Unexpected surprise: A final image from Rosetta

September 28, 2017, European Space Agency
A final image from Rosetta, shortly before it made a controlled impact onto Comet 67P/Churyumov–Gerasimenko on 30 September 2016, was reconstructed from residual telemetry. The image has a scale of 2 mm/pixel and measures about 1 m across. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Scientists analysing the final telemetry sent by Rosetta immediately before it shut down on the surface of the comet last year have reconstructed one last image of its touchdown site.

After more than 12 years in space, and two years following Comet 67P/Churyumov–Gerasimenko as they orbited the Sun, Rosetta's historic mission concluded on 30 September with the spacecraft descending onto the comet in a region hosting several ancient pits.

It returned a wealth of detailed images and scientific data on the comet's gas, dust and plasma as it drew closer to the surface.

But there was one last surprise in store for the camera team, who managed to reconstruct the final telemetry packets into a sharp image.

"The last complete image transmitted from Rosetta was the final one that we saw arriving back on Earth in one piece moments before the touchdown at Sais," says Holger Sierks, principal investigator for the OSIRIS camera at the Max Planck Institute for Solar System Research in Göttingen, Germany.

"Later, we found a few telemetry packets on our server and thought, wow, that could be another image."

During operations, images were split into telemetry packets aboard Rosetta before they were transmitted to Earth. In the case of the last images taken before touchdown, the image data, corresponding to 23 048 bytes per image, were split into six packets.

Annotated image indicating the approximate locations of some of Rosetta’s final images. Note that due to differences in timing and viewing geometry between consecutive images in this graphic, the illumination and shadows vary. Top left: a global view of Comet 67P/Churyumov–Gerasimenko shows the area in which Rosetta touched down in the Ma’at region on the smaller of the two comet lobes. This image  was taken by the OSIRIS narrow-angle camera on 5 August 2014 from a distance of 123 km. Top right: an image taken by the OSIRIS narrow-angle camera from an altitude of 5.7 km, during Rosetta’s descent on 30 September 2016. The image scale is about 11 cm/pixel and the image measures about 225 m across. The final touchdown point, named Sais, is seen in the bottom right of the image and is located within a shallow, ancient pit. Exposed, dust-free terrain is seen in the pit walls and cliff edges. Note the image is rotated 180º with respect to the global context image at top right. Middle: an OSIRIS wide-angle camera image taken from an altitude of about 331 m during Rosetta’s descent. The image scale is about 33 mm/pixel and the image measures about 55 m across. The image shows a mix of coarse and fine-grained material. Bottom right: the penultimate image, which was the last complete image taken and returned by Rosetta during its descent, from an altitude of 24.7±1.5 m. Bottom left: the final image, reconstructed after Rosetta’s landing, was taken at an altitude of 19.5±1.5 m. The image has a scale of 2 mm/pixel and measures about 1 m across. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

For the very last image the transmission was interrupted after three full packets were received, with 12 228 bytes received in total, or just over half of a complete image. This was not recognised as an image by the automatic processing software, but the engineers in Göttingen could make sense of these data fragments to reconstruct the image.

Owing to the onboard compression software, the data were not sent pixel-by-pixel but rather layer-by-layer, which gives an increasing level of detail with each layer.

The 53% of transmitted data therefore represents an image with an effective compression ratio of 1:38 compared to the anticipated compression ratio of 1:20, meaning some of the finer detail was lost.

That is, it gets a lot blurrier as you zoom in compared with a full-quality image. This can be likened to compressing an image to send via email, versus an uncompressed version that you would print out and hang on your wall.

The camera was not designed to be used below a few hundred metres from the surface but a sharper image could be achieved using the camera in a special configuration: while the camera was designed to be operated with a colour filter in the optical beam, this was removed for the last images. This would have resulted in the images being blurred for the normal imaging scenario above 300 m, but they came into focus at a 'sweet spot' of 15 m distance.

Approaching 15 m therefore improved the focus and thus level of detail, as can be seen in the reconstructed image taken from an altitude of 17.9–21.0 m and corresponding to a 1 x 1 m square region on the surface.

In the meantime, the altitude of the previously published last image has been revised to 23.3–26.2 m. The uncertainty arises from the exact method of altitude calculation and the comet shape model used.

The sequence of images progressively reveals more and more detail of the boulder-strewn surface, providing a lasting impression of Rosetta's touchdown site.

Explore further: Image: Rosetta's ever-changing view of a comet

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14 comments

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britton_beckham
1 / 5 (2) Oct 02, 2017
wow, the comet service is so.... icy. You guys see it too, right?
jonesdave
2 / 5 (4) Oct 03, 2017
wow, the comet service is so.... icy. You guys see it too, right?


Which part of the fact that the ice is below the dust, and/or intimately mixed with it, are you not understanding?
Might I suggest going to Google Scholar, and inputting the following: Rosetta; 67P; ice. I think you'll find there have been plenty of detections of ice. Not to mention a shed load ejected from the impact at Tempel 1. Or use your web browser to look at this pretty image of Hartley 2:
https://smd-prod....trip.jpg

I suspect you've been reading the scientifically illiterate loon Thornhill a bit too much.
cantdrive85
1 / 5 (2) Oct 03, 2017
It's just "dark" ice, just out of view so as to not falsify an entire branch of pseudoscience that jonesdumb clings to so desperately. By the way jonesdumb, the amounts of ice detected on the surface are miniscule and not in the amounts one would expect for an ice cube.
jonesdave
2 / 5 (4) Oct 04, 2017
It's just "dark" ice, just out of view so as to not falsify an entire branch of pseudoscience that jonesdumb clings to so desperately. By the way jonesdumb, the amounts of ice detected on the surface are miniscule and not in the amounts one would expect for an ice cube.


Hey, dummy. What came out of Tempel 1 when it was impacted?
https://www.aanda...ght.html
https://pdfs.sema...12a3.pdf

What do you think that this is a picture of?
https://smd-prod....trip.jpg

Is it ice, or is it a total disaster for the interplanetary arm of the Medellin cartel?

jonesdave
2 / 5 (4) Oct 04, 2017
What is the density of a comet, EU idiots?
Where is the H2O & various other gases coming from?
Why does ice come out of a comet when you smack it with an impactor?
Why was there a shed load floating around Hartley 2?
Why does the idiot Thornhill have such a grip on your feeble minds? When he is quite obviously scientifically illiterate?

All questions that we will never get an answer to.
jonesdave
2 / 5 (4) Oct 04, 2017
By the way jonesdumb, the amounts of ice detected on the surface are miniscule and not in the amounts one would expect for an ice cube.


Why would it be lying around on the surface, you loon? You do know at what temperature water ice sublimes in a vacuum, right? Deary me.
cantdrive85
1 / 5 (2) Oct 04, 2017
Why would it be lying around on the surface, you loon? You do know at what temperature water ice sublimes in a vacuum, right? Deary me

http://www.scienc...0017.jpg
jonesdave
2.6 / 5 (5) Oct 04, 2017
Why would it be lying around on the surface, you loon? You do know at what temperature water ice sublimes in a vacuum, right? Deary me

http://www.scienc...0017.jpg


Ancient stuff.

Answer the following:
What is the density of a comet, EU idiots?
Where is the H2O & various other gases coming from?
Why does ice come out of a comet when you smack it with an impactor?
Why was there a shed load floating around Hartley 2?
Why does the idiot Thornhill have such a grip on your feeble minds? When he is quite obviously scientifically illiterate?

cantdrive85
1 / 5 (2) Oct 04, 2017
jonesdumb thinks the guy who developed the theory he idolizes is a loon and would prefer to gloss over any historical perspective of such.

Oh yeah, I forgot. "Where's the electrolyte in plasmas?" LOL!
jonesdave
2.6 / 5 (5) Oct 04, 2017
jonesdumb thinks the guy who developed the theory he idolizes is a loon and would prefer to gloss over any historical perspective of such.

Oh yeah, I forgot. "Where's the electrolyte in plasmas?" LOL!


And you are still stuck on a model from over 60 years ago, before we had observational evidence that comets were covered by more dust than Whipple envisaged. They are still composed of ice and dust. For which there is plenty of evidence.

What is the density of a comet, EU idiots?
Where is the H2O & various other gases coming from?
Why does ice come out of a comet when you smack it with an impactor?
Why was there a shed load floating around Hartley 2?
Why does the idiot Thornhill have such a grip on your feeble minds? When he is quite obviously scientifically illiterate?
cantdrive85
1 / 5 (3) Oct 04, 2017
And you are still stuck on a model from over 60 years ago,

It is you who is still stuck on a model from over 60 years ago, developed prior to the space-age. You're lying again jonedumb.
cantdrive85
1 / 5 (2) Oct 04, 2017
Here is Philea making snow angels on 67P.
http://www.smh.co...hi8.html
jonesdave
2 / 5 (4) Oct 04, 2017
And you are still stuck on a model from over 60 years ago,

It is you who is still stuck on a model from over 60 years ago, developed prior to the space-age. You're lying again jonedumb.


Nope, I accept the findings that we've had since the Halley missions in 1986. Comets are composed of ice and dust. We have seen that ice and dust. I'm really not sure what you are on about. How about spelling it out, because you don't seem to have a point to your posts.
jonesdave
1 / 5 (3) Oct 04, 2017
Nope, I accept the findings that we've had since the Halley missions in 1986. Comets are composed of ice and dust. We have seen that ice and dust. I'm really not sure what you are on about. How about spelling it out, because you don't seem to have a point to your posts.


Well, it seems like cantthink has gone mute. Maybe he would like to explain the following:

What is the density of a comet, EU idiots?
Where is the H2O & various other gases coming from?
Why does ice come out of a comet when you smack it with an impactor?
Why was there a shed load floating around Hartley 2?
Why does the idiot Thornhill have such a grip on your feeble minds? When he is quite obviously scientifically illiterate?

Come on, woo boy, let's hear it. What do you think a comet is? What is your proof (lol).
Just another semi-educated moron who has been taken in by the loons T & T. Yes? Give it up son. This stuff is way beyond you. Isn't it?

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