I know, it’s been a while. Rosetta is still orbiting Comet 67P/Churymov-Gerasineko and the spacecraft is doing well.
It has to be, the distance between Rosetta and the comet is 200 km / 124 miles and the pair
are moving at 30.91 km/s / 69,143 mph!
The comet is a little over 310,344,000 km / 192,839,000 miles. The pair should be closing
in on the orbit of Mars, which it will do at a fairly shallow angle.
As the pair gets closer the expected increase in activity in terms of streamers coming off the comet is occurring.
The Rosetta blog shows an enhanced version and a nice description including topographical features of the comet.
A Rosetta NAVCAM image of Comet 67P/Churyumov-Gerasimenko from 81.4 km / 50.6 miles. ESA did a nice job of processing the image in order to bring out some of the outflow. The outflow should become more evident over time and give 67P/G-C the classic comet look.
In the mean time Rosetta is intermittently sending radio signals to the Philae lander to establish contact. So far nothing has been heard from the little lander. Possibly the solar panels have not built up enough power in the systems to function or maybe it is just too cold. The lander remains in hibernation.
Philae needs an internal temperature above -45 C / -49 F and five watts of power to turn on – which is pretty impressive. The lander needs to be able to generate 19 watts in order to send signals to Rosetta.
ESA is choosing when to send signals to Philae so the alignment between it and Rosetta and presumably the sun to have the best chance for success. The first half of April will be the next best opportunity to contact.
If you click the image above you will see a version with some of the craters labeled.
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.