Following a night of critical Go/NoGo decisions, Rosetta and Philae are cleared for separation, despite a problem onboard the lander. The mission is set to become the first in history to touch down on a comet.
During checks on the lander’s health, it was discovered that the active descent system, which provides a thrust to avoid rebound at the moment of touchdown, cannot be activated.
At touchdown, landing gear will absorb the forces of the landing while ice screws in each of the probe’s feet and a harpoon system will lock Philae to the surface. At the same time, the thruster on top of the lander is supposed to push it down to counteract the impulse of the harpoon imparted in the opposite direction.
“The cold gas thruster on top of the lander does not appear to be working so we will have to rely fully on the harpoons at touchdown,” says Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center.
“We’ll need some luck not to land on a boulder or a steep slope.” “There were various problems with the preparation activities overnight but we have decided to ‘go’. Rosetta is lined up for separation,” says Paolo Ferri, ESA’s head of mission operations.
The final manoeuvre by Rosetta was conducted at 07:35 GMT / 08:35 CET, which is taking Rosetta to a point about 22.5 km from the comet’s centre for separation.
After separation, we will not hear from Philae for some two hours until the lander establishes a communication link with Rosetta. Philae cannot send its data to Earth directly – only via Rosetta.
The descent to the surface of Comet 67P/Churyumov–Gerasimenko will take around seven hours, so confirmation of a successful touchdown is expected in a one-hour window centred on 17:02 GMT / 18:02 CET.
Journey to a comet and sience on the surface – European Space Agency, ESA
“We are anxious but excited,” said Jean-Pierre Bibring, lead lander scientist, during this morning’s press briefing. “It is not every day that we try to land on a comet.”
Follow the event live via www.esa.int/rosetta