kolamaanu

Just as in the previous Rosetta/Philae AMA I hope you don't mind a lot of questions from one person at once. Only Philae questions in this one. Split up into different parts.

Legs:

1. Some reports have said two feet rests on the ground, some three. Are they all on the ground? If not, which of the feet are actually touching the surface?

2. The icescrews are passive systems, but is there any sensor that indicate how much they've moved?

3. Do you have timings of the touchdowns of the feet during the first touchdown? The OSIRIS images indicates, to a layman, that there were four distinct touches on the surface by the feet, having timings for which feet and when would help in visualizing how it came down and bounced back up.

4. What kind of articulation/active control does the legs have? When you raised Philae slightly how was it done?

Harpoons:

1. During the initial landing confusion, wouldn't the MUPUS sensors within the harpoons have indicated that they did not fire? Was it simply a matter of this data comming in later due to priorities on what to send from Philae/Rosetta to earth?

2. What kind of material is the harpoons supposed to be able to deal with? I've seen one mention that a compressive strength > 2 MPa might mean that the harpoons wouldn't anchor safely. But I've also read that the allowable range is 300 kPa - 5 MPa. (References: for 2 MPa value http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1392.pdf, for 5 MPa value http://www.esmats.eu/esmatspapers/pastpapers/pdfs/2003/thiel.pdf)

3. A follow up observation depending on the answer to the previous one. Could it be that the harpoons not firing was a blessing in disguise, considering the amount of velocity they might have imparted on Philae if they didn't anchor properly and instead rebounded.

4. Assuming contact is reestabilshed with Philae, is it worth attempting to fire the harpoons at some point? Either to get the MUPUS sensor values from them, i.e. material strength (mode 4!) and subsurface temperature, or to get a better hold for SD2 if that would prove necessary.

Solar panels:

1. You have given some general information on this already, but would you be willing to share specific times for when and how long the different panels are illuminated? I suppose the top panel is especially intresting as the top contains heat absorbers in addition to the solar panel.

2. Early reports said you had 1.5 hours of less than 1 watt and 20 minutes of 3-4 watts at the landing site. But in the Rosetta/Philae AMA you said the total illumination period was 4.5 hours. Is Philae itself in the shadows during that time and only some of the surrounding illuminated. Do you simply not get any power worth mentioning during the the unaccounted ~3 hours?

3. How much change in recieved power was the rotation of Philae expected to provide?

ÇIVA:

1. ÇIVA took three rounds of panoramas from my understanding: after first touchdown and twice at the final landing site. Is the first set so garbled that you can't even get anything useful out of it (not necessarily in the sense of pretty pictures for publishing)? The second has been shown. Was the third panorma a complete failure as well due to the light conditions?

2. What is the timestamps of the released ÇIVA images?

CONSERT:

1. The CONSERT experiment relies quite a bit on a good landing site to get full advantage of it. Posts indicate that you know its position to 100m, is the position suitable for CONSERT?

2. To build upon 5. When did CONSERT run? I was under the impression it would only be run when Rosetta was on the other side of the comet, but as you didn't know where Philae is...

3. As a layman looking at the ROLIS images it seems one of the CONSERT antennas might be resting on the ground, if so, would that be an issue for CONSERT?

ROLIS:

1. Are the unpublished images good in the sense of focus/exposure?

ROMAP:

1. How big of a boon were the bounces for this instrument? I don't know if you can quantify but...

General questions:

1. Would you be willing to speculate on how long until every Philae experiment can say whetever they got useful information from Philae? That is to say not clear results, but just that they have something to study to begin with. Thinking about an experiment like APXS, which might have gotten some result even though they had lens cap issue, if any dust got there. Or SESAME DIM, that I haven't heard anything about at all.

2. What was the rotational speed of Philae before and directly after the first touchdown?

3. Let's say you, through the power of magical foresight, would have known Philae would bounce as it did. What would you have attempted to do differently with its delivery to the comet (and/or had Philae do differently after first touchdown)?

4. 46p/Wirtanen was the originally target which the landing gear was designed for, a much smaller comet. How would you have liked to change the gear even before launch, i.e. without the knowledge you have about the surface today, that you couldn't do?

Hope Philae wakes up next year, without being too grumpy! Thanks for the AMA.

(As an aside, perhaps the ESA web team could put out a compiled version of this AMA on the Rosetta blog later?)

Hopefully you don't mind a whole lot of questions at once from one person. I've split them up into what I see as Rosetta respectivly Philae questions.

Rosetta questions:

1. How much fuel does Rosetta still have? The nominal mission end is in 2015, but will fuel be an issue if you get an extension into 2016?

2. Is there any chance of Rosetta surviving a second hibernation, following the comet out to aphelion and back for a second go at observing the comet? It would take it even further out from the sun than it was in the first hibernation, so I suppose the power available would be an even greater problem than before.

3. If you think 2. is a possiblity, would it even be worthwhile to attempt it? Would alternative ends be more rewarding (e.g. attempting to land Rosetta on the comet)?

4. If you attempt to (soft)land Rosetta on the comet, how exactly will the power situation work out, and how well could it even communicate with earth?

5. Has the enviornment around the comet posed any problems at all to the operations of Rosetta so far? If we ignore what must be quite a lumpy gravitiational field.

6. What has been the most unexpected/exciting thing that Rosetta has told you about the comet so far?

7. The scientific phase of Rosetta begins now, it is said. But surely all the instruments have gotten a chance to do their thing during the Philae landing site mapping/delivery phase too. I can understand how OSIRIS might have been forced to prioritize Philae quite a bit and that the specific orbits used might have had Philae in mind to ease mapping, but how does this new phase really differ from before?

8. Will Rosetta ever go for a specific close approach to attempt to pinpoint Philae, or will it only do so for purely scientific investigations?

9. Did any other Rosetta instrument attempt to image Philae when it was first released, such as say, VIRTIS? I'm a bit unsure of their capabilities in this respect, could they even have seen it when Philae was still relatively close? Would this just have been way too superfluous?

10. Building upon 9. Did any experiments have any "use" for Philae as an physical object with known properties.

11. Which experiments other than CONSERT has the most to gain from looking at the data provided by Philae, to better understand and improve upon their own results.

12. Do you know the reason behind the "hiccups" during the hibernation period (that is the reboot in 2012 and the need for a second bootup during its wakeup)?

13. Any new issues with Rosetta, is the flywheels doing okay?

Philae questions:

1. Both the harpoons and, correct me if I am wrong, the lander itself had accelerometers. The lander accelerometers were turned off during descent to prevent them from triggering the touchdown sequence, were they never turned on again? Were the accelerometers in the harpoons not on either?

2. Related to 1. During the initial landing confusion, wouldn't the MUPUS sensors within the harpoons have indicated that they did not fire? Was it simply a matter of this data comming in later due to priorities on what to send from Philae/Rosetta to earth?

3. The ice screws on the feet are passive system, but does that mean there isn't any sensor at all to even to see if they have moved?

4. The latest ESA Rosetta blog post seems to indicate that of the SESAME experiments both CASSE and PP worked. Does this mean you have an idea of which feet were on the ground at the final landing position now?

5. The CONSERT experiment relies quite a bit on a good landing site to get full advantage of it. Posts indicate that you know its position to 100m, is the position suitable for CONSERT?

6. To build upon 5. When did CONSERT run? I was under the impression it would only be run when Rosetta was on the other side of the comet, but as you didn't know where Philae is...

7. CIVA took three rounds of panoramas from my understanding: at first touchdown and twice at the final landing site. Is the first set so garbled that you can't even get anything useful out of it (not necessarily in the sense of pretty pictures for publishing)? The second has been shown. Was the third panorma a complete failure as well due to the light conditions?

8. The ROLIS images have not been released, but are they good in the sense of focus/exposure?

9. Is the ROMAP team very happy about the bounce? :)

10. Would you be willing to speculate on how long until every Philae experiment can say whetever they got useful information from Philae? That is to say not clear results, but just that they have something to study to begin with. Thinking about an experiment like APXS, which might have gotten some result even though they had lens cap issue, if any dust got there. Or SESAME DIM, that I haven't heard anything about at all.

11. Would you speculate on whetever a landing on 46P/Wirtanen would have lead to a very different result. The descent speed would have been quite a bit lower at least, so maybe the damping might have been more effective?

12. If you, through the power of magicical foresight, would have known Philae would bounce as it did, what would you have attempted to do differently with its delivery to the comet and/or had Philae do differently after first touchdown.

Thank you for an exciting mission and an exciting landing, hope you get the most out it with a phoenix rising up again next year with signals from the surface. Good luck with your future operations!

(As an aside, perhaps the ESA web team could put out a compiled version of this AMA on the Rosetta blog later?)

That is very suprising, I'm definitely one of those who thought that all spots could be done by the legs and a bit of drifting, given a leg diameter of 2,6 m, with one reound later for the fourth. At least with the given size of the OSIRIS insets (i.e. 17 m according to http://blogs.esa.int/rosetta/2014/11/17/osiris-spots-philae-drifting-across-the-comet/). Guess I was wrong.

Is there any chance you will do a second, close up, pass of the first touchdown to see what it looks like now?

Seeing as there is Rosetta people answering and not just those from Philae. Let's go ahead with some Rosetta questions.

1. How much fuel does Rosetta still have? The nominal mission end is in 2015, but will fuel be an issue if you get an extension into 2016?

2. Is there any chance of Rosetta surviving a second hibernation, following the comet out to aphelion and back for a second go at observing the comet? It would take it even further out from the sun than it was in the first hibernation, so I suppose the power available would be an even greater problem than before.

3. If you think 2. is a possiblity, would it even be worthwhile to attempt it? Would alternative ends be more rewarding (e.g. attempting to land Rosetta on the comet)?

4. If you attempt to (soft)land Rosetta on the comet, how exactly will the power situation work out, and how well could it even communicate with earth?

5. Has the enviornment around the comet posed any problems at all to the operations of Rosetta so far? If we ignore what must be quite a lumpy gravitiational field.

6. The scientific phase of Rosetta begins now, it is said. But surely all the instruments have gotten a chance to do their thing during the Philae landing site mapping/delivery phase too. I can understand how OSIRIS might have been forced to prioritize Philae quite a bit and that the specific orbits used might have had Philae in mind to ease mapping, but how does this new phase really differ from before?

7. Did any other Rosetta instrument attempt to image Philae when it was first released, such as say, VIRTIS? I'm a bit unsure of their capabilities in this respect, could they even have seen it when Philae was still relatively close? Would this just have been way too superfluous?

8. Building upon 7. Did any experiments have any "use" for Philae as an physical object with known properties.

9. Which experiments other than CONSERT has the most to gain from looking at the data provided by Philae, to better understand and improve upon their own results.

10. Do you know the reason behind the "hiccups" during the hibernation period (that is the reboot in 2012 and the need for a second bootup during its wakeup)?

11. Any new issues with Rosetta, is the flywheels doing okay?

Thanks again for the AMA!