Starship Asterisk*

PHILAE STILL TALKING!
While the search for the final landing site is still on-going, the lander is racing against the clock to meet as many of the core science goals as possible before the primary battery is exhausted. Under the low illumination conditions at Philae’s location, it is unlikely that the secondary batteries will charge up enough to enable extended surface operations.

All of the science instruments were deployed, including the instruments that required mechanical movement, such as APXS, MUPUS, and the drill, SD2, which is designed to deliver samples to the PTOLEMY and COSAC instruments inside the lander. ...
Philae's planned mission is expected to come to an end when batteries are exhausted sometime on Saturday; future contacts are possible if the illumination conditions change as the comet orbits closer to the Sun, enabling solar power to flow again.

The Rosetta orbiter mission continues as planned, with an immense amount of science observations still to come.

FIRST HOUR OF LANDER COMMUNICATION

Update from Stephan Ulamec, Lander manager at DLR:

“We’ve got data – all the house-keeping data and data from COSAC – although we’ve no idea what’s in there yet. The drill (SD2) moved up and down, but again, we don’t yet know what we have.”

“We did the lift and turn; the landing gear lifted by about 4 cm, and we turned about 35 degrees.

“The carousel of Ptolemy was also turned and we are running Ptolemy for a concentrated 'sniff'.

Instrument reminder:

COSAC: The COmetary SAmpling and Composition experiment (detecting and identifying complex organic molecules)

PTOLEMY: an evolved gas analyser, which obtains accurate measurements of isotopic ratios of light elements, such as hydrogen, carbon, nitrogen and oxygen.

SD2: Sampling, drilling and distribution subsystem (drilling up to about 23 cm depth and delivering material to onboard instruments for analysis)

OUR LANDER’S ASLEEP
With its batteries depleted and not enough sunlight available to recharge, Philae has fallen into 'idle mode' for a potentially long silence. In this mode, all instruments and most systems on board are shut down.

"Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence," says DLR's Stephan Ulamec, Lander Manager, who was in the Main Control Room at ESOC tonight.

"This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered."
...
From now on, no contact would be possible unless sufficient sunlight falls on the solar panels to generate enough power to wake it up.

The possibility that this may happen was boosted this evening when mission controllers sent commands to rotate the lander's main body, to which the solar panels are fixed. This may have exposed more panel area to sunlight.
... However, given the low recharge current available from the solar cells, it is considered unlikely that contact with Philae will be established in the coming days.

The hugely successful Rosetta mission will continue, as the spacecraft tracks comet 67P/C-G on its journey to the Sun.

ESA news release: Pioneering Philae completes main mission before hibernation
Rosetta’s lander has completed its primary science mission after nearly 57 hours on Comet 67P/Churyumov–Gerasimenko.

After being out of communication visibility with the lander since 09:58 GMT / 10:58 CET on Friday, Rosetta regained contact with Philae at 22:19 GMT /23:19 CET last night. The signal was initially intermittent, but quickly stabilised and remained very good until 00:36 GMT / 01:36 CET this morning.

In that time, the lander returned all of its housekeeping data, as well as science data from the targeted instruments, including ROLIS, COSAC, Ptolemy, SD2 and CONSERT. This completed the measurements planned for the final block of experiments on the surface.

In addition, the lander’s body was lifted by about 4 cm and rotated about 35° in an attempt to receive more solar energy. But as the last science data fed back to Earth, Philae’s power rapidly depleted.

... Meanwhile, the Rosetta orbiter has been moving back into a 30 km orbit around the comet.

It will return to a 20 km orbit on 6 December and continue its mission to study the body in great detail as the comet becomes more active, en route to its closest encounter with the Sun on 13 August next year.

Over the coming months, Rosetta will start to fly in more distant ‘unbound’ orbits, while performing a series of daring flybys past the comet, some within just 8 km of its centre.

I now appreciate why there was so much confusion yesterday. When Philae initially touched down, that triggered the end of its descent sequence and the start of its first block of science activity. Its instruments dutifully performed their measurements and Philae relayed these back to the orbiter -- all while Philae was steadily climbing away from the comet at a speed of 38 centimeters per second. At the same time, the internal flywheel was slowly being braked, and that caused Philae to rotate, which was incredibly confusing to a team that thought the spacecraft was stationary on the comet surface.

MUPUS on Philae Experiment Summary
Penetrator deployed properly, temperature drop within the PEN may indicate they hit something on deployment
Other devices saw improved performance after deployment, possibly changed Philae's attitude
Hammering proceeded to cycle through 4 increasingly stronger power settings, with no indication of penetration. The surface seems to be >2MPa hard. They speculate the surface to be composed of a hard ground covered by a fluffy surface (possibly tiny mineral grains or organics)
Data obtained, just nothing from beneath the surface.

Continuing MUPUS on Philae Results
@Philae_MUPUS
Results (10) The depth sensor shows some up and down but no progress. The control loop increased to power setting 2
Results (11) depth sensor still shows no progress. Control loop goes to power setting 3. Still no progress!

Results (12) This means that the stuff is really hard! A very interesting finding, not visible from orbit!

Results (13) We have a secret power setting 4. Nicknamed "desperate mode". Beyond the design specs. We activated it
Results (14) Still no progress. The hammer gave up and failed after 7 minutes. Jerzy was right. We were desperate, activated, were punished
Results (15) Surface must be >2 MPa* hard! The comet remains surprising bizarre and uncooperative
Results (16). To put this into perspective: MUPUS performed beautifully inside the specifications. The comet failed to cooperate
Results (17) The loss of subsurface data is sad. The detection of this very hard crust is a great find the orbiter couldn't have done

MargaritaMc wrote:Thank you, Nit. So are you saying that this possibly equates to the (variable) hardness of ice?
This is a totally new area for me, so forgive me if I'm asking a daft question.

Click to play embedded YouTube video.

Rosetta Lander Philae - Mupus & Sesame First Science Sequence

Published on 12 Sep 2013
Two of Philae's scientific experiments are operated at the same time. After a simulated deployment from the Lander MUPUS Penetrator is operated in 'Hammering Mode' and SESAME CASSE is recording the strokes.

Nitpicker wrote:I've just read as much about the MUPUS hammer and penetrator as I can find (not much), and I am no closer to figuring out what "> 2 MPa hard" means, or how to compare it to any known materials. The instrument is unlike any standard hardness, strength, or toughness test I know of in the field of mechanical engineering. In truth, whatever they were trying to measure in MPa (i.e. pressure, or force/area) was beyond the capability of the instrument anyway. But the test seems more like a standard penetration test used in geotechnical engineering, which typically tests soil density via one kind of empirical formula or another. Yet this test isn't normally measured in MPa, as far as I know. So, it remains a mystery to me.

MargaritaMc wrote:The test itself was simply aimed at getting some subsurface material. They weren't able to do this because the surface turned out to be much harder than had been anticipated. The designers of course made the machine over ten years ago. From what I've been reading the questions then included wondering if comets actually were solid bodies at all. And famously they've been described as "dirty snowballs". :D

Nitpicker wrote:I've just read as much about the MUPUS hammer and penetrator as I can find (not much), and I am no closer to figuring out what "> 2 MPa hard" means, or how to compare it to any known materials. The instrument is unlike any standard hardness, strength, or toughness test I know of in the field of mechanical engineering. In truth, whatever they were trying to measure in MPa (i.e. pressure, or force/area) was beyond the capability of the instrument anyway. But the test seems more like a standard penetration test used in geotechnical engineering, which typically tests soil density via one kind of empirical formula or another. Yet this test isn't normally measured in MPa, as far as I know. So, it remains a mystery to me.

UK Space Agency News Release: Philae finds hard ice and organic molecules

18 November, 2014

After a triple landing, positioning it in a new, unplanned location, conditions were not optimal, but Philae was able to work for more than 60 hours sniffing the atmosphere, drilling and hammering to send the resulting data back to Earth.

Icy Hardness

The team responsible for the MUPUS (Multi-Purpose Sensors for Surface and Sub-Surface Science) instrument, which hammered a probe into the comet, estimates that Comet 67P is hard as ice:

"Although the power of the hammer was gradually increased, we were not able to go deep into the surface,"

explains Tilman Spohn from the DLR Institute of Planetary Research, who is leading the research team. Shortly after the triple landing, the scientists could only hope that Philae would be in a position that would allow the probe to be hammered into the surface. However, with MUPUS it has been possible to directly study the strength of a comet’s surface for the first time – and 67P/Churyumov-Gerasimenko proved to be a ‘tough nut to crack’.

"We have acquired a wealth of data, which we must now analyse,"

says comet researcher Spohn. Only the thermal sensors and accelerometers in the anchors that should have fixed Philae to the comet’s surface were not used, because they were not deployed during the touchdown.

Listening to the comet

The team of the SESAME experiment (Surface Electrical, Seismic and Acoustic Monitoring Experiment) can confirm that Churyumov-Gerasimenko is not nearly as soft and fluffy as it was believed to be.

"The strength of the ice found under a layer of dust on the first landing site is surprisingly high,"

says Klaus Seidensticker from the DLR Institute of Planetary Research. The instrument CASSE, which sits in the feet of the lander, was turned on during the descent and clearly registered the first landing as Philae came into contact with the comet. From additional data, the mechanical properties of 67P will be derived. SESAME’s two other instruments suggest that cometary activity at this landing site is low, as well as revealing the presence of a large amount of water ice under the lander.

Images and radio waves before hibernation

One of the big ‘winners’ of the Philae landing is Stefano Mottola from the DLR Institute of Planetary Research, who is responsible for the ROLIS (ROsetta Lander Imaging System) camera. The instrument, mounted on the bottom of the lander, acquired images during the first descent showing the planned landing site, Agilkia. Even after the third landing, it proved possible to reactivate ROLIS and acquire images of the comet’s surface at close range. Thus, the team has data for two different locations on the comet.

A wealth of data was also obtained with the CONSERT (COmet Nucleus Sounding Experiment by Radio wave Transmission) instrument. To achieve this, the lander and orbiter were on different sides of the comet and worked together to analyse the comet nucleus by passing radio signals through it and creating a three-dimensional profile of the core. During the CONSERT measurements, Philae went into hibernation after the power from its primary battery was exhausted. This battery was flown through space already charged to ensure the completion of the first scientific work phase.

Sniffing for organic molecules

The last of the 10 instruments on board the Philae lander to be activated was the Sampling, Drilling and Distribution (SD2) subsystem, which was designed to provide soil samples for the COSAC and PTOLEMY instruments. It is certain that the drill was activated, as were all the steps to transport the sample to the appropriate oven. COSAC also worked as planned and was able to ‘sniff’ the atmosphere and detect the first organic molecules after landing. Now scientists need to analyse whether a soil sample was actually examined in the gas chromatograph. This will be done in collaboration with several instrument teams.
...

...One advantage of the shadier landing site in a crater is that the Philae lander will not overheat as quickly as the comet approaches the Sun, but will benefit from the stronger sunlight. The team managed to rotate the lander during the night of 14/15 November 2014, so that the largest solar panel is now aligned towards the Sun.

alter-ego wrote: I'm starting to think the fact the hammer broke, the MPa units are referring to tensile strength. If that's true than I've found that the low end of sandstone is 3 to 5 MPa.

As Claudia mentions, the fact the hammer broke means the surface hardness was significantly underestimated.

MargaritaMc wrote:That's useful information, thank you. In terms of pressure, a (geologist) friend I was chatting to told me that if a mountain bike ran over your foot it would be 0.24 megapascals. And a stiletto high heel it would be 3.24 megapascals.

MargaritaMc wrote: ...
alter-ego, where is the quote from Claudia that you mention? Is it one of the two Claudias on the Rosetta project? I haven't seen it on the blog.
...

Chris Peterson wrote: ...
Frankly, "hardness" is a sloppy term, and I'm surprised they're using it. Geologists generally use concepts based on more fundamental material strength properties, such as compressive and tensile stress, various types of strain and strength, elasticity, and other such values that are rigorously defined and which have values that do not depend on the nature of the tool used to measure them.

UK Space Agency News Release: Philae finds hard ice and organic molecules
...
Icy Hardness

The team responsible for the MUPUS (Multi-Purpose Sensors for Surface and Sub-Surface Science) instrument, which hammered a probe into the comet, estimates that Comet 67P is hard as ice:

alter-ego wrote:

MargaritaMc wrote: ...
alter-ego, where is the quote from Claudia that you mention? Is it one of the two Claudias on the Rosetta project? I haven't seen it on the blog.
...

I'm referring to the team member, Claudia Alexander.
I must admit I'm not twitter savvy so I may be totally misinterpreting the link preceding the tweet. I read the tweet below as being from Claudia (not to Claudia). Because she's is on the team, and that the link takes one to her account, that made sense. Please correct me if I'm wrong.

https://storify.com/brenthugh/philae-s- ... ts-results

Tweet.JPG

Before going into hibernation at 01:36 CET on 15 November 2014, the Philae lander was able to conduct some work using power supplied by its primary battery. With its 10 instruments, the mini laboratory sniffed the atmosphere, drilled, hammered and studied Comet 67P/ Churyumov-Gerasimenko while over 500 million kilometres from Earth. After a triple landing, positioning it in a new, unplanned location, conditions were not optimal, but Philae was able to work for more than 60 hours and send the resulting data back to Earth. It was controlled and monitored from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Lander Control Center (LCC). Now, the complicated data analysis begins. DLR's Scientific Director for the project, Ekkehard Kührt, is very pleased with the results so far. "We have collected a great deal of valuable data, which could only have been acquired through direct contact with the comet. Together with the measurements performed by the Rosetta orbiter, we are well on our way to achieving a greater understanding of comets. Their surface properties appear to be quite different than was previously thought.
...