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Power Space Technology

Comet Probe Philae Unanchored But Stable — And Sending Back Images 132

An anonymous reader writes with an update to the successful landing of the ESA's comet probe Philae, which (as mentioned yesterday) had problems attaching to the surface of the comet's Rosetta: "BBC now reports that Philae is stable on the surface. Although no source claims so, we can all imagine a faint humming of 'Still Alive' coming from the probe." Not just stable, but sending pictures while it can. From the article: The probe left Rosetta with 60-plus hours of battery life, and will need at some point to charge up with its solar panels. But early reports indicate that in its present position, the robot is receiving only one-and-a-half hours of sunlight during every 12-hour rotation of the comet. This will not be enough to sustain operations. As a consequence, controllers here are discussing using one of Philae's deployable instruments to try to launch the probe upwards and away to a better location. But this would be a last-resort option. New submitter Thanshin notes that the persistent Philae bounced a few times, and actually performed 3 landings, at 15:33, 17:26 & 17:33 UTC.Thanshin adds links to a handful of relevant Twitter feeds, if you want to follow in something close to real time: Philae2014; esa_rosetta; and Philae_MUPUS (MUlti PUrpose Sensor One).
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Comet Probe Philae Unanchored But Stable — And Sending Back Images

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  • Sideways (Score:5, Informative)

    by Thanshin ( 1188877 ) on Thursday November 13, 2014 @10:44AM (#48377637)

    Now Philae seems to be sideways and under the shadow of a cliff that only let's it have sunlight 1,5h per 12h cycle.

    That amount of sunlight may not be sufficient to keep Philae operating beyond its 60h battery autonomy.

    Most info seems to appear first in BBC news [bbc.com]

  • Why did we get away from that technology for space exploration? If you're going to spend the money to conduct a mission of this sort why limit yourself to the power provided by solar panels? It would be a pisser to have come this far only to have the mission fail because the probe can't get enough power to carry on operations.

    • by trout007 ( 975317 ) on Thursday November 13, 2014 @10:53AM (#48377693)

      They are still used but it's in short supply because you need to create it in special reactors. And funding is a problem.

      http://en.wikipedia.org/wiki/P... [wikipedia.org]

      • by Dunbal ( 464142 ) *
        Could always ask North Korea for some. Oh wait, yeah, sanctions, my bad.
        • by Hadlock ( 143607 )

          France operates a number of breeder reactors that could be repurposed possibly. Since the Regan administration (in fact, Regan himself) we've lost the capability to manufacture Plutonium in abundance. Not that there's a lot of use for the stuff but the supply is running low as is it's half life.

    • by mc6809e ( 214243 )

      Why did we get away from that technology for space exploration? If you're going to spend the money to conduct a mission of this sort why limit yourself to the power provided by solar panels? It would be a pisser to have come this far only to have the mission fail because the probe can't get enough power to carry on operations.

      Two reasons: fear that an accident might release plutonium dust into the atmosphere, and the relative shortage of plutonium.

    • I don't know how much heat an RTG emits, but if you're trying to land on a comet, it would be a real pain if you melted away the surface you had landed on.
      • by amorsen ( 7485 )

        You are lucky to get 10% efficiency from an RTG with a thermoelectric element, and proper Stirling engines or steam turbines are not popular in space for some reason.

        However, Philae only needs 32W apparently.

        • You are lucky to get 10% efficiency from an RTG with a thermoelectric element, and proper Stirling engines or steam turbines are not popular in space for some reason.

          I presume that reason is water weight, in the case of steam turbines, and the lack of free atmosphere to work with in the case of stirling engines. If you could somehow get the water there, though, a recirculating steam system seems perfectly cromulent. Certainly the system efficiency is dramatically better than an RTG, and it doesn't require any especially exotic materials.

          If you had unlimited mass to work with (ha!) and you were using water for reaction mass anyway, it might actually make sense. Not here

          • I presume that reason is water weight, in the case of steam turbines, and the lack of free atmosphere to work with in the case of stirling engines.

            A Stirling engine doesn't require an atmosphere - all the gases are sealed inside and they are "external combustion" engines - just apply a heat source to one side, allow the other side to radiate heat, and away you go.

            • Actually there is such a thing as an internal combustion Stirling engine. The British military deployed a portable generator set during WW2 that used one, and the google will disclose a few more. Obviously not much good in space, of course.

          • ... We could have built a pretty big station out of the space shuttle main tanks, for example.

            We sort of did, actually, back before the space shuttle. See "SpaceLab", I think it was. But it's hard to get them high enough, and it fell back years ago.

        • by necro81 ( 917438 )

          proper Stirling engines or steam turbines are not popular in space for some reason

          R&D on a nuclear-powered stirling engine for space [wikipedia.org] is ongoing [wired.com]. It's not they they aren't popular, per se, its just that they are a very difficult engineering problem. How many devices with continuously moving parts do you know that operate maintenance-free for years or decades? It's not impossible, but is really hard.

          • by tlhIngan ( 30335 )

            its just that they are a very difficult engineering problem. How many devices with continuously moving parts do you know that operate maintenance-free for years or decades? It's not impossible, but is really hard.

            That's the big problem. Mechanical devices wear down, and even without maintenance, going for years is difficult. Think of things like your hard drive bearings, or fans that work for years without maintenance, but having them work for a decade is a more iffy proposition reliably.

            Plus, there's also

        • by radtea ( 464814 )

          proper Stirling engines or steam turbines are not popular in space for some reason.

          Stirling engines are used in space, but only when there is a compelling reason to do so. The basic argument against them is two words: moving parts.

          Mechanical wear is a huge problem, and thermal management is not a small one. Depending on the spacecraft a sustainable thermal regime may have to be maintained across very different environmental conditions (full sunlight, deep shadow) and very different operational phases. Just getting lubrication to work properly under such circumstances, over a decade in the

          • by amorsen ( 7485 )

            I was being facetious, I thought that both ideas were so ridiculous that it would be obvious to everyone why no one does that.

            Obviously I was wrong about Stirling engines. Perhaps I will end up wrong about steam turbines too one day.

      • by Dunbal ( 464142 ) *
        A good engineer would take advantage of this and include this feature as part of some experiments.
    • by amorsen ( 7485 )

      Rosetta/Philae came back to Earth several times for gravity boosts. It would not take much to make those flybys into direct hits, probably turning the RTG into radioactive dust.

      Agencies who are dependent on public funding are generally wary about spreading radioactive dust.

      • Several probes with RTGs have made close Earth passes. As I recall, Cassini happened to pass low over Iran for its final boost outward.

        • by amorsen ( 7485 )

          Indeed. There was protests about that, and that was just a single pass IIRC. It is just not worth the bother unless it is the only way to accomplish the mission.

    • by Sperbels ( 1008585 ) on Thursday November 13, 2014 @11:03AM (#48377797)
      I'm sure that wherever you're from Plutonium is available in every corner drug store, but for us it's a little hard to come by.
    • by asylumx ( 881307 ) on Thursday November 13, 2014 @11:45AM (#48378167)

      It would be a pisser to have come this far only to have the mission fail because the probe can't get enough power to carry on operations.

      Who said the mission would be a failure? They've landed on a comet and received lots of data from the lander already. Even if the mission is cut severely short, it sounds like a success to me.

    • by necro81 ( 917438 )
      As others have mentioned: RTGs are difficult to come by ($$$, rationed resource) compared to solar panels. Generally, they only get used when there is no other way to power the spacecraft to meet the science objectives.

      The present RTG designs for spacecraft are all 1-2 orders of magnitude larger than what Philae would need.

      One other thing I would note is that RTGs have useful lifespans measured in years to decades. Philae hasn't been designed to operate for that long (its long sleep until it arri
    • by hey! ( 33014 )

      Why? Because solar panels will do the job, where the job needs to be done. Simple as that. All the interesting stuff is going to happen when the comet is near perihelion, which for 67P is 1.2 AU. There's plenty of solar power there.

      At 67P's aphelion of 5.7 AU an RTG would be needed -- if there were any observations worth spending money on. But powering this spacecraft with an RTG would be sending an expensive and heavy piece of equipment out into the middle of nowhere for no good reason. It'd be differe

    • Because of the nuclear fear mongers. "All radioactive material is EVIL!!!".
  • "Unanchored But Stable — And Sending Back Images"? Let's call the next comet probe "Kim Kardashian". Then again, Philae is stable.

  • ESA has three successful landings on a comet now to brag about.

    Using the same lander, on the same comet. Cheaters.

  • by Anonymous Coward

    "The lander weighs about 220 pounds and is the size of a domestic washing machine"

    I'm waiting for the Saturday Night Live skit..

    Due to a terrible mix-up. a Maytag washing machine was inadvertantly placed in the cargo hold of the Rosetta spacecraft.

    "My socks have been missing for 10 years!" said Matt Taylor. He also added that now he knows why the washing mashine in Mission control does such a horrible job on the rinse cycle and has stymied the Maytag repairmen/women for the last 10 years.

    "In hindsight we s

  • by tibit ( 1762298 ) on Thursday November 13, 2014 @11:20AM (#48377941)

    At the moment, the Philae mission is a partial, or qualified, success. They'll be receiving the passive science data and imagery, but let's be realistic: they have no way of anchoring Philae to the comet, they can't drill, and any attempts at "bouncing" it are at the mercy of how much gyro range is available to keep it stable while it follows the ballistic arc - and whether it'll come down anywhere safe enough to keep itself upright. The gravity is so small that the lander could "impact" the comet upside down and it wouldn't damage it, it'd just make its orientation useless for the deployment of drilling instruments. Heck, it may be that the gyros have enough oomph to roll the Philae if it ends up upside-down, although it'd probably tumble for a while before setting in some other random orientation, possibly still a wrong one.

    They have to weigh the battery life against science returns - and right now there's no battery recharging to speak of. That's the hard part of rocket science - it's not through any fault of mission design, it's simply a bad luck. So, I bet they'll keep Philae where it is up to say 48-50hr mark, and then they'll re-enable the gyros and attempt a bounce, and they'll get one shot at it due to the time the bounce will take, and the link availability constraints due to Rosetta's orbit. I really wonder if the harpoons didn't work due to insufficient contact forces and a sequencer step to shoot the harpoon not being triggered, or if it's due to a failure of the harpoon deployment mechanism itself. It wouldn't hurt to reattempt a harpoon firing once the bounce ends with a recontact.

    I'm still wondering why they couldn't get the Rosetta spacecraft itself to be the lander. It's a much bigger platform, it has a proper RCS system and could easily land and take off to scout multiple locations on the comet. Not having a stand-alone lander would give enough available weight to put the instruments on Rosetta itself, and take the extra fuel to do repeated landings and take-offs. That's at least according to my back-of-the-envelope fuel budgeting, I may be way off, though...

    Overall, the biggest lessons learned are about things didn't work. Any further low-gravity comet lander designs will need to use designs that include fixes for whatever didn't work this time. I really wish they did, for example, store a duplicate thruster fuel supply system on Earth, in cryogenic conditions, for the decade Rosetta was out there - I bet it'd fail on Earth just as it failed out there, and it'd be an easy thing to post-mortem. But that time has passed, so we may never know what went caused the failure of the puncture pin system...

    • by onepoint ( 301486 ) on Thursday November 13, 2014 @11:39AM (#48378113) Homepage Journal

      The problem is: we are talking about a design area of 1995 to 2002, with flight in 2004.
      So, what we can do now, is all based on what we have learned.
      All your ideas are valid and we will be better at it in the future.

    • I'm still wondering why they couldn't get the Rosetta spacecraft itself to be the lander. It's a much bigger platform, it has a proper RCS system and could easily land and take off to scout multiple locations on the comet.

      Bigger means more vulnerable to rough terrain, and we really knew nothing about the terrain on the comet when the probe was launched. (And actually, we only have a sample size of one, now.) Making the whole spacecraft a lander also puts the entire mission at risk in the event of a landin

      • Going all in on the first try of mission already fairly risky

        A lot of problems do seem to be caused by trying to do to much in unknown environments. A Russian Mars lander in the early 70's even had a little rover. This was before anybody knew what the surface of Mars was even like: rocky? sandy? dusty? If they focused instead on making it simple and robust, they could have had the first successful landing.

        Same with UK's Beagle lander. If they had made it simpler and smaller, they'd have enough money left ov

  • Black and White? (Score:3, Interesting)

    by canadiannomad ( 1745008 ) on Thursday November 13, 2014 @11:28AM (#48378031) Homepage

    I have a question... Does anyone know why are the photos in black and white? Is that for higher resolution, because of low/high light situations?

    Ok nvm, found my answer here: Why are images from space probes always in black and white? [straightdope.com]

    Still think they should take photos with RGB filters too so we can see what it would actually look like, you know, for PR photos...

    • by tibit ( 1762298 )

      There's nothing colorful on a comet. It's just shades of gray. Seriously. It's literally dirty ice.

      • I realize that, but then what colour is the ice? What colour is the dirt? This isn't for science, it is for general interest.
        I realize that using the filters they have they can create enhanced colour images, and I think that might be exactly what they should do...
        Do you really know it is grey? Ice can have some pretty amazing light distortion properties(go visit Alaska)... And not all rocks are grey.

    • You can do the same thing with a single B&W image and processing back here on Earth; without having to send that extra kit into space. It was good enough for Ted Turner....
    • Still think they should take photos with RGB filters too so we can see what it would actually look like, you know, for PR photos...

      No doubt they will, if they have time and power. But they're sharply limited on both, and I doubt the color images actually have all that much more PR value. (Not that PR has ever been shown to translate into actual public support mind you.)

    • by Lumpy ( 12016 )

      ted turner hasn't colorized them yet...

  • by Qbertino ( 265505 ) <moiraNO@SPAMmodparlor.com> on Thursday November 13, 2014 @11:43AM (#48378149)

    This [flickr.com] is so cool [flickr.com]. ... Isn't that freakin' amazing? ... I'm getting goosebumps all over and feel like back in the 70ies when we'd been to the moon. (my Grandpa worked at Grumman as a Engineer on the Lunar Lander btw.)

    We've landed on a friggin' Comet! This is so awesome!
    F*ck yeah! YAY! Go, space exploration, go!

    • I'm feeling the same way. You know that scene in The Lego Movie where Benny finally gets to build a spaceship and he builds/flies it while shouting "SPACESHIP!!!" as loud as he can? I feel like doing that only shouting "ROBOT ON A COMET! ROBOT ON A COMET! ROBOT ON A COMET!!!!!"

    • I'm with you, dude. I didn't really think much about this one, until I saw that first image you link to. That is when it hit me: I have never in my life seen anything like this before, ever. I have seen things "as cool" (V'ger, Galileo, Cassini) but nevertheless, they weren't this.
  • While it's not Math, we will add more knowledge to the simulations, we will learn a lot of the bounces, which should teach something about gravity bouncing on asteroids. We just might discover that the "dust" was really frozen solid, we might learn how to glide better.
    They did something that was very improbable (speed matching at amazing speeds) which now makes it possible. I can not wait for the future

  • On the bounce, while the Roseta is bob, bob, bobbin' along... keep bouncing.
  • by codepigeon ( 1202896 ) on Thursday November 13, 2014 @11:56AM (#48378261)
    Those aren't pictures from the surface(as of right now). They were taken by rosetta from orbit.
  • Fixing something like this is just his style.
  • This is an amazing shot in my opinion, like something out of an early 1960's sci fi show:

    https://www.flickr.com/photos/... [flickr.com]

    With some image processing it can probably get even clearer. We are seeing the rawer early versions.

    The spewing "jet" ones are also interesting, but do look similar to past Enceladus images. The difference in this case is that they are probably only a few miles away from the probe instead of a few thousand.

  • paste from Reddit... (Score:5, Informative)

    by SternisheFan ( 2529412 ) on Thursday November 13, 2014 @03:03PM (#48380199)
    Got fresh news from the team, they are broadcasting live right now on french TV ! Philae landed, and bounced slowly for 2 hours, and travelled 1km away the targeted site. Yes 1000m. It's now stopped slanted, some cams are shooting the sky, other the ground, and other nearby rocks, as seen on the first photo. It's inside some kind of hole, not much sun for the solar panels. EDIT1: It landed on the core of the comet, it sees the light from the sun for about 1 to 2 hours per day. In the next days/week the angle of the comet will change relative to the sun, and it very likely the solar panel will get more sunlight so more power for the probe. EDIT2 : Many labs are performing right now and performed the whole night. For now they put the drilling on hold since they don't know if it's tied to the ground or not. Drilling op is also power hungry so it's kinda a good thing it's on hold since there's not much sun available for the panels. Battery life been re-estimated to 50-55hours due to the lack of sunlight. This includes the 7 hours of descent.They are constantly adjusting missions goals, depending on conditions, power available, etc, EDIT3 : The probe has been working to gather scientifict data the whole time, including during the bounces. There's already a large amount of data available, whatever happens next.

    EDIT4 : It's resting on "hard" ground, with a layer of dust about 30cm, and that's good news because it allows measurements to proceed as planned. As in, it's not burried into soft soil.

    EDIT5 : Solar panels are deployed, radio link is up and running, but the fact the probe is slanted/in a hole/random ground limits the time it can communicate with the orbiter, altho that's not jeopardizing the mission. There's already a lot of things transmitted successfully to the orbiter. Contact between the orbiter and the probe can be done twice per day. EDIT6 : The first place it touched the comet was exaclty where it was planned, flat and cosy, too bad it didn't harpoon there. EDIT7 : Next contact will be near 19:30GMT, until 23:45GMT approx. This night they made contact with the probe (from the orbiter) at about 4:00GMT, and at 5:30GMT they had safely recovered all the data from the first batch of tests. From the ESA blog :

    The team are ensuring that Rosetta maintains an orbit that is optimised for lander communication support; they are planning a manoeuvre (thruster burn) today to be conducted on Friday that will help keep Rosetta where it should be. Rosetta already conducted a burn last night as part of this effort.

    Rosetta is presently sending signals to the ground stations at about 28 Kbps; Ignacio says that the spacecraft's own telemetry downlink uses about 1 or 2 Kbps of this, so the rest is being used to download science data from Rosetta and lander science and telemetry from the surface.

    Important press conference from ESA at 13:00GMT. Over now. http://rosetta.esa.int/ [esa.int] EDIT8 : So there was more photos, and details. Important bit, they're planning on righting the lander, studying the best way to do it. First rebound was about 1000m long, 0.38m/s up, lasted 2 hours. 2nd rebound was 0.03m/s, 7 minutes long. Then it stuck itself in the side of the crater at the 3rd impact.

    EDIT9 : Harpoons received the signal to fire, but didn't activate. There's no indication of damage on solar panels. The lander can hibernate and may likely still work several monthes from now, even if under limited power. They confirmed the orbiter will make adjustement tomorrow morning (friday) to optimize communication time with the lander. Operations are prioritized, from the less risky to the most.

    permalink

  • First bounce was 1000m up (from the surface) - that's a helluva hop.

    Then again, that was pretty much my result every time I tried to play Lunar Lander too.

  • Those pictures are amazing! I immediately was taken back to playing Super Mario Galaxy and imagined Mario running around the comet.

    -Chris

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