Tag: Philae

Less than a month before Rosetta’s mission ends the spacecraft’s high resolution camera has finally located Philae in its final resting spot on the surface of Comet 67P/C-G.

The images were taken on 2 September by the OSIRIS narrow-angle camera as the orbiter came within 2.7 km of the surface and clearly show the main body of the lander, along with two of its three legs. The images also provide proof of Philae’s orientation, making it clear why establishing communications was so difficult following its landing on 12 November 2014.

The image on the right clearly shows the lander on its side with one leg sticking up, as theorized by the Rosetta engineers based on the small amount of data they had received before Philae went dead. Furthermore, the wide image at the link above shows that the lander landed exactly as predicted by data, up against a wall — in this case a large boulder — which placed it in shadow most of the time.

Link here. No big news. The lander remains silent, and has not yet been precisely located on the surface, though they have a pretty good idea where it is. They expect to get images of it on the surface sometime before September, when Rosetta’s mission will end with its own attempted touchdown on Comet 67P/C-G.

After another attempt to contact Rosetta’s lander Philae ended with no response, engineers now consider the spacecraft dead

“We did not hear anything,” says lander manager Stephan Ulamec. In the best-case scenario, Philae may have received the command and moved, but be unable to respond due to a damaged transmitter. It is more likely that the signal was not received. The team will try a few more commands, but it looks like Philae has officially gone. “We have to face reality, and chances get less and less every day as we are getting farther and farther away from the sun,” says Ulamec. “At some point we have to accept we will not get signals from Philae anymore.”

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The scientists and engineers operating Rosetta have begun planning the mission’s spectacular finale, when they will spend several months orbiting within six miles of Comet 67P/C-G’s surface before very gently crashing the spacecraft on the surface.

Because of many factors, Rosetta is not expected to survive the impact, no matter how gently it lands. However, the data it will send back in its final months as it makes tighter and tighter orbits should be well worthwhile.

In related news, the science team has released an animation, posted below the fold, of their re-creation of the flight and crash landing of Philae on the comet.
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The magic of engineering: Using the seven images Philae snapped as it made its descent to Comet 67P/C-G, engineers have created a short movie simulating what the surface would have looked like as the lander descended.

I have posted the video below the fold. Be sure to go to the link above however to find out how this was done.
» Read more

Link here.

The story is fascinating because the lander’s behavior and response to commands has been quite puzzling. They have had about a half dozen short contacts of varying length, all interspersed with a lot of intermittencies. At the moment they have not entirely given up on Philae, since based on what they know of its location and condition it could remain functional through the end of this year. They also recognize that re-establishing contact is becoming increasingly unlikely. The big hope is that once the comet moves farther away from the sun and becomes less active, they will be able to move Rosetta in closer, when the chances of contact will improve.

The Rosetta science team today released all data obtained by the mission through Philae’s landing on November 14.

If you go here you can browse all the images the spacecraft’s high resolution camera took during that time period. You might even discover something the project scientists missed in their first perusal.

Cool image time! The Philae science team yesterday published in Science a set of papers describing their results from the lander’s approach and bouncing landing on Comet 67P/C-G.

Data were obtained during the lander’s seven-hour descent to its first touchdown at the Agilkia landing site, which then triggered the start of a sequence of predefined experiments. But shortly after touchdown, it became apparent that Philae had rebounded and so a number of measurements were carried out as the lander took flight for an additional two hours some 100 m above the comet, before finally landing at Abydos.

Some 80% of the first science sequence was completed in the 64 hours following separation before Philae fell into hibernation, with the unexpected bonus that data were ultimately collected at more than one location, allowing comparisons between the touchdown sites.

The images from lander so far released show the approach to the first site, with one boulder getting larger and larger as it descends, followed by images at the final landing site, showing a fractured, uneven, and very rough surface with the lander apparently sitting sideways with one foot off the ground.

An animation of the first touchdown, created by these images, can be viewed here.

Update: A good summary of the results can be read here.

Engineers on the Rosetta team are struggling to figure out why they cannot get a solid communications lock with their Philae lander, and have come up with several explanations.

One possible explanation being discussed at DLR’s Lander Control Center is that the position of Philae may have shifted slightly, perhaps by changing its orientation with respect to the surface in its current location. The lander is likely situated on uneven terrain, and even a slight change in its position – perhaps triggered by gas emission from the comet – could mean that its antenna position has also now changed with respect to its surroundings. This could have a knock-on effect as to the best position Rosetta needs to be in to establish a connection with the lander.

Another separate issue under analysis is that one of the two transmission units of the lander appears not to be working properly, in addition to the fact that one of the two receiving units is damaged. Philae is programmed to switch periodically back and forth between these two transmission units, and after tests on the ground reference model, the team has sent a command to the lander to make it work with just one transmitter. As Philae is able to receive and accept commands of this kind in the “blind”, it should execute it as soon as it is supplied with solar energy during the comet’s day.

They have heard from Philae since July 9. Because of comet activity they have had to pull Rosetta back away from the nucleus to protect it, and are now focusing its primary activity on observations, not communications with Philae. They will continue to try to bring Philae back to full functioning life, but the priority is now the comet.

On July 9 Philae successfully transmitted data to Rosetta for the first time in more than two weeks.

Although the connection failed repeatedly after that, it remained completely stable for those 12 minutes. “This sign of life from Philae proves to us that at least one of the lander’s communication units remains operational and receives our commands,” said Koen Geurts, a member of the lander control team at DLR Cologne.

The mood had been mixed over the last few days; Philae had not communicated with the team in the DLR Lander Control Center (LCC) since 24 June 2015. After an initial test command to turn on the power to CONSERT on 5 July 2015, the lander did not respond. Philae’s team began to wonder if the lander had survived on Comet 67P/Churyumov-Gerasimenko.

The intermittent nature of Philae’s attempts at communication are puzzling. Normally, they either would have communications or they would not. For good communications to break off like this repeatedly is puzzling. It is almost as if there is a loose wire causing communications to go on and off, which seems an unlikely explanation for this problem.

This update describes the status of the effort by the Rosetta science team to re-establish a stable communications channel with the Philae lander on the surface of Comet 67P/C-G.

Confirmed contacts between Rosetta and Philae have been made on 13, 14, 19, 20, 21, 23, and 24 June, but were intermittent during those contact periods. For example, the contact on 19 June was stable but split into two short periods of two minutes each. Conversely, the contact on 24 June started at 17:20 UT (on board Rosetta) and ran for 20 minutes, but the quality of the link was very patchy and only about 80 packets of telemetry were received. Prior to this, on Tuesday, 23 June, there was a 20-second contact, but no stable link was established and consequently no telemetry data were received.

There are many reasons why the contacts have been so intermittent, much of it related to Philae’s position on the surface. To improve things, they are carefully adjusting Rosetta’s position relative to the comet while avoiding placing the spacecraft in a position where the coma’s dust will cause problems.

Engineers have begun shifting Rosetta’s trajectory paralleling Comet 67P/C-G in order to maximize communications with the lander Philae.

Commands to adjust the trajectory were successfully uploaded Monday evening; further commands will be uplinked on Thursday evening. The spacecraft will perform two manoeuvres, one on Wednesday morning and the second on Saturday morning. The effect of the two ‘dog-leg’ burns will be to bring the orbiter to a distance of 180 km from the comet and to reproduce the orbiter-comet geometry of the first contact.

We should therefore not expect further news from Philae for the rest of this week.

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.

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.

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.

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.

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.