The European Space Agency has conducted deeper analysis of just what happened to the Philae lander during its descent to Comet 67P/Churyumov-Gerasimenko and now believes the craft bounced off the wandering rock three times, not twice as was previously thought to the be case.
The new analysis re-tells the now-familiar story of Philae's descent: all went well for the first seven hours, during which time the probe rotated about once every five minutes. Next came first the bounce, which increased the rate of spin to one rotation every thirteen seconds.
The new analysis suggests that about 45 minutes later, between the first and second bounces, Philae “is thought to have collided with a surface feature, a crater rim, for example.” This touch slowed the craft's rotation to about one revolution per 24 seconds.
Evidence of this encounter with 67/P comet is advanced by Hans-Ulrich Auster from the Technische Universität Braunschweig, Germany, one of the principal investigators of the Rosetta Lander Magnetometer and Plasma Monitor onboard Philae (ROMAP) instrument the lander lugged. “It was not a touchdown like the first one, because there was no signature of a vertical deceleration due to a slight dipping of our magnetometer boom as measured during the first and also the final touchdown," Auster says. “We think that Philae probably touched a surface with one leg only – perhaps grazing a crater rim – and after that the lander was tumbling. We did not see a simple rotation about the lander’s z-axis anymore, it was a much more complex motion with a strong signal in the magnetic field measurement.”
About 55 minutes later Philae made what was previously considered its second bounce, before reaching its current position about six minutes later.
If Philae did indeed graze 67/P, it's even more remarkable that all its instruments survived its journey to the comet, even if the lander came to rest in a spot where it cannot see the sun often enough to keep operating.
Just where Philae's last landing took place remains unknown: the OSIRIS camera and CONSERT radio experiment haven't reported any new findings since November 21st. ®