Philae landing on the nucleus of Comet 67P C-G Options

[ZLD]

So I started working on an animation of the Philae landing images and something is really strange. Going by the capture times posted in the official animation and on the individual images, and using those times for the durations of each sequence tweening, it seemed to speed up and slow down.

So I started figuring up the velocities in each image and they are all over the place. From what I've read, the thruster on board never fired right?

Below is a list of the velocities figured between each image

1 - 15:32:59 @ 67.4m
---- 0.95m/s
2 - 15:33:09 @ 57.9m
---- 0.90m/s
3 - 15:33:19 @ 48.5m
---- 1.10m/s
4 - 15:33:28 @ 38.6m
---- 0.97m/s
5 - 15:33:38 @ 28.9m
---- 1.10m/s
6 - 15:33:48 @ 18.8m
---- 0.98m/s
7 - 15:33:58 @ 9.0m

What exactly is going on here? Its apparent in the animation I'm working on that something is not quite right.

[scalbers]

Do we now have the CIVA image times available? This might help with navigating the panorama.

[ZLD]

Looks like they are posted for the descent images but not for the panorama, at least on the link posted by 4throck.

[fredk]

So I started working on an animation of the Philae landing images and something is really strange... What exactly is going on here?

Nothing strange. The times are quoted to the second, not tenth or hundredth of a second. That means we must consider them as central values with uncertainties (or rounding errors) of +/- 0.5 second or even larger (if there are significant timing errors). There also should be uncertainties on the distances. Incorporate those uncertainties into the velocity calculations (ie, work out the corresponding velocity uncertainties) and they should all be consistent.

[SteveM]

Nothing strange. The times are quoted to the second, not tenth or hundredth of a second.

The times may only have been quoted to a second but can't we presume that Philae took images at constant intervals of (59 ±0.5)/6 seconds ≈ 9.8 ± 0.1 sec. Probably there's a more precise value in the spacecraft docs.

[flug]

I don't remember having seing bounce marks so clearly. From Dr Chris Tibbs tweet: https://twitter.com/chris_tibbs/status/611077375187677184

Look at the supplement to the recent Science article on the Philae landing(s). They made a 'subtracted' image by using an image just prior to touchdown and another just after touchdown. This looks a lot like that image. See figures S13, S14, and S15 from the supplement.

Links, a little more discussion & excerpts from the Supplement here--the supplement includes a lot of info about Philae post-impact.

Attached thumbnail(s)

 

[flug]

So I started working on an animation of the Philae landing images and something is really strange. Going by the capture times posted in the official animation and on the individual images, and using those times for the durations of each sequence tweening, it seemed to speed up and slow down. . . .

What exactly is going on here? Its apparent in the animation I'm working on that something is not quite right.

I assume you are going by the 'range' listed on each photo, and the time listed, in order to determine the velocity?

One issue is, what do they mean by 'range' and how was it calculated? Is it distance from the landing site, distance above the terrain, or something else? How was it determined and calculated?

Until we know the answers to those questions, we're really just guessing. But if (for example) it is distance above the terrain (as calculated using a terrain model of 67P, probably) that could explain the variations--it's going over some surface irregularities, which affect the range distance.

As I'm sure you know, over the time period under consideration--about 1 minute--to a first approximation Philae's velocity will be constant at somewhere just over 1 m/s. To a second approximation, it will be very, very slightly increasing at a constant rate, due to the Comet's gravity. (There are 3rd & 4th & 5th approximations that the physics folks can argue about, but for the purpose of making an animation over a one minute period, you probably only need the 1st approximation.)

Also, have a look at the Supplement to the recently released Science article about Philae's landing(s). The Supplement has some data about various photos taken before/after the first impact, that might be helpful for you.

[DoF]

They have the CIVA 7 image at http://www.dlr.de/dlr/en/desktopdefault.as.../#gallery/21184 now, which I don't recall seeing before. The CIVA 6 image they have is also rotated 90 degrees clockwise compared to what was released after the landing.

Emily Lakdwalla also tweeted that Philae has been found (https://twitter.com/elakdawalla/status/664550877408174080), so I'm assuming http://www.dlr.de/dlr/en/desktopdefault.as.../#gallery/19679 is the location that they have in mind then, although that's just speculation from my part.

[fredk]

Both 6 and 7 had been previously released, but these versions are the cleanest I've seen.

Here's the anaglyph:

And cross-eyed:

[DoF]

Right you are, I missed that. I see now that they were released during a Rosetta blog post all the way back in July, I had simply overlooked the anaglyph they had that time. Still a bit curious as to why they aren't the full 1024x1024.

[Decepticon]

I was just wondering if all the Philae surface images have been released?

[Herobrine]

I was just wondering if all the Philae surface images have been released?

The Escort Phase 1 block of science data was due in to ESA, from all instrument teams, by the 10th of September (65 days ago). ESA has said in the past that they try to get the data into the PSA about a week after they receive them. So far, only Escort Phase 1 data from MIDAS and RPC-ICA (and NAVCAM) have shown up in the PSA. I don't know if ESA is doing something with the other data before publishing it, or if all of the other instruments teams haven't delivered their data to ESA, two months after it was due, but I continue to expect we'll see it any day now. I'm not sure if some version of all of its images have been released yet, but either way, we won't have to work with 8-bit jpegs anymore soon enough.

[flug]

Emily Lakdwalla also tweeted that Philae has been found (https://twitter.com/elakdawalla/status/664550877408174080), so I'm assuming http://www.dlr.de/dlr/en/desktopdefault.as.../#gallery/19679 is the location that they have in mind then, although that's just speculation from my part.

I can't find anything more online about that recent announcement, but I too would guess the announcement is that that previously suspected location has been confirmed. This article published in Universe Today in June 2015 has some more information about the suspected location and some before/after images of it.

[Daba]

Philae has been found!

http://www.esa.int/Our_Activities/Space_Sc...ta/Philae_found

[dvandorn]

Well, it is very clear that this is indeed Philae. We can now compare some of its surroundings as they now appear to what they looked like in the CIVA pan. It looks like a lot of nice details show up here in that underlying sheet-like surface, that showed up in such great detail in the CIVA pan, at any rate. There may be some good ability to compare/contrast and look for changes.

One thing -- from the obvious orientation of the two visible legs, it looks like there should be a leg pointing almost directly at the observer's position. I don't see any signs of it, and yet I thought all three legs were seen in the CIVA pan. The one I can't see here would be the one that looked like it was pointing out at the sky, with no surface around it.

Do y'all think it's just that the one leg is hard to see because we're looking right down its length end-on? Or am I mistaken about the CIVA pan, and maybe Philae lost one of her legs in her final sequence of collisions?

-the other Doug