An orbital change extends the life of India’s Mars orbiter


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An orbital maneuver has allowed India’s Mars Orbiter Mission avoid an eight hour period with no sunlight — thus draining its batteries — so that the mission can be extended until 2020.

The on-board battery which was to take over had a life of just about 1.4 hours, while the eclipse was to last for 8 hours. The spacecraft’s future was bleak.

The scientists thought of a solution. On the night of January 17, a team of eight engineers at Indian Space Research Organisation’s Telemetry, Tracking and Command Network, Bengaluru, sent a time-delayed command to the Mars probe. The command set in motion firing of eight on-board thruster rockets. Each of them were fired for 431 seconds, pushing the Mars Orbiter Mission (MOM) space probe to a new orbit that completely avoids an eclipse up to September 2017. The shadowing in September is of a smaller duration, which the satellite’s batteries can handle. “Because of the crucial orbital change, the MOM now gets three additional years’ life. We are expecting it to transmit data till 2020,” Isro chairman A S Kiran Kumar told DH.

The mission’s science data is not as important as the experience it is giving Indian engineers in operating a planetary probe remotely from Earth. This success speaks well for the future of India’s space effort.

3 comments

  • Gealon

    Not that I want to bash India’s program, I’m glad they are in the Mars game, but why the heck would they design and build a spacecraft with a non-rechargeable battery? It’s good that they altered the orbit and avoided draining their battery but why was this a problem to begin with? They’ve been launching for years now and something reliable like nickel-hydrogen cells should be easy enough to build or procure. I can only assume it was a measure to simplify the design that came back to bite them in the rear. All the best to them though.

  • Edward

    Gealon,
    My reading is that the battery is rechargeable, but it is not able to provide power for the duration of the flight through shadow (cool spacey word: umbra). Larger batteries weigh more, and that would reduce the mass for their experiments, so the trade-off seems to have been to carry a smaller battery pack and then keep out of Mars’ umbra for extended periods of time.

    MOM has a highly elliptical orbit, with a periareion* of 400 km and apoareion of 77,000 km, so it spends a lot of time far from Mars’ surface. It would be during one of these times that it would spend too much time in the umbra. The article did not say whether the spacecraft changed the orbital plane to prevent the orbit from passing through the umbra at that time (I think this is not so likely) or changed the orbital period in order to be in a different part of the orbit when the umbra passes through the orbital plane (more likely).

    * At the risk of being didactic, here are more cool spacey words: apoapsis and periapsis are the generic terms for apogee and perigee. The “gee” suffix designates that the orbit is around Earth, whereas the suffix “areion” is for orbits around Mars. A couple of weeks ago, one commentor here used the terms apohelion and perihelion. Here is a list of common suffixes for various bodies/objects:
    https://en.wikipedia.org/wiki/Apsis#Terminology_graph

    However, if you do not have that list handy while you are talking techie orbital mechanics, the generic apoapsis/periapsis are just fine, and you can almost always get away with using apogee and perigee for any body, which are even easier to remember.

    End of obsessive compulsive didacticism.

  • Gealon

    Thanks for the information Edward. I did think it odd that they would build a spacecraft without rechargeable batteries. The days of silver/zinc single use batteries in spacecraft are long long over.

    As for maneuver, I would change the orbital plane. Given the long elliptical nature of the orbit, it should be the maneuver that would consume the least fuel. And yes, my preference if for using Apoapsis and Periapsis.

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