Rosetta reaches perfect position to get touchy Philae

The European Space Agency's (ESA's) comet-catching Rosetta probe is “lined up for lander delivery”, after a couple of rocket nudges placed it into its penultimate pre-launch orbit for the attempt to release the Philae lander and send it to comet 67P/C-G.

ESA boffins report that late last week Rosetta fired a thruster for 90 seconds that took it further from the comet after a series of orbits saw it move within 10km of the celestial wanderer.

The Rosetta team says slightly more orbits are necessary because it allows the craft to achieve just the right speed for lander release. Any faster or slower and it will be too hard to drop Philae without also travelling to the night side of the comet, which mission control is keen to avoid. ESA boffins also feel that a lower orbit would mean “The time from last orbit control manoeuvre to touch-down would increase, thus increasing the time over which navigation errors would propagate, affecting landing accuracy.”

There are still a few manoeuvres to be made, however, as the diagram below shows.

The final approach plan for the Rosetta probe and Philae lander
Click here to embiggen . Image: ESA

The scary-looking burn will take place on November 12th, about two hours before Philae's release. The burn will put Rosetta in an elliptical orbit that brings it within 5km of the comet so it can release the lander. About 40 minutes after Philae drops, another burn will see Rosetta scoot out to a position from which it can see the lander below, presumably in order to pick up radio signals and beam back exciting images of comet 67P/C-G's surface.

Those images could be just ten sleeps away! Go you good things Rosetta and Philae! The Reg and all who read her wish you well! ®