Today at 16:03 GMT, teams of scientists from the European Space Agency celebrated as the news came in that the Rosetta spacecraft’s Philae lander probe had successfully touched down on Comet 67P.
After 10 years’ travel from Earth and three months in orbit around the comet, today was the day that Philae was due to break free from Rosetta and touch down on the comet. The landing site was chosen in September after just 6 weeks in orbit, based first on the feasibility and then on the scientific desirability of the possible sites. The physical nature of the landing site, including the presence of large boulders or crevasses, was important, as well as the slope of the surface and orientation of the lander, and it also needed to have the right balance of comet day and night for the lander’s scietific instruments.
In the weeks following the selection of the site, Rosetta moved to a distance 10km from the comet to allow for further close-up study, before moving away to a more distant trajectory ready for Philae’s deployment. The separation was confirmed at 09:03 GMT, and the 7-hour descent was begun.
At 16:03 GMT the news came from Philae that it had landed successfully on the comet, and the lander’s instruments seemed to be in good order. When it reached the surface, it was supposed to fire harpoons into the ground underneath it to anchor it to the comet, but they did not fire, and ESA Operations scientists and engineers are working to find out why.
Philae will conduct its primary science mission over the next few days, taking both panoramic and microscopic images, analysing the gas, taking measurements of the surface properties, as well as measuring the properties of the centre of the comet. If possible, with illumination conditions allowing, an extended phase of science operations could follow, until eventually, with the comet’s approach toward the Sun, the temperature inside the lander will become too hot for it to continue to operate.
In the meantime, we can be amazed by the acheivement of the engineers involved and enjoy the picture postcards sent to use from 67P.