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Asian Tribune is published by World Institute For Asian Studies|Powered by WIAS Vol. 12 No. 2647

Tale of Comet Chasing: How European scientists made space History

Hemantha Abeywardena writes from London…

The scientists at the ESA – European Space Agency – made space history on Wednesday, when they at last managed to land the comet probe, Philae, on Comet 67P, an icy relic from the Big Bang, after chasing the former for almost a decade, since it left the Earth in 2004.

In terms of the vast distance covered by the mother-ship, Rosetta, which carried the probe up until Wednesday, the number of nations involved, and of course, the cost – over $1.5 billion – the statistics of the whole mission are breathtakingly staggering. Although, the finale was somewhat spoilt by two glitches propped up unexpectedly at the eleventh hour, the mission was a success, when the catalogue of hindrances that it surpassed is taken into account.

Comet 67P, discovered in 1969 by two Soviet astronomers, is en route towards the Sun in an elliptical orbit, as most comets do. Its shape is compared to that of a rubber duck by the scientists involved in the mission and to the most notable physical assets of Kim Kardashian, the US reality TV star, by those who want to sex up the tale of the mission. Both camp managed to make the grand finale on Wednesday, an exciting event, indeed – a classic case of end justifying means.

The scientists at the ESA decided to land a probe on a comet and launched Rosetta, the spacecraft that carried the probe, Philae, in 2004. Rosetta travelled for more than 10 years, while covering a vast distance of over 6 billion km to reach its target, Comet 67P, in September this year, when the former finally positioned itself in an orbit around the latter.

Chasing a comet, a lump of ice and dust, is not a cakewalk. One of the challenges, among so many, was powering Rosetta to reach a colossal speed to catch up with a fast-moving comet. The scientists ingeniously forced Rosetta, named after the famous Egyptian stone, into a few orbital manoeuvres between the Mars and the Earth, while making the former to use the combined gravitational pull of the both to achieve the difficult goal, which in the end resulted in bringing the spacecraft into an orbit of Comet 67P.

In September 2014, Rosetta managed to enter into an orbit around Comet 67P, while paving the way for its ultimate goal – releasing the lander, Philae, on the surface of the comet in November.

On Wednesday, Rosetta finally released Philae at 8.35 am GMT, much to the excitement of astronomers and space enthusiasts alike. Since the lander was millions of miles away from the Earth, even a radio signal, travelling at the speed of light, took almost half an hour to reach our planet, which, in turn had made the prompt earthly intervention next to impossible; the signal for the detachment reached the mission control in Germany at 9.03 am GMT.

Rosetta released Philae from a height 20 km, above the surface of Comet 67P. Since the gravitational pull of this particular comet was so feeble, the time for the vertical descent of the lander was estimated to be around 7 hours, which on the Earth would have taken a few minutes. The estimated time was 3.35 pm GMT on the same day and the lander did touch down the surface at that time, confirmation of which reached the earth with the anticipated time delay of around half an hour.

As soon as Philae was released from Rosetta, the mothership, the astronomers at the ESA found a major glitch, which had the potential to leave the entire exercise in complete jeopardy: the mechanism, known as thruster, the job of which was to provide the lander with an additional downward push just before the landing stopped working.
Philae was supposed to fire two harpoons into the surface of Comet 67P in order to anchor itself firmly to the ground. When it happens, a force of recoil - exactly as it happens to a gun, in the event of a bullet being fired – inevitably acts upon the lander upwards, which could push it a few kilometres back into space, rather than facilitating the landing.

Adding insult to the injury, the two harpoons failed as well in the last minute, which left the determination of the final outcome in the realm of luck rather than sphere of the laws of physics. Unfortunately, the luck on this occasion was not on the side of the moist-eyed astronomers of the ESA, who were broadcasting the various form of understandable jubilation and the fate of the Philae in equal measure.

Philae did land on the comet at the exactly estimated time and it was the first-ever comet landing. So, the Europeans scientists made space history, in that context. Since the lander could not anchor itself firmly to the surface of the comet, however, it bounced back into space twice before settling down on its side inside a cave. The awkward position sealed both the fate of Philae and that of the final goal of the mission, as its solar cells failed to get enough sunlight to power its instruments. On Saturday, the scientist confirmed that the batteries of Philae had finally run down.

Since comets were remnants of the solar systems at their early stages, scientists hope that they contain the mysteries of that time. In this context, the scientists at the ESA were eager to analyse the soil of the Comet 67P with the aid of the on-board instruments of Philae. Unfortunately, it did not work out as planned, much to the disappointment of the whole team.

They, however, still pin their hopes on Rosetta, the mothership, which still orbits Comet 67P. They hope Rosetta will be able to give more information on the impending, magnificent, structural spectacle of the comet en route to the Sun in the coming months from very close proximity, something that has been mesmerising the human beings since time immemorial.

All in all, the mission was a monumental achievement, despite the setback in its last leg. Our failure to conduct a scientific analysis on the surface of a comet, however, adds yet another intriguing aspect to these celestial objects, in addition to the catalogue of them that already exists.

- Asian Tribune -

Tale of Comet Chasing: How European scientists made space History
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