Unexpected surprise: a final picture from Rosetta

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Scientists analysing a final telemetry sent by Rosetta immediately before it close down on a aspect of a comet final year have reconstructed one final picture of a touchdown site.

After some-more than 12 years in space, and dual years following Comet 67P/Churyumov–Gerasimenko as they orbited a Sun, Rosetta’s ancestral goal resolved on 30 Sep with a booster forward onto a comet in a segment hosting several ancient pits.

Reconstructed final picture from Rosetta

It returned a resources of minute images and systematic information on a comet’s gas, dirt and plasma as it drew closer to a surface.

But there was one final warn in store for a camera team, who managed to refurbish a final telemetry packets into a pointy image.

Rosetta’s final images in context

“The final finish picture transmitted from Rosetta was a final one that we saw nearing behind on Earth in one block moments before a touchdown during Sais,” says Holger Sierks, principal questioner for a OSIRIS camera during a Max Planck Institute for Solar System Research in Göttingen, Germany.

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

During operations, images were separate into telemetry packets aboard Rosetta before they were transmitted to Earth. In a box of a final images taken before touchdown, a picture data, analogous to 23 048 bytes per image, were separate into 6 packets.

For a really final picture a delivery was interrupted after 3 full packets were received, with 12 228 bytes perceived in total, or only over half of a finish image. This was not recognized as an picture by a involuntary estimate software, though a engineers in Göttingen could make clarity of these information fragments to refurbish a image.

Rosetta’s alighting site to scale

Owing to a onboard application software, a information were not sent pixel-by-pixel though rather layer-by-layer, that gives an augmenting turn of fact with any layer.The 53% of transmitted information therefore represents an picture with an effective application ratio of 1:38 compared to a expected application ratio of 1:20, definition some of a finer fact was lost.

That is, it gets a lot blurrier as we wizz in compared with a full-quality image. This can be likened to compressing an picture to send around email, contra an uncompressed chronicle that we would imitation out and hang on your wall.

The camera was not designed to be used next a few hundred metres from a aspect though a crook picture could be achieved regulating a camera in a special configuration: while a camera was designed to be operated with a colour filter in a visual beam, this was private for a final images. This would have resulted in a images being confused for a normal imaging unfolding above 300 m, though they came into concentration during a ‘sweet spot’ of 15 m distance.

Comet from 331 m

Approaching 15 m therefore softened a concentration and so turn of detail, as can be seen in a reconstructed picture taken from an altitude of 17.9–21.0 m and analogous to a 1 x 1 m block segment on a surface.

In a meantime, a altitude of a formerly published final picture has been revised to 23.3–26.2 m. The doubt arises from a accurate process of altitude calculation and a comet figure indication used.

The method of images gradually reveals some-more and some-more fact of a boulder-strewn surface, providing a durability sense of Rosetta’s touchdown site.

Source: ESA




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