned orbit around Mars is 423 km by 80,000 km.

There are moves afoot for ISRO and NASA to work with one another and share data from their respective Mars probes.

The U.S. space agency is in discussions with ISRO over potential scientific collaboration, said James Green, a senior agency official, in testimony before a Congressional subcommittee last week. With the data collected by MAVEN and the Mars Orbiter, “NASA and ISRO scientists will have a wealth of information to help solve mysteries regarding the Mars atmosphere,” he observed.

In addition, the two space agencies are talking about setting up a Joint Mars Working Group to coordinate their plans for studying the planet, Dr. Green remarked.

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