WASHINGTON: Philae spacecraft is successfully on its way to attempt the first-ever landing on the surface of a comet.
The separation was confirmed at 9.03am GMT today (Wednesday), with pictures of Philae approaching the comet expected throughout the day before it lands on the surface at 3.30pm GMT.
A faulty thrusters and a computer glitch both threaten the success of the mission – but scientists at mission control have confirmed a daring attempt to land on the comet using the harpoons on the Philae lander will still be made.
This morning it was revealed that the cold thrusters positioned on top of the Philae lander was not working properly. The cold thrusters is used to push Philae closer to the comet.
Without it, it will have to rely on its three landing screws and two harpoons to successfully attach itself to the comet’s surface. Despite the potential obstacles, the fourth and final ‘go/nogo’ was been given, meaning the landing would be attempted as scheduled. At 06.30am GMT this morning Rosetta completed a complex trajectory manoeuvre to get it on a direct angle towards the comet. Before Philae’s release, Esa said there was ‘no going back’.
At 08.35am GMT the team in Darmstadt, Germany, sent a command to release the Philae probe from Rosetta’s grip. The probe will then be in free fall for seven hours, before landing on the icy surface of comet 67P/Churyumov-Gerasimenko. According to Esa, during checks of the lander’s health, it was discovered that the active descent system could not be activated.
However, if the thrusters is reactivated and all goes to plan, at touchdown a landing gear will absorb the force of the landing. Ice screws in the feet and a harpoon system will lock to the comet’s surface and the thrusters will push it down into the surface to counteract the impact of the harpoon. But without it scientists will be forced to rely fully on the harpoons.
‘The cold gas thrusters 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.’
Philae will touch down at a sight called Agilkia, previously known only as ‘Site J’. Philae’s cold thrusters is a nitrogen-powered and is designed to fire on landing in order to prevent the probe from flying off into space due to the comet’s weak gravity.
In order to prepare cold-gas jets, scientists use one of two pins to puncture a wax seal on the thruster’s gas tank. Experts detect success by the change in pressure in the piping system. However, this morning mission controllers did not see pressure increases after two attempts with each of the two pins. But according to the industry provider, there may still be a chance that retrying the puncture of the wax seal would succeed, even after four failed attempts.
Philae must now rely on its two harpoons and ice screws to hold it to the surface. Whether that will be enough – or whether the lander will bounce off before they can secure it to the surface – remains to be seen. If all goes to plan, Philae should send a signal back to mission control engineers at around 4pm GMT.