Category Archives: Rosetta

Comet Storm

If you were cruising along next to a comet and looked out your window you might see this scene. Reminds me of driving in a snowstorm except more random. This particular comet storm was outside of Rosetta during its journey with comet 67P/Churyumov–Gerasimenko.

ESA’s caption: Perhaps you live in a part of the world where you regularly experience snow storms or even dust storms. But for many of us, the weather forms a natural part of everyday conversation – more so when it is somewhat extreme, like a sudden blizzard that renders transport useless or makes you feel highly disoriented as you struggle to fix your sights on recognisable landmarks.

ESA’s Rosetta mission had a similar experience, for more than two years, as it flew alongside Comet 67P/Churyumov–Gerasimenko between 2014 and 2016. It endured the endless impacts of dust grains launched by gaseous outpourings as the comet’s surface ices were warmed by the heat of the Sun, evaporating into space and dragging the dust along.

This image was taken two years ago, on 21 January 2016, when Rosetta was flying 79 km from the comet. At this time Rosetta was moving closer following perihelion in the previous August, when the comet was nearer to the Sun and as such at its most active, meaning that Rosetta had to operate from a greater distance for safety.

As can be seen from the image, the comet environment was still extremely chaotic with dust even five months later. The streaks reveal the dust grains as they passed in front of Rosetta’s camera, captured in the 146 second exposure.

Excessive dust in Rosetta’s field of view presented a continual risk for navigation: the craft’s startrackers used a star pattern recognition function to know its orientation with respect to the Sun and Earth. On some occasions flying much closer to the comet, and therefore through denser regions of outflowing gas and dust, the startrackers locked on to dust grains instead of stars, creating pointing errors and in some cases putting the spacecraft in a temporary safe mode.

Despite its dangers, the dust was of high scientific interest: three of Rosetta’s instruments studied tens of thousands of grains between them, collectively analysing their composition, their mass, momentum and velocity, and profiling their 3D structure. Studying the smallest and the most pristine grains ejected is helping scientists to understand the building blocks of comets.

Two years before the image was taken, 20 January 2014, Rosetta was only just waking up from 31 months of deep-space hibernation. It arrived at its destination after 10 years in space  in August 2014, and released the lander Philae three months later. Rosetta made unique scientific observations of the comet until reaching its grand finale on 30 September 2016 by descending to the comet’s surface. By the end of the mission, more than a hundred thousand images had been taken by the high-resolution OSIRIS camera (including the one shown here) and the navigation camera, the majority of which are available to browse in the Archive Image Browser.

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

A Big Surprise from Rosetta


ESA – 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.

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.

Rosetta’s Legacy

Rosetta was an epic mission no doubt about it. For some looking at all the data from the mission is the best part; something akin to looking through a treasure chest, you never know what you might find.

Video

Moving a Boulder on a Comet

Take a look at these images of a boulder that moved on Comet 67P/Churyumov-Gerasimenko as seen by the Rosetta spacecraft.  Fascinating stuff.  The boulder clearly moved.  But how?

Here’s ESA’s caption (via NASA):
A 100 foot-wide (30 meter), 28-million-pound (12.8-million-kilogram) boulder, was found to have moved 460 feet (140 meters) on comet 67P/Churyumov-Gerasimenko in the lead up to perihelion in August 2015, when the comet’s activity was at its highest. In both images, an arrow points to the boulder; in the right-hand image, the dotted circle outlines the original location of the boulder for reference.

The movement could have been triggered in one of two ways: either the material on which it was sitting eroded away, allowing it to roll downslope, or a sufficiently forceful outburst could have directly lifted it to the new location. Indeed, several outburst events were detected close to the original position of the boulder during perihelion.

The images were taken by Rosetta’s OSIRIS camera on May 2, 2015 (left) and Feb. 7, 2016 (right), with resolutions of 7.5 feet (2.3 meters) per pixel and 2.6 feet (0.8 meters) per pixel, respectively.

Rosetta is a European Space Agency mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the U.S. participation in the Rosetta mission for NASA’s Science Mission Directorate in Washington.

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So first I’m siding with the erosion idea by way of off gassing or jets. It seems that a jet strong enough to directly lift a “12.8 million-kg” boulder would lift more material than just the boulder and if it did the boulder would likely show more of an impact mark as the soil looks sand-like. True the same forces could erase those marks but you’d think there would be some physical sign of such a powerful event. Still there are no “boulder-tracks” and again off-gassing might erase the tracks.

The other thing that isn’t explained is this: Is the 12.8 million-kg / 28 million-lb boulder a true 67P weight or is that what it would weigh here on Earth?  OR is this a measure of mass but not stated as such? This is a case where knowing the mass would be helpful. Like I said – fascinating stuff!

Image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Rosetta Archive

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The last of the NAVCAM images are now archived. The images in the latest  archive release are from the Rosetta’s last month of activity during the fantastic mission around Comet 67P/Churyumov-Gerasimenko.

This and other images can be found with the ESA Archive Image Browser

ESA’s description of the image above, one of the last five from Rosetta’s NAVCAM taken on 30 September 2016:

Single frame enhanced NavCam image taken on 29 September 2016 at 23:25 GMT, when Rosetta was 19.4 km from the centre of the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale at the surface is about 1.7 m/pixel and the image measures about 1.7 km across.

Image (and description): ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Rosetta Last Images

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One of the last images from Rosetta prior to touching down on comet 67P/Churyumov-Gerasimenko. The view above is from about 16 km / 10 mi and was obtained with the OSIRIS narrow-angle camera.

The image scale is about 30 cm / 12 in per pixel with a 614 m / 2,000 ft wide field of view!

Credits: ESA/Rosetta/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA via NASA

And this my friends is the very last image from Rosetta:

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WOW! AT just 20 meters or 66 feet Rosetta took this. According to ESA: “The image scale is about 5 mm/pixel and the image measures about 2.4 m across.” The image was taken with the OSIRIS wide-angle camera.

Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Rosetta Coverage

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NASA Television and the agency’s website will air the conclusion of ESA’s (European Space Agency’s) Rosetta mission from 6:15 to 8 a.m. EDT Friday, Sept. 30, with NASA commentary, interviews and analysis of the successful mission. The Rosetta mission will end with the controlled decent of the spacecraft onto the surface of comet 67P/Churyumov-Gerasimenko at around 7:20 a.m.

There will be a link here for the live feed of the end of this epic mission.

Credits: ESA/ATG medialab