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Headshot of Emily Lakdawalla


Posted by Emily Lakdawalla

12-11-2014 10:21 CST

Topics: Rosetta and Philae, pretty pictures, comets, mission status, comet Churyumov-Gerasimenko

The landing happened on time just after 16:02 UT today! Philae mission manager Stephan Ulamec said: "Philae is talking to us! The first thing he told us was the harpoons have been fired and rewound. We are sitting on the surface."

Well, this turned out not to be true. There followed a period of immense confusion about what actually happened upon landing, and it was not helped by the fact that The Planetary Society's website went down for a long period this afternoon. (When our website has major issues, sometimes it can be brought back online in a day-old form that, therefore, does not include the immensely popular posts that triggered the breakdown. While this prevents issues, it also prevents visitors from seeing popular, fresh posts, so it can be frustrating. But our host worked hard to recover us and we're back online in real time now.)

It's now very late in the evening after a long day so I'll suggest to readers that you go to my Twitter stream for the nitty gritty details of what unfolded this evening. But here are the high points:

  • Philae landed at 16:03 UT...maybe (see below)
  • Philae proceeded to return lots of science data.
  • The cold-gas thruster did not fire.
  • The harpoons did not fire, either.
  • The screws in the landing feet did their screwy thing.
  • But there are indications that the lander is not anchored securely to the surface.
  • In particular, according to the ROMAP magnetic instrument, Philae actually bounced, producing "3 landings at 15:33, 17:26 and 17:33 UTC." Note the 2-hour delay. That is a lot of time, meaning Philae could've moved a lot of distance between bounces.
  • Still, all the science instruments are returning data.
  • The most-anticipated data was from the ÇIVA panoramic imager. Although the imaging sequence executed, there was a problem with the data that was returned to Earth; it had black stripes or bars or was just black. It's unclear what went wrong, especially since ÇIVA worked great during descent. They may ask Philae to re-run the ÇIVA sequence while the rest of the science sequence is executing (they can apparently do this in parallel) in order to try to get this important image observation acquired and on the ground.
  • But all the rest of the instrument data looks good.

Beyond that, it's mostly speculation. The next press briefing is planned for 2pm local (central European) time tomorrow. I plan to return to ESOC in the late, late morning, after a good night's sleep.

But first, there are a few images to share. Although it's hard to top OSIRIS' image of the departing Philae for drama, it's also very cool to see the first couple of ROLIS descent camera images of the landing site.

ROLIS' first image of Churyumov-Gerasimenko

ESA / Rosetta / Philae / ROLIS / DLR

ROLIS' first image of Churyumov-Gerasimenko
The ROLIS descent imager on the Philae lander took no photos for more than 10 years until shortly before Philae landed on the comet on November 12, 2014. This photo was taken from an altitude of 3 kilometers, at 14:38 UT, and demonstrated that Philae was on target for its selected landing site, Agilkia. A strut for one of the lander legs crosses the screen at upper right.

 There were other ROLIS images that showed up on Twitter. Here, Daniel Machacek has figured out how they all relate to each other, so you can see the first landing site. But this is only the site of the first landing! If Philae really did bounce, and spent two hours before hitting the ground again, it could've wound up in a quite different location.

Locating the Philae landing site

ESA / Rosetta / Navcam / Philae / ROLIS / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA

Locating the Philae landing site
This series of images indicates the location of the first touchdown of the Philae lander on comet Churyumov-Gerasimenko. A NavCam image, on the left, provides global context. The next two images, from the OSIRIS science camera, give regional context. The final two images, from the ROLIS descent camera, localize the landing site. However, indications are that the spacecraft bounced, so the final landing site is likely in a different location.

There's more to say, of course, but I am just completely done for the day. I'll update with more tomorrow. In the meantime: Congratulations Philae! And Rosetta!

See other posts from November 2014


Or read more blog entries about: Rosetta and Philae, pretty pictures, comets, mission status, comet Churyumov-Gerasimenko


Superluminal: 11/12/2014 07:21 CST

As weak as the gravity is on a comet, the bounce could have been so gentle that Philae may have slowly rose only a few meters above the surface. Imagine a rubber ball bouncing in super slow motion. Maybe it didn't bounce too far from it original landing site.

Andy: 11/12/2014 07:24 CST

Thank you so much for your detailed analysis and reporting on location, Emily! What a fantastic experience the last 36 hours must have been.

ethanol: 11/12/2014 08:15 CST

Superluminal: Doug Ellison on twitter has done some rough calculations which suggest that the height, in 67p's gravity field, for a 2 hour bounce would be on the order of half a kilometer. He's careful to specify that this is an estimate, but it gives you an idea about what sort of bounce we are talking about. And either way, after two hours the real question is what Philae's lateral speed was during this time.

CosmosQuest: 11/12/2014 09:06 CST

Emily I sure hope that at some point we can begin to have an open discourse on your blog about what comets are really made of. I sure hope others here on your blog post are willing to consider that this and all comets for that matter are made of exactly what your eyes tell you they are made of......solid rock not icy conglomerate with a crusty surface. there is no water or ice in or on this comet nucleus. For just a moment please ignore the density estimates and let your eyes tell you what you are looking at.

eriknz: 11/13/2014 12:02 CST

Thanks very much Emily for all your great work to keep us updated! I just wonder why ESA did not publish those ROLIS pictures. And why do they wait so long for the next briefing? There are so many obvious questions unanswered.

thechrisroberts: 11/13/2014 02:21 CST

On the bounce, do the timestamps imply that the lander was floating the entire time? Does the two hour window certainly indicate two hours off the surface, or just two hours between landing with something perhaps causing it to go adrift somewhere inside the two hour window rather than at the start of the window?

Kalle: 11/13/2014 02:52 CST

looks like Phile is talking to us this morning, no word yet on orientation but it is sending pictures :)

leovuyk: 11/13/2014 02:54 CST

The fact that there are no photos from the surface of 67P CG is supporting that Philae is submerged in the dusty top layer. See: Potential Philae landing gravity and dust (avalanche) problem, by tilted (non perpendicular) gravity vector and the thick dusty/snowy surface of Comet 67P CG. Dust/snow layer seems to be 2-3 meter thick, because landslide A, is a clear avalanche of 100x11 meter estimated depth 2-3 meter.

kalle: 11/13/2014 03:52 CST

@leovyk the latest from esa is that their is photos that are being processed now. doesn't the bouncing contradict that theory?

kalle: 11/13/2014 03:58 CST

first picture :)

leovuyk: 11/13/2014 04:06 CST

The first picture tells me that we are indeed submerged (under ground) but without lots of dust as I expected.

leovuyk: 11/13/2014 04:22 CST

The next picture (opposite) could tell us how deep the pit is we are in. Did you see the cracking in the rock? there seem to be tectonic forces active.

thebigh: 11/13/2014 04:44 CST

Eh? The picture does not suggest that Philae is buried. To me it looks like it is sitting comfortably on the surface.

Jeff: 11/13/2014 03:21 CST

Great! Can't wait to see the full panorama so we can so the opposite side of the spacecraft. BTW, is that a harpoon I see imbedded in the rock?

leovuyk: 11/14/2014 05:08 CST

Had Philae between first and last touchdown unreliable readings or even black outs?

leovuyk: 11/14/2014 05:15 CST

Is the last touchdown position of Philae full in line with the original decending direction to the comet? or did it make billard ball bounce in an other direction?

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