News Space 06 September 2016

Rosetta finally finds comet-lander Philae


The lander has been located wedged in a crack on comet's surface weeks before mission ends.


How Philae was supposed to land on Comet 67P/Churyumov–Gerasimenko. Its landing gear was designed to absorb the forces of landing while ice screws in each of the probe’s feet and a harpoon system locked Philae to the surface. At the same time, a thruster on top of the lander was to push it down to counteract the impulse of the harpoon.
ESA/ATG medialab

The European Space Agency’s little comet lander Philae has been found wedged into a crack on Comet 67P/Churyumov–Gerasimenko.

Images of it were captured on 2 September by Rosetta’s high-resolution OSIRIS narrow-angle camera as the orbiter came within 2.7 kilometres of the surface.

Philae is upended with two legs pointing upwards, clearly explaining the difficulties in establishing communications after its landing on 12 November 2014.

“With only a month left of the Rosetta mission, we are so happy to have finally imaged Philae, and to see it in such amazing detail,” Cecilia Tubiana of the OSIRIS camera team said in a media release.

ESA’s Laurence O’Rourke, who has been coordinating search efforts for Philae, said he was “excited and thrilled” to finally get a picture of the lander.

Philae’s 1 metre-wide body and two of its three legs can be seen extended from the body. The Rosetta Navigation Camera image taken on 16 April 2015 is shown at top right for context, with the approximate location of Philae on the small lobe of Comet Churyumov-Gerasimenko marked.
ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA. context: ESA/Rosetta/NavCam

Philae was last seen when it first touched down.

Two malfunctions – one with the thruster on top of the probe, designed to push Philae onto the low-gravity comet, and one with the harpoons designed to anchor the craft to the surface – caused the craft to bounce off the surface twice.

The first bounce catapulted Philae more than a kilometre above the surface – it took two hours for it to float back down. It then bounced a second time before coming to rest a few minutes later.

It landed for the final time at a location later named Abydos, on the comet’s smaller lobe on its side with two legs on the surface and one pointing upwards, lodged against a cliff face. The harpoons for that leg did not fire.

Labels show what can be see of Philae’s features in this image taken by Rosetta’s OSIRIS narrow-angle camera image from a distance of 2.7 kilometres.
ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Philae's primary battery was exhausted within days and the lander went into hibernation.

It awoke briefly in June and July 2015 as the comet came closer to the Sun and more power was available.

“This remarkable discovery comes at the end of a long, painstaking search,” said Patrick Martin, ESA’s Rosetta Mission Manager.

“We were beginning to think that Philae would remain lost forever. It is incredible we have captured this at the final hour.”

On 30 September Rosetta will itself descend to the comet’s surface on a one-way mission.

In particular it will investigate open fissures on the comet’s surface that are hoped to provide more information on the interior structure of the comet.

  1. https://cosmosmagazine.com/space/rosetta-limit-what-humankind-can-do
  2. https://cosmosmagazine.com/space/philae-comet-lander-wakes-up-and-phones-home
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