With a second short contact on Sunday engineers have confirmed that Philae is healthy and capable of doing science. Now they must re-arrange Rosetta’s orbit and re-establish regular communications to get that science started.
After more than six months of silence after its bouncing landing on Comet 67P/C-G, Rosetta’s Philae comet lander has awakened and resumed communications with the science team.
More details here. The data they have so far received, which is still being analyzed, suggests that the lander has awakened previously and gathered data at that time. More to come!
Cool image time! The Rosetta science team has spent much effort trying to locate Philae, which attempted to land on Comet 67P/C-G in November. The image on the right shows what they think is their best candidate, the bright feature in the center. It was not there prior to Philae’s landing attempt.
Because there are many uncertainties, however, this might not be Philae.
Ultimately, a definitive identification of this or any other candidate as being Philae will require higher-resolution imaging, in turn meaning closer flybys. This may not be possible in the near-term, as issues encountered in navigating close to the comet mean that the opportunity to make flybys at significantly less than 20 km from the surface may be on hold until later in the mission. But after the comet’s activity has subsided, Rosetta should be able to safely operate in close proximity to the comet nucleus again.
The other possibility of further refining Philae’s location would come if the lander were to receive enough power to wake-up from its hibernation and resume its scientific study of 67P/C-G. Then, CONSERT could be used to perform additional ranging measurements and significantly reduce the uncertainties on the lander’s location. At the moment, Philae is still in hibernation, but the mission team remain hopeful that, as the comet moves closer to the Sun along its orbit, the lander will receive enough power in the coming weeks or months to wake up and transmit a signal to Rosetta.
Rather than simply turn off the spacecraft when its funding runs out at the end of 2015, Rosetta’s science team have proposed that the mission get a nine month extension, during which they will slowly spiral into the comet and gently land.
Their proposal is similar to what American scientists did with their NEAR spacecraft, which hadn’t been designed to land on an asteroid but was successfully eased onto the surface of Eros, where it operated for a very short time.
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.
Data collected by both Rosetta and Philae has confirmed that Comet 67P/C-G does not have a significant magnetic field.
The data review also found that Philae touched the surface four times, not three, during its unintended bouncing descent.
Because of the problems Rosetta experienced during its last close fly-by of Comet 67P/C-G the engineering team has worked out a new approach strategy for future observations.
Essentially, they are postponing any close fly-bys for the near future. Instead, they will observe from farther away, while reassessing the situation and planing for later opportunities.
Meanwhile, on April 12 the next opportunity to listen for Philae begins.
Want to help the Rosetta science team study Comet 67P/C-G? If you are an amateur astronomer, you can!
They are asking amateurs with larger telescopes to observe the comet as it makes its close approach to the Sun and report their observations. The science team will compare their observations with the amateurs. This will teach us how to interpret future comet events when seen from afar.
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 has made the first detection of molecular nitrogen in the coma of Comet 67P/C-G.
The in situ detection of molecular nitrogen has long been sought at a comet. Nitrogen had only previously been detected bound up in other compounds, including hydrogen cyanide and ammonia, for example. Its detection is particularly important since molecular nitrogen is thought to have been the most common type of nitrogen available when the Solar System was forming. In the colder outer regions, it likely provided the main source of nitrogen that was incorporated into the gas planets. It also dominates the dense atmosphere of Saturn’s moon, Titan, and is present in the atmospheres and surface ices on Pluto and Neptune’s moon Triton.
It is in these cold outer reaches of our Solar System in which the family of comets that includes Rosetta’s comet is believed to have formed.
After eight days of sending signals, listening for Philae, and getting no response, Rosetta has ceased its effort.
“It was a very early attempt; we will repeat this process until we receive a response from Philae,” says DLR Project Manager Stephan Ulamec. “We have to be patient.” On 20 March 2015 at 05:00 CET, the communication unit on the Rosetta orbiter was switched off. Now, the DLR team is calculating when the next favourable alignment between the orbiter and the lander will occur, and will then listen again for a signal from Philae. The next chance to receive a signal from the lander is expected to occur during the first half of April.
They always knew that it was unlikely for the lander to come alive this soon, but they tried anyway. The odds improve, however, in the coming months.
Rosetta has snapped a new image of Comet 67P/C-G’s smaller lobe that not only shows the increased activity around the nucleus but captures areas of the comet that had formally been in darkness. The image also includes the region where engineers think Philae landed, which I think is the area just below the brightest flat area in the center of the lobe. That this area is now in daylight is why engineers are hopeful that Philae might soon wake up.
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.
Beginning on Thursday Rosetta engineers will start searching for a signal from their lander Philae, hidden somewhere on the surface of Comet 67P/C-G.
The likelihood of getting an answer this soon is not high, but the lander is now getting about twice as much sunlight as it did when it landed in November. There is a chance it will warm up enough and get enough stored power to come to life.
Cool image time! During Rosetta’s February 14 close fly-by of Comet 67P/C-G the spacecraft’s high resolution camera captured an image showing the spacecraft’s shadow on the surface of the comet nucleus.
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.
Astronomers have identified a nearby star, now 20 light years away, that 70,000 years ago flew past the solar system at a distance of only 0.8 light years.
The star’s trajectory suggests that 70,000 years ago it passed roughly 52,000 astronomical units away (or about 0.8 light years, which equals 8 trillion kilometers, or 5 trillion miles). This is astronomically close; our closest neighbor star Proxima Centauri is 4.2 light years distant. In fact, the astronomers explain in the paper that they are 98% certain that it went through what is known as the “outer Oort Cloud” – a region at the edge of the solar system filled with trillions of comets a mile or more across that are thought to give rise to long-period comets orbiting the Sun after their orbits are perturbed.
I feel it necessary to note that the Oort Cloud itself has never been directly observed and only exists theoretically based on the random arrival of comets from the outer solar system.
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.
The Rosetta team has provided a detailed update describing their so far unsuccessful search for Philae on the surface of Comet 67P/C-G.
In addition, the update also looks into the possibility that Philae might wake up in the late spring when the comet’s orbit and rotation changes enough so its solar panels are more exposed to the Sun.
Bottom line: Don’t expect them to find the lander from images. Right now it is a mere three pixels in size. And whether it will come back to life as well also remains unknown.
Link here.
The first surprising result emerging from VIRTIS’s study of Comet 67P/Churyumov-Gerasimenko is the measurement of its albedo, or how much sunlight is reflected by the surface of the nucleus. With an albedo of only 6%, about half as much as the Moon’s, 67P/C-G is one of the darkest objects in the Solar System. Such a low reflecting power indicates that the surface of the comet contains minerals such as, for example, iron sulfides, but also carbon-based compounds. The low albedo also indicates that there is little or no water ice on the outermost layers of the surface of the nucleus.
“This clearly doesn’t mean that the comet is not rich in water, but only that there is no water ice in the outermost shell, just over one millimetre thick,” explains Fabrizio Capaccioni, VIRTIS Principal Investigator from INAF-IAPS in Rome, Italy. “The reason for this is rooted in the recent history of the comet’s evolution, since repeated passes in the vicinity of the Sun cause surface ice to sublimate.”
This result, combined with other Rosetta data, also suggests that during each pass the dust that did not escape along the comet’s tail settled back down to coat the surface and hide the lower layers of water ice.
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.
Climate change: Data from Rosetta has shown that the coma surrounding Comet 67P/C-G’s nucleus varies far more than had been expected by Earth-based observations.
“From a telescope, images of a comet’s atmosphere suggest that the coma is uniform and does not vary over short periods of hours or days. That’s what we were expecting as we approached the comet,” said Dr. Stephen Fuselier, a director in the SwRI Space Science and Engineering Division and the lead U.S. co-investigator for the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis Double Focusing Mass Spectrometer (ROSINA DFMS) instrument. “It was certainly a surprise when we saw time variations from 200 km away. More surprising was that the composition of the coma was also varying by very large amounts. We’re taught that comets are made mostly of water ice. For this comet, the coma sometimes contains much more carbon dioxide than water vapor.”
The variations might be seasonal, or even reflect a variation from day to night.
Expect more news stories about Comet 67P/C-G from Rosetta. The journal Science is today publishing a special section on results from Rosetta.
The science team running Rosetta has released an image (cropped by me on the right) from the probe’s high resolution camera showing the fine structure of Comet 67P/C-G’s plumes.
I call them plumes rather than jets, which is the word the scientists use as well as everyone else, because it appears to me that they really aren’t jets, tightly confined flows of material coming from a nozzle-like opening. Instead, the image makes me think of very fast-rising plumes of smoke rising from an extinguished fire.
This image was taken in November, and is one of only a very tiny handful of images released from the high resolution camera. Rosetta’s science team has been very possessive of images from this camera, holding them back for their own research papers to follow in the future. Even here, the image is not very detailed. I wonder what cool stuff this camera has snapped close in that they have not yet shown us.
The uncertainty of science: Fused droplets found in many places across the globe and theorized to have come from a comet major impact that caused a major climate change around 13,000 years ago have now been found to have instead come from common house fires.
Since the 1970s when the Walter Alvarez found evidence of an asteroid impact in the Yucatan that could have caused the dinosaur extinction 65 million years ago, planetary scientists have seen asteroid or comet impacts everywhere. After all, impacts are cool disasters that play well to television producers and funding agencies.
Read this story however. It describes some very solid scientific work that wipes out one one of those cool theories, replacing it with something quite mundane.
Comet Lovejoy has brightened faster and more quickly than expected, and has now become just visible to the naked eye.
The webpage gives good instructions for finding it, visible each evening now below the constellation of Orion.
The Rosetta team has released a gif movie of Comet 67P/C-G, created by compiling images taken over a period of two weeks in late November.
The movie shows the nucleus’s rotation during that period, which helps viewers understand better its geography.
