Thursday, November 13, 2014

Landing a probe on a comet (67P/Churyumov-Gerasimenko)

The European Space Agency's Rosetta Spacecraft has succeeded in landing a device carrying instruments on the comet
The extent of success of the mission is not clear as I write this piece on Nov 13, 2014 as seen from this report:

According to TV news, gravitational acceleration at the place of landing is 100,000 times weaker than on earth; if this is true, it would mean that a 100 Kg lander would behave as if it weighed 1 gram! It is obviously a great challenge to a build a robotic device to work under such circumstances, land on a surface whose properties are not known, and then carry out useful research. All this has to be done with 64 hours of battery life! We do not know how well the solar panels would be able to recharge the batteries!  

The goal is undoubtedly a worthy one. We should recall the great contribution of Edmond Halley in this context. He predicted that a comet that had appeared in 1456, 1531, 1607, and 1682 would return in 1758. He did not live to see this happen, but the prediction made a big impact on human thought. Superstitious beliefs that comets were heavenly messengers foreboding pestilence, famine and death were shown to be hollow. His prediction was not a casual one. He had been attracted to Kepler's laws of planetary motion and was looking for proof that they were in fact accurate. In August 1684, he went to Cambridge to discuss this with Sir Isaac Newton, and found that Newton had solved the problem, working on the orbit of comet Kirch. Finding that Newton could not locate a record of his own work, Halley encouraged him to redo it and publish it. It finally came out prominently in “PhilosophiƦ Naturalis Principia Mathematica authored by Newton and published at Halley's expense in 1687.
Halley and Newton did not merely change our knowledge of mechanics. They helped destroy the cobwebs of the human mind, giving us an opportunity to develop a more verifiable world view. We don’t need to cook up myths to explain what we do not understand. We need to explore and find verifiable truths to share.

The European comet lander Philae is humanity’s latest step in this direction. As a robot it looks tragically ill equipped to search for the presence of amino acids on a 4 km rock floating hundreds of million miles away. It will no doubt inspire better robots to be built to explore heavenly bodies. The presence of certain amino acids on comets would tell us more about the origin of life. Any discoveries in this direction would take us farther along the revolution Halley and Newton had launched.  

Let us recognize the engineering challenges in this, and encourage students to design good robot explorers. It is not a job for a single team. Hundreds of ideas need to be explored and applied to solving hundreds of problems, apart from building comet explorers. I had written a piece on a related topic in 2012 and the URL for that is    

Srinivasan Ramani


Srinivasan Ramani said...

Philae sent a spectacular photo of its environment, but it seems to be perched precariously on two legs against a cliff that may deny the lander sunlight required to recharge its batteries. Visit

Visit the BBC webpage

Srinivasan Ramani said...
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Srinivasan Ramani said...

Philae has gone into hibernation. Mission control is hoping that as the comet gets closer to the Sun, the robot will get enough sunlight to recharge its batteries and come back to life.

Visit Time of India News Item