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New shots of Philae will help Rosetta scientists find where it landed

Elizabeth Howell, News Writer
Nov 18, 2014, 1:42 UTC

Sen—Although the Philae lander is now sleeping on the surface of its target comet, controllers are still keen to find just where it came to rest. For one thing it will help them better understand the region it briefly looked at after touching down on Wednesday.

The spacecraft disengaged from the Rosetta spacecraft and, after bouncing twice, came to rest in a yet-to-be discovered zone of Comet 67P/Churyumov-Gerasimenko. Ever since, officials at the European Space Agency and partner organizations have scoured Rosetta's and Philae's pictures for clues.

They are likely to be helped in their quest by an amazing new sequence of images released today that captured Philae as it flew across the frozen landscape of the comet.

It follows a breakthrough this weekend when enhanced Navcam images from Rosetta showed Philae near the surface just after its first touchdown. The lander, which only shows up as a couple of pixels in the image, is visible along with its shadow, showing that it is actually in the space equivalent of "mid-air" when the pictures was taken.

Then today, a composite image based on pictures from Rosetta's high-resolution OSIRIS camera showed Philae drifting across the comet eastward as it came in for a landing, touched down and then bounced up again. "The final location of Philae is still not known," ESA wrote in a blog post accompanying the image, but said that a combination of data from the Rosetta orbiter and Philae lander (particularly pictures) should soon help track down the location.

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A composite image from Rosetta's OSIRIS camera shows the Philae lander coming for a touchdown and drifting to a as-yet-unknown landing spot on Comet 67P/Churyumov–Gerasimenko. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The key is now to track where the bounces brought the lander. After two bounces, it came to rest (likely on its side) in a zone that only received 1.5 hours of sunlight daily, far less than what the mission called for. Philae had landing batteries that gave it a boost of energy for a few days, but the juice ran out on Friday and solar panels have not yet been able to obtain enough of a charge to keep going.

It is possible that the Rosetta spacecraft could spot the small lander, although the difficulty is that it would just be a few pixels on a complicated surface of light, shadow and dust. Earlier this week, controllers tried to use a landing experiment called COmet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT), which was there to learn about the comet's structure but was also being used to triangulate signals from the orbiting Rosetta spacecraft.

COmet Nucleus Sounding Experiment by Radiowave Transmission - See more at: http://sen.com/news/philae-keeps-on-working-as-rosetta-team-try-to-track-it-down#sthash.jdKRlTih.dpuf

Clues to Philae's landing site could also come from panoramas and other images that the lander sent to Earth during its brief activities on the surface. The lander is in hibernation, but could re-emerge from its nap to do more science from time to time. Perhaps more clues about its landing site could be found then.

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The first, unprocessed, panoramic image from the surface of a comet taken by Rosetta’s lander Philae. A sketch shows the lander’s position. Credit: ESA/Rosetta/Philae/CIVA

Philae performed the first (and second, and third) "soft landing" on a comet that humanity ever performed. The first object to hit a comet was an impactor lobbed by NASA's Deep Impact probe to Comet Tempel 1 in 2005. So far, the lander took pictures (a fraction of which have been released to the public) and did a surge of science on its surroundings.

Scientists had hoped that Philae would survive several months on the surface of the comet, but that depended on if it got to the surface and where it landed. The lander had no system to avoid obstacles on the comet. Additionally, harpoons that should have anchored it to the surface failed to fire for reasons controllers are still trying to figure out. Observers point out, however, that Philae and Rosetta have been flying for a decade in space without mechanical service, which could lead to some inevitable problems.

Comet 67P is still being examined closely by the orbiting Rosetta spacecraft, which will track its changes as it draws closer to the Sun in 2015. This will be the first time a single comet has been watched so closely as it approaches the inner Solar System.

By examining 67P's composition and chemical changes, astronomers are not only looking to improve comet predictions, but also to better understand our origins in the Solar System. The Sun, planets and other objects are thought to have coalesced from smaller objects billions of years ago, meaning that comets and asteroids are more pristine bodies from primative materials around when the Solar System was formed.