Here’s something you don’t see very often or ever for that matter. We can see the shadow of ESA’s Rosetta spacecraft on Comet 67P/Churyumov-Gerasimenko.
During the close flybys of a couple week ago, only 6 km separated spacecraft and comet. During the flyby the sun was directly between sun and comet so a shadow of about 20 x 50 meters (66 x 164 feet) was projected onto the comet. ESA was able to capture the image with the OSIRIS camera.
The pair were about 2.35 AU from the Sun so if I did the math correctly the light levels would be approximately 5.5 times less bright than what we see around us.
Approximate brightness relative to us is about the distance in AU (astronomical units) to the power of 2,
2.35 AU 2 = 5.5 (in this case 5.5 X dimmer)
Is this a first? I can’t think of any example of shadows on other comet encounters.
ESA has a nice write up and more pictures at the Rosetta blog, check it out.
Rosetta’s Philae lander too this picture of its home, Perihelion Cliff, on comet 67P/Churyumov-Gerasimenko. Philae was released by Rosetta on 12 November 2014. The landing did not go quite as planned and the anchor harpoons did not fire. After the initial impact Philae did start sending back data, turns out the lander actually bounced twice. Philae is at the bottom of a cliff and is shaded so there is no power being generated by the solar panels. Click here to get a representation of the landing location.
Contact with the lander was lost when the batteries aboard Philae ran down. Philae may have no power there is hope in August 67P/Churyumov-Gerasimenko will be close enough to the sun for the solar panels on Philae to get enough light to return to life.
By close I mean really close! Rosetta will be a nail biting 6 km / 3.7 miles from Comet 67P/Churyumov–Gerasimenko. Good thing it’s ESA doing it is all I can say, if anybody can pull it off, they can. At times during the flyby Rosetta will almost speed match the rotational rate of the comet, an amazing opportunity for detail observations from many of Rosetta’s instruments.
“The upcoming close flyby will allow unique scientific observations, providing us with high-resolution measurements of the surface over a range of wavelengths and giving us the opportunity to sample – taste or sniff – the very innermost parts of the comet’s atmosphere,” says Matt Taylor, ESA’s Rosetta project scientist.
One of the instruments on board ESA’s Rosetta called COSIMA, short for the COmetary Secondary Ion Mass Analyser one of three dust analysis experiments.
Essentially this instrument has a plate for catching dust grains from the comet at fairly low speeds. The dust grains shown above is two of the grains collected and they have yielded some interesting results.
I’ll let ESA explain:
Two examples of dust grains collected by Rosetta’s COmetary Secondary Ion Mass Analyser (COSIMA) instrument in the period 25–31 October 2014. Both grains were collected at a distance of 10–20 km from the comet nucleus. Image (a) shows a dust particle (named by the COSIMA team as Eloi) that crumbled into a rubble pile when collected; (b) shows a dust particle that shattered (named Arvid).
For both grains, the image is shown twice under two different grazing illumination conditions: the top image is illuminated from the right, the bottom image from the left. The brightness is adjusted to emphasise the shadows, in order to determine the height of the dust grain. Eloi therefore reaches about 0.1 mm above the target plate; Arvid about 0.06 mm. The two small grains at the far right of image (b) are not part of the shattered cluster.
The fact that the grains broke apart so easily means their individual parts are not well glued together. If they contained ice they would not shatter; instead, the icy component would evaporate off the grain shortly after touching the collecting plate, leaving voids in what remained. By comparison, if a pure water-ice grain had struck the detector, then only a dark patch would have been seen.
These ‘fluffy’ grains are thought to originate from the dusty layer built up on the comet’s surface since its last close approach to the Sun, and will soon be lost into the coma.
Be sure to check the Rosetta Blog. The have this and results from six other Rosetta’s science instruments since arriving at Comet 67P/Churyumov-Gerasimenko – great stuff!!
ESA’s Rosetta spacecraft took this image of Comet 67P/Churyumov-Gerasimenko last November with the OSIRIS camera. By overexposing the comet the wisps of cometary dust is highlighted.
Rosetta has an instrument called MIDAS and its job is to capture 67P/C-G particles. About the time this image was taken MIDAS captured a particle measuring 10 micrometres, which is way larger than was expected.
“This is still the beginning of the activity compared to what we expect to see in summer this year,” says OSIRIS principal investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. “From the last perihelion passage we know that the comet will evolve by a factor of 100 in activity at that time compared to now.”
Rosetta continues to orbit around Comet 67P/Churyumov-Gerasimenko. This image is a mosaic taken on 03 January with Rosetta’s NAVCAM.
The view shows the newly named Imhotep region which is the smooth area and at least some of the rougher area above it. The name Imhotep is for the famous architect of Egyptian pyramids from the 27th century BC The name was released during the American Geophysical Union on 17 December 2014.
Check out the Rosetta Blog for the details and a larger version to really take advantage of the excellent detail.
It be could be the location of ESA’s Philae lander on comet 67P/Churyumov-Gerasimenko has been narrowed down. The image above is from that location and we are looking at what has been named “Perihelion Cliff.”
The image was taken with the CIVA camera (Comet Infrared and Visible Analyser) on Philae.
To see a graphic showing the position of the Philae in the context of topographic modeling click here. (image credit as above via JPL)
Rosetta will be doing a very close approach of the comet in February when it will come within 6.4 km / 4 miles of the surface. I’m not sure where that will occur related to the location of Philae.
Knowing the location of Philae is would be a big relief. I have not heard or seen specifically the location is known for certain, but we are closer to knowing than we were.
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.
I’ve not posted a Rosetta update in a little while. The spacecraft is still at 67P/Churyumov-Gerasimenko
This image is part of a four-frame mosaic and shows both lobes of the comet. Of particular interest is the 1 km wide depression on the left. It is thought this is the area where the little Philae lander ended up. High resolution imaging is being used to search for the lander – see “Homing in on Philae’s final landing site“.
This orientation also provides a good view onto the plateau that was previously considered as candidate landing site A – close to the ‘join’ between the two right-hand side images frames. The dark circular region is a large pit. The cliff walls that drop down onto this plateau seem to show slightly brighter sections, perhaps reflecting compositional differences, or fresher material that has yet to be degraded by exposure to the space environment.
The Philae lander might be hibernating and as far as I know the whereabouts of the lander isn’t known for sure, we do know about the journey.
The mosaic above is a series of images taken by the OSIRIS narrow angle camera aboard Rosetta over about a half hour. At the time Rosetta was only 15.5 km / 28 miles from the surface of the comet.
The mosaic captures Philae starting at the lower left and follows it upward as labeled on the image.
Like I said in the beginning, mission managers don’t know where Philae is but they will find it. It is known the lander was moving east with a rate of travel about a half a meter per second, that’s really slow for a spacecraft. Think about a leisurely walk, now go slower by better than half, on average, you would still probably beat Philae in a race.
Will Philae be found? I would say yes most likely it will. Data returned from the mission including the CONSERT ranging data, OSIRIS and navcam images on Rosetta along with Philae’s ROLIS and CIVA cameras should reveal the resting spot. When the lander is found mission managers will have a much better idea about the future of the mission.