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Philae update: My last day in Darmstadt, possibly Philae's last day of operations

Posted by Emily Lakdawalla

14-11-2014 12:33 CST

Topics: Rosetta and Philae, mission status

The press room was nearly empty this morning -- only a few stalwarts are left. I, Eric Hand (from Science), and Steven Young (Astronomy Now) were hanging around to follow what could be Philae's very last day of work on the comet before falling silent, and Chris Lintott and Alok Jha were wandering around getting last bits of video for BBC.

Because Philae is in such a shadowed position, it is not receiving enough sunlight to recharge its batteries, so has only the battery power it left Rosetta with. That power will definitely take it through today, hopefully through tonight, and possibly but not likely into the next day, but no further.

So, since we're coming to the end of things, they've started taking more risks. They've completed all the science they can do without moving any of the mechanical devices on the lander, getting about 80% of the data they would have expected from the first science sequence. Last night, almost immediately after I posted my last update, they made the decision to command the lander to deploy the MUPUS soil penetrator. The first uplink attempt failed, but a second attempt got the sequence through, and around midnight European time the instrument was on and at work. Philae fans around the world were able to follow all of these events in detail through the active MUPUS Twitter account.

This device can measure the temperature of the subsurface, how fast heat is flowing out of the comet, and how rapidly the comet's uppermost surface conducts heat. The MUPUS team shared this video of a test, showing how the self-hammering probe operates. (Caution: audio levels are high.)

The next morning, ESA confirmed the successful deployment of MUPUS and made the decision to perform the riskiest remaining operation: to try to drill into the comet and retrieve samples for the lander's gas analyzers, which will try to measure directly the chemical and isotopic composition of the comet. The drill had protruded 25 centimeters from the lander before Rosetta set below Philae's confined horizon. We will have no further contact with Philae until after 9:00 p.m. local time. Did the drill go to completion? Did it deliver a sample to COSAC? We don't know.

It's possible we'll never find out. Philae is very, very close to draining its battery. During a Google+ Hangout today, Valerie Lommatsch, an engineer at the Lander Control Center at DLR in Germany (and also, incidentally, the first woman scientist or engineer I've seen on a panel at this event), gave a detailed explanation of the lander's power situation. Here are my notes on her remarks (which are as close to verbatim as I could take them, but which are still my impression of her remarks):

CNES battery team has been doing simulations continuously to find out how long batteries will last; last night we calculated we needed 80 watt-hours to complete the SD2 and COSAC block. [SD2 is the drill, COSAC the science instrument to which the drill is delivering a sample.] We thought we might have 100 watt-hours left, if primary battery temperature stays up. One thing that is unfortunate is that the one command line that didn't reach the lander was one that would've put it into a low power mode which uses about 2 watts less energy than standby mode. And that is the mode that we have to be in as we wait for link to come up. It's going to be really, really close whether we make it to the link or not.

We're thinking about two ideas right now during the next block with the landing gear. One is we might rotate panel 1. We think there is shadow cast on panel 2, so rotating a larger panel [into the sun] could result in same situation as now. One other possibility is running the landing gear up without any controls, just running up and then hoping we can maybe bounce our way out, but it's very unlikely. We're just throwing around ideas right now.

So that will be it, tonight: the last-ditch effort to cause Philae to move into a position in which its solar panels will be able to recharge the batteries. Mechanical movements will drain power quickly, so if they do manage to move things, it seems almost certain that that will be Philae's last act unless the unlikely happens and these last-ditch efforts really do effect a major change in the power situation.

A lot of people have been asking me whether the tiny amount of sunlight reaching the solar panels now would be enough to recharge the battery, given enough time. Lommatsch put that idea to rest.

It is very unlikely right now. We have 1.5 hours [of sunlight] at less than 1 watt, and 20 minutes of 3 or 4 watts. The lander needs 5 watts to boot....In order to charge the secondary battery, we have to heat it to 0 degrees Celsius. We need about 50-60 watt-hours a day in order to reach 0 degrees and still have daylight left to charge the battery. So it doesn't look that great. What we could hope for is if we are closer to perihelion, near 1 AU, maybe we could have enough energy on our one solar panel, maybe every once in a. Having [a communication] link requires additional power again.

You can watch the whole Hangout here:

After the Hangout ended, Matt Taylor invited me to visit the Main Control Centre here, where I was able to shake the hands of just a few of the dedicated team that has kept watch over Philae 24 hours a day since Tuesday.

Emily Lakdawalla and the Philae team
Emily Lakdawalla and the Philae team

I had thought that this was going to be my last act here at ESOC, and that I would be monitoring the situation from my hotel room this evening. But it looks like I may get a chance to return to ESOC to be here while they wait for possibly the last contact they ever get from Philae. If I don't collapse first! Stay tuned for more.

 
See other posts from November 2014

 

Or read more blog entries about: Rosetta and Philae, mission status

Comments:

Messy: 11/14/2014 01:13 CST

Look at it this way, the last time this sort of thing was attempted, the lander MISSED and we got nothing. This mission was a howling success. Maybe it can jump away into the light, but they got plenty. Decades of 1,234% successes have made us spoiled. a "merely" perfect mission should make us frustrated or sad.

messy: 11/14/2014 01:14 CST

sorry I should have said "shouldn't".

Stephen: 11/14/2014 03:41 CST

@Messy "This mission was a howling success." It is important not to overhype what a mission achieves. That merely sets the mission (and the watching public) up for a letdown later on. Phila landed successfully, but its harpoons did not function in the way they were supposed to. As a consequence it went bouncing off to somewhere mission controllers have yet to pinpoint, but in place which has shadowed its solar cells and thereby prevented its batteries being recharged. It seems to have been able to do some science, but unless a miracle happens and it can recharge its batteries it will (probably) perish prematurely, which in turn will mean it will (probably) not achieve all the science it was supposed to or could have done. On that basis I would judge its success to be more mixed than "howling".

John: 11/14/2014 07:30 CST

Concur - any suggestion otherwise results from the slow release by ESA investigators of the stunning results they are getting. 15 years ago they started building a probe to land on an incredibly difficult and unknown place. Despite the fact that the comet turned out to be wildly different from anything anticipated - the lander reached the surface, functioned, and DID SCIENCE! But, since ESA is not releasing more than tiny bits of information the only thing to report on is what didn't work. Anyone not surprised that a nitrogen tank might have leaked after ten years in space; or that a few moving parts might be sticky. A truly amazing human accomplishment.

Rakesh: 11/14/2014 11:19 CST

Howling success...yeah right. Sorry, but thats a low bar. Less than 3 days after landing, the lander is about to die. A howling success would have been the lander dying when the comet approached the sun and water/pressure emanating from the still comet destroyed the functioning craft. Good effort by the scientists neeways.

Stone: 11/15/2014 03:19 CST

The slow release for most of the instruments for example of COSAC is that it takes some time to understand what exactly was going on and what the molecules are which we see in the mass spectra. There will be a lot of telecons next week to get a discussion going and in the end there will be a overview of what we found. The raw data is of no interest for all except a few people who have had a worked with MS data. I like too have several sniffing MS plots and one GC-MS on my computer to work with. I already got some e-mails from the science team with plots and suggestions what we see, so we work to provide what you want to see, but give us a little bit of time to get it right.

Torbjörn Larsson: 11/15/2014 06:43 CST

I went over to Nasaspaceflight.com, and got promising claims that the drill cycled, and that COSAC and Ptolemy, the vital volatile isotope measurements I take it, finished and there is some data delivered. But no promise that the drill hit anything, or that COSAC and Ptolemy see something if just the ambient, or that the data delivery is complete. @Stone: I'm amazed, but perhaps not surprised, by having data leaked so quickly. But it is also frustrating, since while the paying public have to wait for months until it is well understood and published, we could at least have a hint that the experiments see something at all. You managed to describe the status ambiguously, promising but not guaranteeing that scientists "see" something and "see ... molecules". Which is frustrating of course. The mere description of seeing mass peaks would be enough info for now, while I take it for granted that no one can guarantee if and how much information such peaks would give.

Torbjörn Larsson: 11/15/2014 06:50 CST

Oh, I forgot, and perhaps I am overinterpreting this, and the sources are not guaranteed: those threads I described in my earlier comment claimed that Ptolemy needed 20 V on the main bus. While providing an image of a dropping voltage curve that ends up with just about exactly 20 V... It may have been a tight squeeze!

David: 11/15/2014 08:00 CST

Stephen: "prematurely"? It operated for 58hrs or so out of 60 estimated from the battery and had every instrument do something (even if the APXS got to see the chemical composition of its lens cap) which is more or less what the primary mission dictated. After 10 years in space and a more craggy comet than originally planned for. Rakesh: primary mission == battery charge at separation =~ 60h. Stone: Good luck! Analysing mass spectrometer results is probably a bit time consuming, especially when you wish to make sure what you are seeing before informing the public. Good thing the drill went through the whole waltz and I suppose what many really wish to know is whether it drilled coma or something more solid. Well, as mentioned, there needs to be an understanding that such results will take some time. Torbjörn: I wasn't aware data had been leaked?

stone: 11/15/2014 08:56 CST

Torbjörn: I wasn't aware data had been leaked? David: I think Torbjörn thinks that the data I have is leaked. Torbjörn: I am part of the COSAC science team and the PI himself sent me an email with the data so it was not leaked. David: If we have coma or comet is not clear yet.

Emily Lakdawalla: 11/15/2014 09:00 CST

It took heroic effort for the science teams to develop new command sequences for the lander's surprising circumstances -- the team are entirely shattered. Yet they are having (or, I guess, have just had) their first science team meeting this morning to begin to discuss results. When I arrived, I predicted that we'd get some data down to the impact point, and then lose the lander. I really didn't expect results from the ground. The success of this mission is far beyond my expectations -- as measured in hours operated and data packets won. The science remains to be seen, and as stone says, GCMS work can't be done overnight. Be patient.

secure: 11/15/2014 09:49 CST

What I'd like to know is which of the experiments worked as expected, period. That obviously include whetever the drill actually reached the comet or not. But also things such as if, say, the landing leg experiments worked in the landing position it was (ie CASSE and PP)? Was the final landing position suitable for CONSERT (I know it was used, but was it a good place for it)? Was the second ÇIVA panorama with a different exposure time a success? And so on and so forth. But ultimately those answers will come when they come. What is a few days/weeks/months compared to 10 years? The fact that it even made it down made me happy by itself, the bounces just made this event even more dramatic and memorable. Sleep well Philae, job well done. Thanks for the coverage Emily!

Bob Ware: 11/15/2014 11:26 CST

Trying to move the spacecraft at this time is a great idea. It is a no lose situation. You can only win. If you hit more sunlight you win. If you don't then you still win since the spacecraft was going to be out of power need to function by that point. So try it. You can only win! ... again. This was a mission destined to fail based upon the appearance nature of comets that we have seen to date when this was launched. The fact that ESA pulled off a successful orbiter phase and a successful landing phase at all is phenomenally astounding! CONGRATULATIONS TO ALL OF THE TEAM MEMBERS FOR A JOB EXCEEDING EXPECTATIONS BEYOND ANYONE'S WILDEST DREAMS!!!!!! The next time this is tried will have what was learned here applied. Except for 1 of my coworkers, they are not really into space exploration but this mission on landing day had them all looking at the web.

Reb: 11/15/2014 12:13 CST

Emily, you've made this entire, historic event special beyond compare. Like you, we took a break away this morning. Just came on, read ESA updates, came to your blog and read about the MUPUS twitter account. At the moment we checked it, from a principle, totally FRESH RESULTS, FROM A wild rocky world beyond Mars........ >> From a MUPUS principle just NOW... "Around local noon direct sunlight on that wall caused a steep temperature increase...," diurnal temp results, "Data indicate low thermal diffusivity and fluffy substance." More tweets JUST NOW while writing this -- for you & readers to go see! Ms EMILY, YOU'VE BROUGHT US ALL into realtime contact with the highest orders of exploration on another world, unbelievable, eternally grateful and indebted TO YOU, MS LAKDAWALLA! And Plan Soc. @Stone or Emily, when will we know if it was comet or coma https://twitter.com/philae_MUPUS

Reb: 11/15/2014 12:23 CST

Shoot, is this mupus for real -- (if so, it's mindblowing). Regardless, massive congrats to you, Ms Emily, thanks for your very hard work, get some good rest back home.

Stephen: 11/16/2014 12:37 CST

@David "It operated for 58hrs or so out of 60 estimated from the battery" FYI, the lander had solar cells which would have allowed it to outlive its 60-hour battery life--if only it had come down in a place with better sunlight. Like I said in my original post, let's not overhype its achievements. Instead let us be glad and grateful it achieved what it did.

M.GOURAN: 11/16/2014 02:58 CST

Phila,you as a Ppioner in Cometary research ,happy birth day to you.

Stargazer: 11/16/2014 10:41 CST

To be honest, I was worried about the landing being successful at all. If only the harpoons had worked! But, for a first ever attempt, this worked out pretty nicely if not perfect. I also feel that it is high time for ESA to finally develop its own RTG units. They will need them anyway when they go beyond the asteroid belt in the future.

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