Philae scientists reveal reasons for bumpy landing on comet

The reasons why the Philae lander bounced rather than fixed itself to Comet 67P have been revealed by flight controllers of the Rosetta satellite mission.

They have also shown in a video how the lander twisted and turned as it bounced along the comet’s surface before finally coming to rest.

Even though the lander has been almost silent since its primary battery ran out last November, the Philae team remain hopeful they will manage to wake it up.

The satellite has been an outstanding success since it went into orbit around the comet in August 2014.

Its onboard instruments have captured a wealth of data that is helping scientists to understand the icy objects that travel in from beyond the solar system.

Philae detached from Rosetta on November 12th, 2014, and headed down for a soft landing on the comet.

Initially it captured close-up pictures and sampled gases close to the surface, relaying data back to the orbiting Rosetta before its touchdown.

However, it didn’t attach itself to the surface as planned, despite having three ways to grab hold.

It had “ice screws” ready to burrow in if the surface was soft, but the surface was hard and the screws couldn’t break it.

It had harpoons set to blast into the surface as soon as the feet touched down.

It also had a thruster on its top to press downwards when the harpoons fired.

Neither the harpoons nor the thruster worked and Philae rebounded from the surface because of the comet's weak pull of gravity.

Animation

The blend of animation and video shown by the flight controllers was based on detailed data that described how Philae tumbled and hit the surface several times.

It finally came to rest at the foot of an incline that left Philae’s solar panels mostly in the shade and unable to recharge the primary battery.

Some limited charging of the secondary batteries allowed eight intermittent contacts in June and July this year as the comet got closer to the sun, but there has been nothing since.

The Philae team at the DLR Lander Control Centre in Cologne believe contact might be possible.

The scientists may try and fire the harpoons again if any intermittent contact can be made.

However, the scientists are racing against time, with the comet now heading out beyond the orbit of Mars, with temperatures falling.

"We think we have until the end of January before the lander's internal temperature gets too cold to operate. It cannot work below -51 Celcius," said Koen Geurts, Philae's technical manager.