Tag: comets

Time for many cool images! The Rosetta science team has just released to the public another batch of images from its navigational camera.

The 1776 images cover the period between 23 September and 21 November 2014, corresponding to Rosetta’s close study of the comet down to distances of just 10 km from the comet centre – 8 km from the surface – and the images taken during and immediately following the landing of Philae on the comet.

You can browse through them at your leisure, making your own discoveries if you have a sharp eye and know something about planetary geology.

The science team for Rosetta’s navigation camera have released to the public 1297 images taken of Comet 67P/C-G as the spacecraft began its approach on August 1, 2014 through September 23, 2014.

The release also included a video assembled from these images, showing the comet nucleus as Rosetta approached from August 1 to August 22. I have embedded that video below. As you watch, you will think, “How does this thing stay together?” Though the video shows the nucleus’ rotation at a highly accelerated rate, which exaggerates the stresses on the object, the question is a good one, and in fact, is actually predicting the future. Eventually, this nucleus will break up.

During its most recent close fly-by of Comet 67P/C-G Rosetta had a number of issues that caused the spacecraft to go into safe mode.

During the most recent flyby, a number of issues were reported, starting with the primary star tracker encountering difficulties in locking on to stars on the way in towards closest approach. Attempts were made to regain tracking capabilities, but there was too much background noise due to activity close to the comet nucleus: hundreds of ‘false stars’ [from comet debris] were registered and it took almost 24 hours before tracking was properly re-established.

In the meantime, a spacecraft attitude error had built up, resulting in the high gain antenna off-pointing from the Earth. Indeed, a significant drop in the radio signal received by ground stations on Earth was registered. Following recovery of the star tracker system, the off-pointing was immediately automatically corrected and the operations team subsequently saw a return to a full strength signal from the spacecraft.

However, issues with false stars were still occurring. Cross comparisons with other navigation mechanisms showed inconsistencies with the star trackers and some on board reconfigurations occurred. While attempting to reconfigure those, the same error occurred again leading this time to an automatic safe mode on Sunday afternoon. Safe modes occur when certain spacecraft parameters fall out of their normal operating ranges and the spacecraft automatically takes measures to preserve its safety. This also includes switching off the science instruments to protect them.

Rosetta is operating nominally now, but these issues are going to get more serious in the coming months, as the comet gets more active. Rosetta’s engineering team is going to have to come up with a method for the spacecraft’s star trackers to distinguish between stars and the debris in the comet’s coma. If they don’t it is likely that they will have to reduce the close fly-bys significantly.

Rosetta’s high resolution camera has taken a color image of Comet 67P/C-G’s narrow neck, the area where the most plume activity has taken place.

When seen with the human eye, comet 67P/Churyumov-Gerasimenko is grey – all over. With its color filters Rosetta’s scientific imaging system OSIRIS, however, can discern tiny differences in reflectivity. To this effect, scientists from the OSIRIS team image the same region on the comet’s surface using different color filters. If, for example, the region appears especially bright in one of these images, it reflects light of this wavelength especially well.

“Even though the color variations on 67P’s surface are minute, they can give us important clues”, says OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. In a recent analysis performed by the OSIRIS team, the Hapi region clearly stands out from the rest of the comet: while most parts of 67P display a slightly reddish reflectivity spectrum as is common for cometary nuclei and other primitive bodies, the reflection of red light is somewhat lower in this region.

They as yet do not know exactly why the smooth area at the neck has a very slight blueish tinge, though they suspect it is because of the presence of a higher percentage of frozen water.

More cool images! Rosetta’s navigation camera has taken another very amazing close-up of Comet 67P/C-G, snapped during the February 14 fly-by.

The cropped section above focuses on the transition between two regions, the generally smooth area called Imhotep on the right and the more mountainous and rugged area called Khepry on the left. Go to the link for the full image, which also includes an interesting description of the engineering problems of doing these close fly-bys.

Link here.

The images are only from the spacecraft’s navigational camera, and while cool, are thus to me not that interesting. What the high resolution camera saw they are once again keeping under wraps, for release later as part of a paper by the scientists involved.

Cool image time! In preparation for a close fly-by of Comet 67P/C-G on Saturday — where it will zip past the comet less than three miles above its surface — Rosetta has eased away to a distance of about 60 miles, allowing its navigation camera to snap its first single frame image since the spacecraft’s initial close approach last summer.

The image brightness has been adjusted to make the plume more obvious. Also, if you look closely at the full resolution version of the image, it is possible to see the dusty material that forms the coma surrounding the nucleus.

Cool image time! A new navigation camera mosaic from Rosetta shows both a clear plume rising out of Comet 67P/C-G as well as a “large number of small white blobs and streaks in the image are likely specks of dust or other small objects in the vicinity of the comet.”

The fact that, unlike previously, they did not have to significantly overexpose the image to bring out the plume and dust illustrates the increasing activity at the comet.

Data from a U.S. instrument on Rosetta has shown that the water venting off of Comet 67P has increased significantly since the spacecraft arrived.

“In observations over a period of three months [June through August, 2014], the amount of water in vapor form that the comet was dumping into space grew about tenfold,” said Sam Gulkis, principal investigator of the MIRO instrument at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of a paper appearing in the special issue [of Science].

The amount of water at the maximum level averages about 40 ounces every second.

In related Rosetta news today, data from the comet is showing that the dust leaving its surface is dust that had settled back down after the comet’s last close pass to the Sun.

Link here. These images are from Rosetta’s high resolution camera OSIRIS, the results from which have been kept very closely secret by the Rosetta science team. Today however they published a bunch of papers in the journal Science, so we are finally beginning to see some of their amazing images.

Take a look. Each one illustrates how alien a place Comet 67/C-G is.

More info on these papers can be found here and here.

Even more here, from the Rosetta team.