Philae Found In Final Hour! Comet Probe Slumbers In Boulder’s Shadow

Rosetta’s lander Philae has been identified in OSIRIS narrow-angle camera images taken on 2 September 2016 from a distance of 2.7 km. The image scale is about 5 cm/pixel. Philae’s 1 m-wide body and two of its three legs can be seen extended from the body. The images also provide proof of Philae’s orientation. A 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. Main image and lander inset: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0
Philae’s 3-foot-wide (1 meter)  body and two of its three legs can be seen extended from the body. The images also provide proof of Philae’s orientation. A Rosetta Navigation Camera image is shown at top right for context, with the approximate location of Philae on the small lobe of Comet Churyumov-Gerasimenko marked. You can see how the lander is tucked under a boulder in the red box in the left side photo. Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

We found our comet lander! Tipped over on its side and looking forlorn but still intact, Philae was discovered wedged into a dark crack on Comet 67P/Churyumov–Gerasimenko this weekend, less than a month before the end of the Rosetta mission.

In this cropped, close up view, you can see two of Philae's landing legs and the solar-cell wrapped body of the probe (to the left of the legs). Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/ID
In this cropped, close up view, you can see two of Philae’s landing legs and the solar cell-lined body of the probe (to the left of the legs). The lander’s about the size of a washing machine. Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/ID

The images were taken on Sept. 2 by the OSIRIS narrow-angle camera as the orbiter came within 1.7 miles (2.7 km) of the surface and clearly show the main body of the lander, along with two of its three legs tipped almost directly on its side. Now we can see why it was so difficult to reestablish communication with the doomed probe following the landing on Nov. 12, 2014. Not only that, but Philae rests in the shadow of an enormous sunlight-blocking boulder. Without enough sunshine for the solar panels to make electricity, there wasn’t enough power to recharge the craft’s batteries.

In this close up view, parts and instruments are labeled. Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
In this close up view, parts and instruments are labeled. Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

“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,” says Cecilia Tubiana of the OSIRIS camera team, the first person to see the images when they were downlinked from Rosetta yesterday.

Philae was last seen when it first touched down at Agilkia, bounced and then flew for another two hours before ending up at a location later named Abydos, on the comet’s smaller lobe. Harpoons, designed to fire and anchor the craft to the comet’s surface, failed to fire, causing the probe to hit and bounce off the surface several times before setting down.

Amazing image taken by the Philae lander of one of its legs resting on the comet's surface after landing and before the craft lost power. Credit: ESA/Rosetta/Philae/CIVA
This photo was taken by the Philae lander of one of its legs resting on the comet’s surface after landing back in November 2014. Can you match anything in this image with the photos taken (above) of Philae by the Rosetta spacecraft? Credit: ESA/Rosetta/Philae/CIVA

After three days, Philae’s primary battery was exhausted and the lander went into hibernation, only to wake up again and communicate briefly with Rosetta in June and July 2015 as the comet came closer to the Sun and more power was available.

Until today, mission control only known its general location. While most candidates could be discarded from analysis of the imagery and other techniques, evidence continued to build towards one particular target, which is now confirmed in images taken incredibly close to the surface of the comet.

“This remarkable discovery comes at the end of a long, painstaking search,” says

An OSIRIS narrow-angle camera image taken on Sept. 2, 2016 from a distance of 1.7 miles (2.7 km) in which Philae was finally identified. The image has been processed to see Philae more clearly while maintaining the details of the comet’s surface. The lander is located at the far right of the image in the circle. Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
An OSIRIS narrow-angle camera image taken on Sept. 2, 2016 from a distance of 1.7 miles (2.7 km) in which Philae was finally identified. The image has been processed to see Philae more clearly while maintaining the details of the comet’s surface. The lander is arrowed and circled at far right. Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

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.”

Besides putting to rest questions of the lander’s whereabouts,  scientists now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context.”We know where that ground actually is!” says Matt Taylor, ESA’s Rosetta project scientist.

Pits Ma’at 1, 2 and 3 show differences in appearance that may reflect their history of activity. While pits 1 and 2 are active, no activity has been observed from pit 3. The young, active pits are very steep-sided; pits without any observed activity are shallower and seem to be filled with dust. Middle-aged pits tend to have boulders on their floors from mass-wasting of the sides. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Pits Ma’at 1, 2 and 3 show differences in appearance that may reflect their history of activity. While pits 1 and 2 are active with jets of material being shot out, no activity has been observed from pit 3. The Rosetta spacecraft plans to observe the pits up close before its mission ends at month’s end. 
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The discovery comes less than a month before Rosetta descends to the comet’s surface. On 30 September, the orbiter will be sent on a final one-way mission to investigate the comet from close up, including the open pits in the Ma’at region, where it’s hoped that that photos will help to reveal secrets of the body’s interior structure. A controlled impact is set for September 30 around 10:30 UT (5:30 a.m. Central Daylight).

More information about the search for Philae along with additional images will be released soon. For now, it just feels great that Philae’s been found!

* Source: ESA

8 Responses

  1. Troy

    Now that we know that a probe can survive multiple bumps at comet gravity, the next such mission should use that as the mission design. Imagine a probe that pops off from time to time, it would have a tetrahedral shape like the Mars pathfinder able to open up in any orientation. When it gets done with a site, or if the sunlight isn’t available (or better yet make it nuclear) just pop off using a spring mechanism and off to the next site.

    1. astrobob

      Not a bad idea, Troy. I wonder though if that would be considered too risky — the probe could get itself wedged on the first bump.

      1. Troy

        Do you suppose getting wedged is what stopped it from doing another bounce?
        I have to hand it to the guy who found it in that image. Reminds me of a magazine my parents get where an acorn is placed on some picture within the magazine. It is a devil to find, even though it isn’t obscured in any way.

      2. caralex

        Maybe retractable legs to shrink its overall size and reduce protruding appendages that can get wedged in cracks, and a mini rocket to propel it forward again, might work.

        1. astrobob

          Good ideas, Carol. I’m thinking maybe a sphere like a bouncing beach ball. It might still get stuck but it would be less likely than something with legs.

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