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Space & Planetary Science

The Little Comet Lander That Could

By Keith Cowing
NASA Watch
November 17, 2014
Filed under , , ,

Osiris Spots Philae Drifting Across Comet 67P/C
“These incredible images show the breathtaking journey of Rosetta’s Philae lander as it approached and then rebounded from its first touchdown on Comet 67P/Churyumov-Gerasimenko on 12 November 2014.”
Philae Spacecraft – robotic european space agency (ESA) lander, eBay
“Highly complex spacecraft with on-board laboratory, solar panels (requires sun), inter-stellar communications pack. Power system, Thermal control system, Landing gear, Anchoring system (faulty). Buyer must collect item from it’s storage location on Comet 67P.”
Why we all fell in love with Rosetta’s Philae lander, Washington Post
“By Friday night, we knew it was coming to an end: That morning, Rosetta scientists had told the public that Philae’s batteries were almost certainly going to die during their next communication link with the probe. And sure enough, Philae’s Twitter account followed through until the end, tweeting out a series of messages about going to sleep that made many (myself included) express grief for – and immense pride in – the little lander that could.”

NASA Watch founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

51 responses to “The Little Comet Lander That Could”

  1. dogstar29 says:
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    The teams supporting robotic exploration have done an admirable job of anthropormorphizing their spacecraft.

    • Michael Spencer says:
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      remember Opportunity and Spirit?

      • dogstar29 says:
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        They served as the focus for the determination and skill of their support teams and the aspirations, hopes and frustrations of their many fans. In many respects the rest of society reacted to their accomplishments as if they were human. That doesn’t mean humans shouldn’t fly in space, but where it isn’t practical for us to go in person, robots can do an excellent job.

  2. Michael Spencer says:
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    Where are all of the ‘robots can replace people for exploration’ people?

    • Paul451 says:
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      The entire ESA budget is less than NASA’s HSF budget. So yes, Philae achieved vastly more than you could buy by flying human missions with the same budget. If you don’t like that, you need to work to make HSF cheaper until it costs no more to send humans than to develop and send a robot. After that point, flying humans would be the best choice. Today, it is just pouring money down the drain.

      A purely robotic comet sample return mission would be a rounding off error in the SLS/Orion budget necessary for the ARM proposal.

      [Back on topic, fantastic shooting by Osiris. Here’s the hi-res.]

      • Michael Spencer says:
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        Oh dear. What I meant to say is this: see what ESA has done with a pittance? Stunningly effective and creative science? Sans humans? This project puts a bit of a cramp in the notion that humans are always better.

        More data would have been available with a couple of rock hounds out there, true; but in “euros/science returned”, the robots are in the lead. By a wide margin.

        Shoulda been clear.

      • mfwright says:
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        > “flying humans would be the best choice.”

        there was a time when flying humans was better than robots but robot tech advanced so it becomes more difficult to argue HSF. In meantime going to comets, asteroids, and Mars is best with robots (distances plus radiation too great for humans).

        Back on topic, I remember there was a time nobody knew what a comet or its surface really looks like. But I wonder when comet is closer to Sun, will there be geysers shooting water vapor all over the place? Difficult for a lander, difficult to get photos? OK, so I haven’t read that much of this mission or knowledge of comets but I spent some time just looking at that hi res image thinking what would the surface feel like.

    • stonemoma says:
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      Hi Michael
      it is good to hear that you are on board the next 10 year mission for sample collection from a comet. In the 10 years you can easily make you phd in geology and be the first expert on a comet.

      This mission is impossible for humans in the next few decades, so should we not do what we can do only because there must be humans doing the job?

  3. Jafafa Hots says:
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    As an ebayer, that one seller was not putting things in the most positive light. He should have said “Anchoring System” (never used!)”

  4. Mark Madison says:
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    Learning the dangers that apply to landing and or working on a low gravity object. NASA wants to sent astronauts to a ultra small low gravity asteroid.

    • Antilope7724 says:
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      With the extremely low gravity, this should have been more like a docking than a landing. Then maybe Philae wouldn’t have bounced.

  5. stonemoma says:
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    To be part is very exiting, a lot of people were very nervous before the landing, but now most of them had the first few results and are more relaxed.
    But still everybody wants more time with the instruments on Philae. I hope the sun will shine one day on Philae and that we will have a few mor GC-MS runs.

    • DTARS says:
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      Shame the little lander didnt have a nuke battery on board. This is case study for nuke power in space. Poor design decision to depend on solar power on an expensive exploration mission.

      • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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        it’s the other way around, it was a very good design decision that didn’t waste the very limited amount of plutonium 238 we have. Philae / Rosetta were launched a year late and had a 10 year trek through space before arriving at their destination. the RTG’s thermocouples would have experienced significant degradation by that point. it may not have been functional.

        that aside, nobody knew if the lander would even work. why waste plutonium on a probe that might crash, bounce off, short out, roll down a hill, etc?

        no, solar panels were the best power source for the mission.

        • stonemoma says:
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          The missing RTG has several problems which were not solved or will never be solved:
          *ESA and European politicians are not willing to go through the uproar of activists if plutonium is built into a spacecraft
          *ESA has no RTGs so they need to take a lot of money to design one
          *ESA has no way to get the plutonium and build a production facility is no option

          If you do not have the money, lack the materials and also have no political support you need a wonder to get what you need in time.

          • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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            what missing RTG?

            according to the information i’ve found the ESA plans to use Am-241, not Plutonium

        • disqus_wjUQ81ZDum says:
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          Trivia fact. Europe is working on their own version of an RTG. Fuel is Am-241.

          • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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            That’s interesting! I know that the ESA didn’t have an RTG program when Rosetta was launched, but the idea has been kicking around for a while. when did that RTG program start up?

          • disqus_wjUQ81ZDum says:
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            It started up a few years back. If you are interested, look up “Development and Testing of Americum-241 Radioisotope Thermoelectric Generator Concept Design and Breadboard System”, R. Ambrosi, et al.

          • Yale S says:
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            The major issues with the Am-241 RTG is the occupational exposure working with a seriously fierce gamma emitter with some major neutron and alpha emissions.
            Even more, those same emissions would interfere with the instruments unless quite massive shielding were used. Philae had a very low mass budget available.

          • disqus_wjUQ81ZDum says:
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            Since they are still a long way away from an RTG, I don’t see where it is an issue. Besides most people would recognize that an RTG on the lander just wasn’t practical. As for the emissions, I would suppose that Dr. Ambrosi and his team are designing the appropriate fuel containment system and handling safeguards will be put in place. His estimates for a 10W unit would have the approximate dimensions of 220mm x 190mm with radiator fins projecting around 160mm from that body.

            Am-241 produces somewhere around 59 kev gammas. Tungsten encapsulation, perhaps in conjunction with a boron loaded polyethylene if needed would be more than ample (but that would be very bulky). The people at MSFC seem to think Am-241 is viable.

          • Yale S says:
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            Even low emission rates are sufficient to swamp some detectors.
            RTGs are often placed on long booms which may be a problem on featherweight landers.

            The Solar panels supply 32w(e) peak, charging a 140 (160?) watt-hour (something like that) battery. the single use battery was 1 kwh with a 60 hour discharge – maybe 15-20 watt(e) continuous.

            I think most 241Am designs are about 2.2 watts(e) per kilogram (using a 10 mm lead shell and no neutron shield) or about 8 – 15kg RTG for Philae, not including power conditioning and management systems.

          • disqus_wjUQ81ZDum says:
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            I don’t know where you got your solar panel output for the lander, but the output is listed as not exceeding 10W on a daily average (“The Rosetta Lander Investigations”, J. Bibring, et al, Philae Project Office).

            And again, the idea of an RTG for the Rosetta mission was discarded back in the late 90s, so I really don’t get your point.

            NASA NIAC studies have shown AM-241 as viable. In studies with the now mothballed ASRG, it was concluded that using Am-241 GPHS modules vs Pu-238 reduced power output by about 1/5 while maintaining approximately the same system mass. However, there is no debate that Pu-238 can generate more energy per kilo and is more efficient. That is unless you want a mission to last for a very long time.

            Besides, I doubt the US would ever swing over to Am-241. Too many issues in the environmental area. As for the Europeans, I leave it into the professionals’ hands that are conducting the research that they are taking into consideration all the factors.

          • Yale S says:
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            I don’t know where you got your solar panel output for the lander, but the output is listed as not exceeding 10W on a daily average

            The key word is average.
            As I wrote: “The Solar panels supply 32w(e) peak” The comet rotates. The panels are 50% of the time in night darkness and during the day only produce peak power with the sun directly overhead a panel. Since the panels are wrapped around the craft, the output is somewhat complex. The averaged daily output (which fills the batteries) is 10 watts. Here is an graph of an Earthly rooftop PV array:

            http://blogs.scientificamer

            the idea of an RTG for the Rosetta mission was discarded back in the late 90s, so I really don’t get your point.

            This is a thread about the potential for using RTGs on Philae. So I’m discussing it.

            NASA NIAC studies have shown AM-241 as viable.
            I agree (if you actually want to use RTGs – I have extremely mixed feelings about them). The biggest issue is the managing the dangerous exposure to gamma and neutron radiation with Am-241 during extraction, manufacturing, and use. Pu238 is also extremely nasty in its own way.

          • disqus_wjUQ81ZDum says:
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            I would suggest “Production Experience with Hi-ETA/NR-LILT Silicon Solar Cells for ROSETTA Qualification”, Strobl as a better guide for the lander’s solar panels.

            Somehow, I think that the National Nuclear Lab (UK), which holds the current contract for processing the Am-241 for the ESA, will probably know what it is doing with regards to safety, etc. They are processing around 250kg of old plutonium (10-14% Pu-241) to yield around 10kg of Am-241. They’re utilize the method that dissolves plutonium dioxide in a silver catalysed process. The NNL is looking to make Am-241 a significant UK export.

          • Yale S says:
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            I’m not sure why you are referencing a short paper on testing the quality of a production run of the solar cells, unless just adding to the technical details of the discussion, which is fine.

            An interesting issue with extracting Am-241 is the motivation – beyond simply producing a galaxy of smoke detectors.
            Enormous amounts of (unfortunately) reprocessed spent reactor fuel plutonium is backed up in Europe. Some is blended in standard uranium reactor fuel (the blend is called MOX). One (of many, many) problems is that the Pu-241 in the spent fuel decays into Am-241. Am-241 is a nasty gamma ray emitter. After 6 years the reprocessed plutonium is so dangerously contaminated that it is not used in MOX. It needs to be washed out, creating yet more waste, occupational exposure, and more chances for weapon’s diversion.

          • disqus_wjUQ81ZDum says:
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            So where did you pull 32 watts peak from?

  6. Michael Spencer says:
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    Yesterday I had occasion to measure the diameter of a bar of milled steel without a micrometer or other appropriate device. I wrapped a piece of tape around it, then removed the tape and measured the length, thus calculating the diameter.

    “How did you DO that?”, said the person needing the data, a person with a college education. “C=Pi * D, remember from high school?” I told her.

    “I’m not so good at higher math”, she said. “Pi”?

    Argh. THAT is why objects are made into little people.

    • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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      some people just don’t like or aren’t good at math. or they just forgot everything they learned in geometry class, high school feels like a really long time ago…

      • Michael Spencer says:
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        I get your point, Doug, but isn’t there a ‘floor’ of some type that defines an educated person in a modern technological society? Stories about not knowing how to use a ruler or–wait for it-I was a liberal arts major and even I know about integrals (from taking a calculus class in high school). I maintain that the level of basic knowledge has just gone through the floor.

        • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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          overall i think i agree with you. i don’t think there is a common base of knowledge that defines an educated person, at least not anymore. in our society, where everyone is made to be “educated” and “literate,” i think that floor gets lower as the education gets watered down to make sure everyone is “educated” and “literate.” so there’s some negative feedback there, although of course, you only get out of your education what you are willing to take from it. and another part of the problem is that there are a lot of fields that don’t require more than basic math. as useful as it is, few people have much need to use geometry or algebra for anything, let alone calculus. also, if you DO need to use such things, you don’t need to remember them. each of us has a device in our pockets that can access all of the accumulated knowledge of humankind. and also there are a lot of very highly educated people that, outside of their field of specialty, are pretty much as dumb as a box of rocks. for a well known example, see Dr. Michio Kaku, a theoretical physicist who has gone on record saying a LOT of nonsense about things he really doesn’t understand, for example, things like dramatically overstating the radiation hazard from Fukushima.

          i think i may have gotten off track, but as a personal example, i’m pretty sure the only time i’ve used algebra since high school was when i was figuring out how common core math works.

          • Yale S says:
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            What specific numerical statement of Kaku’s about the radiation hazard from Fukushima is incorrect.

          • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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            as far as i know he never made statements about the quantity of radiation. he just made a number of inaccurate, fear-mongering statements along the lines that the entire world would be irradiated, which is why nutjobs who claim that the entire pacific ocean is poisoned with radiation quote him so often.

          • Yale S says:
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            The Japaneses were incredibly lucky (as bad as the on-going contamination is) due to the winds.
            Each reactor core contains the radioactive fallout of the simultaneous detonation of 1,000 Hiroshima atomic bombs. The spent fuel pools carry enormously more. Because the winds blew strongly offshore (west to east), more than 80% of the radioactive plume blew out to sea. The hugely contaminated liquid contamination was partially trapped, and much was (and is being) discharged into the ocean, with some very nasty local effects. (Imagine if that was a major US river..) The Pacific is large enough to buffer the US from significant contamination.

            If any of the reactors on Japan’s west had been affected it would have been a horrendous disaster.

            Luck also happened during the Chernobyl disaster. Due to the winds, the plume blew over forests and open land, missing the sparse local population. Even then 1,000s of cancers were triggered and there is still agricultural restrictions at a distance equal to New York to San Francisco.

            For comparison, NY and NJ has millions of people located near (within 50 miles) the Indian Point plant.

          • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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            that’s nice. thanks for the story, yales.

          • Yale S says:
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            Sorry, I tend to jabber on forever. My wife learned to tune me out long years ago.

          • hikingmike says:
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            He makes money doing that kind of thing. Seeing him in short interviews on a couple TV shows gave me the impression he leans toward big ideas with not much concrete behind them. There’s nothing wrong with that. When I hear advertisers for the local speaker series, he’s included as “futurist” Michio Kaku.

          • Yale S says:
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            He is pretty concrete with 70+ published peer reviewed physics papers.

            Its fun listening to one of his weekly radio shows:

            http://mkaku.org/home/radio/

          • hikingmike says:
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            I would tend to put his physics research into a different category than the stuff we’re talking about. I’m not saying those aren’t backed by concrete research. The “best” physicist can still say outlandish things outside his or anyone’s field of expertise.

          • Yale S says:
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            Ok, I see now what you were meaning. I agree. His views outside of physics are not necessarily any more insightful than anyone else’s. However, he is well informed and intelligent and his non-phyz ideas are at best spot-on, and at worst provocative and challenging. Always worth a read or a hear.

          • hikingmike says:
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            Yeah that’s it. I agree. It’s cool to hear from someone like him what “might be” in the future. Maybe I should go to one of his speaking dates I hear about on the local radio when those come around.

    • Yale S says:
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      Back when the the earth’s crust was still cooling, I briefly was a science teacher.
      First day of classes one year I wanted to start with a hand’s on activity. I asked each student to take a ruler and measure the length of their thumb and post the results. We would then graph a bell-shaped curve and slice and dice the data by gender, age, etc.
      Well.. not a single 7th grader knew how to use a ruler!
      I was stunned. They gone thru 7 years of formal education and never, not once had been required to measure anything.

      • Yashmak says:
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        A ‘ruler test’ is part of the hiring process at the aero company I work for. You’d be amazed how high a percentage of prospectives it disqualifies. . . or given your experience with the same phenomenon, you might NOT be amazed.

    • korichneveygigant says:
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      when I was in college my calculus professor wouldnt let us use any type of calculator to solve problems. To this day I am grateful to him for that. Many of my coworkers have trouble solving really basic stuff like that. A new hire (engineer) once asked for help solving a double integral. SHEESH

    • David_McEwen says:
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      Last week I tutored a community college student who didn’t know how many quarts were in a gallon. Seriously. In fact, he didn’t know *anything* about liquid measure conversions. I don’t know how such a thing is possible, but there it is.

      • Jay says:
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        To be fair, I’m confident if you did a ‘Jay-walking” (Jay Leno) a high percentage of adults would have to think about the quarts/gallon question. Our U.S. system of measurement is not the most user friendly. Perhaps we should start a government office to get the general public on the metric system? Oh wait, we did that in the 60s, fail. 🙂

  7. Chris Clardy says:
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    Perhaps we could learn a thing or two from ESA, Rosetta’s Waltz by Vangelis is a nice way to waste 2 1/2 minutes.

  8. Chris Clardy says:
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    Rosetta’s Waltz

    http://www.youtube.com/watc

  9. Michael Spencer says:
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    I wonder about the bouncing and if it was expected, or if the non-functioning harpoons were supposed to limit the bounce.

    • disqus_wjUQ81ZDum says:
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      They couldn’t pressurize the downward firing thrusters. That would have limited the recoil.