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Power Space Technology

Comet Probe Philae To Deploy Drill As Battery Life Wanes 223

An anonymous reader writes With less than a day of battery life left, The European Space Agency's Philae probe will begin to drill for samples even though the drilling may dislodge it. From the article: "Philae is sitting in the shadow of a cliff, and will not get enough sunlight to work beyond Saturday. Friday night's radio contact with the orbiting Rosetta satellite will be the last that engineers have a reasonable confidence will work. The team is still not sure where on the surface the probe came to rest after bouncing upon landing on Wednesday. Scientists have been examining radio transmissions between the orbiter and the lander to see if they can triangulate a position. This work has now produced a 'circle of uncertainty' within which Philae almost certainly lies."
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Comet Probe Philae To Deploy Drill As Battery Life Wanes

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  • Drill (Score:4, Funny)

    by Anonymous Coward on Friday November 14, 2014 @10:36AM (#48385275)

    Drill baby, drill!

  • by rolfwind ( 528248 ) on Friday November 14, 2014 @10:51AM (#48385371)

    Why was this designed to use mainly solar instead of a radioisotope thermoelectric generator like the voyager probes?

    A comet's trajectory out of the solar system would have been interesting thing to ride on, but then solar wouldn't be a viable option.

    • Re: (Score:2, Interesting)

      by Anonymous Coward

      Lander had to be as light as possible to make it out there with their expected launch volumes. The lander only weighs ~20kg.

    • Mass.

      An RTG is heavy. Solar panels are much lighter, and the comet is currently on a sun approach.

      • Re: (Score:3, Informative)

        An RTG is heavy. Solar panels are much lighter.

        Also: An RTG is expensive. Solar panels are much cheaper.
        RTGs are expensive to make, expensive to handle, and expensive to launch.
        An RTG would have likely doubled the cost of the mission.
        So if the budget is fixed, that means half as many missions, which is the same as a 50% failure rate, which is worse than solar panels.
        Also: RTGs generate political opposition. Solar panels don't. If this was an American mission, that wouldn't matter so much, but this mission is from nuke-o-phobic Europe.

      • Re:Solar? (Score:4, Informative)

        by Solandri ( 704621 ) on Friday November 14, 2014 @12:52PM (#48386479)

        An RTG is heavy. Solar panels are much lighter, and the comet is currently on a sun approach.

        According to Wikipedia [wikipedia.org], Philae's power system weighs 12.2 kg and generates 32 Watts @ 3 AU (approximately halfway between perihelion and aphelion).

        A SNAP-19 (1970s-era RTG) [wikipedia.org] weighs 13-15 kg and generates a constant 40+ Watts electrical.

        The comet's perihelion is 1.2 AU, aphelion 5.7 AU. Generally, Mars (~1.5 AU) is about the point where solar ceases to be cost-effective. Orbiters sent to Mars are solar powered. But landers (which have to deal with longer nights) have used RTGs when possible (Viking landers, Curiosity rover), with solar powered landers having a life expectancy of weeks to years.

        Given they were landing on a tumbling comet ((the comet has a 12.4h rotational period so the lander would experience a relatively lengthy "night"), and the perihelion being somewhere between Earth and Mars, this was probably a good candidate for a RTG. I suspect they weren't expecting the lander to survive past perihelion however (13 Aug 2015), which could have tipped it in favor of solar.

    • by Anonymous Coward

      Radioisotope thermoelectric generators (RTGs) are big, heavy, and emit radiation that screws up some of the instruments.
      The ones on Voyager are about the size of Philae. from Wikipedia: The GPHS-RTG has an overall diameter of 0.422 m and a length of 1.14 m.[1] Each GPHS-RTG has a mass of about 57 kg and generates about 300 Watts of electrical power.

      Philae:
      Launch mass 100 kg (220 lb)[1]
      Payload mass 21 kg (46 lb)[1]
      Dimensions 1 Ãf-- 1 Ãf-- 0.8 m (3.3 Ãf-- 3.3 Ãf-- 2.6 ft)[1]
      Pow

    • by idji ( 984038 )
      Europe wouldn't allow research and dev on such nuclear tech. (they asked this question in a Google hangout today)
      • Europe wouldn't allow research and dev on such nuclear tech. (they asked this question in a Google hangout today)

        Basically the leftists version of the rights stem cell research insanity.
        Remember: No matter what your political beliefs are, you can always use them to be stupid.

  • but it's running out of power...shit.

  • Is the shadow a permanent problem? Or will it potentially get back into the sunlight at some point as the comet reaches a different part of its orbit?

    • by sjames ( 1099 )

      They really aren't exactly sure where it is or what the surrounding terrain is like. It is quite likely that by the time the lander gets direct sunlight it will have failed due to prolonged cold.

      BUT, the gravity is extremely low and it's not tightly anchored to the ground, so it could (accidentally or on purpose) throw itself into a new location that might work better. They want to accomplish as many objectives as possible first because it could also face plant.

    • by Bongo ( 13261 )

      By that time the panels may be covered in dust anyway, I think they mentioned.

  • Astronomers Discover Planet Identical To Earth With Orbital Space Mirror http://www.theonion.com/articl... [theonion.com]
  • two bounces (Score:5, Interesting)

    by Thagg ( 9904 ) <thadbeier@gmail.com> on Friday November 14, 2014 @11:10AM (#48385527) Journal

    Philae bounced twice, the first bounce was about two hours, the second one 7 minutes. If the gravity on the comet is 1/200,000th that on earth (a reasonable estimate, it varies around the comet because it's *way* not round) then the first bounce was about 1,000 feet off the surface, but the second one was only about three feet. Seven minutes to fly up and down three feet; that's almost impossible to imagine.

    • The first bounce is pretty crazy to think about too. It landed, went 4cm into the surface, and bounced back up. It took an hour for it to stop moving away from the comet and start falling back down, and in that hour it only managed to travel about a kilometer. The entire thing is so otherworldly. Check out this picture [flickr.com], it might be my favorite so far. It's from 10km up and looks across the surface, and you can see a haze of some gas or dust plus the stars in the background. I've never seen anything th

      • by Thagg ( 9904 )

        It is fascinating that you can see stars and the comet surface at the same time; it shows how far from the sun they are. In no pictures from the moon can you see any stars.

        Right now the spacecraft is about 3x as far from the sun as the moon is from the sun, so the sun is only 1/9th as bright there. I suppose the cameras might have a bit more dynamic range than the film cameras of the late 60's. The comet nucleus might also be quite dark, but the moon is very dark as well (about 10% albedo.)

      • Re:two bounces (Score:5, Informative)

        by SternisheFan ( 2529412 ) on Friday November 14, 2014 @12:22PM (#48386205)
        This blog pic shows just how far that bounce was... http://blog.wolfspelz.de/2014/... [wolfspelz.de]
    • Seven minutes to fly up and down three feet; that's almost impossible to imagine.

      Yepp. You could probalby jump beyond it's gravitational pull.
      One sneeze and your away for the day.
      *Aaaachoooh!* ... oh noes! Help, I'm flying.

    • Philae bounced twice, the first bounce was about two hours, the second one 7 minutes. If the gravity on the comet is 1/200,000th that on earth (a reasonable estimate, it varies around the comet because it's *way* not round) then the first bounce was about 1,000 feet off the surface, but the second one was only about three feet. Seven minutes to fly up and down three feet; that's almost impossible to imagine.

      I've been watching this mission with a certain degree of anticipation for a while but I'm no space/physics nerd so I have two questions for those who are:

      1) How likely is it that anything will come of the drilling now that the harpoons that were supposed to hold the probe down have failed given the low gravity?
      2) Will the comet ever again come into a position that might cause the probe to get enough sunlight to do any worthwhile science?

      • by Thagg ( 9904 )

        1) There is/was a significant risk that drilling would push Philae off the comet again. Still, it's a risk worth taking; without the solar recharging ESA has only until Saturday before the batteries run out.
        2) The challenge is that either the lander is on its side, so the solar panels can't see the sun; or that the lander is up against a wall blocking the sun most of the time. They are considering possible ways of reorienting Philae; but it doesn't seem too likely. Also, without the harpoons or ice screw

    • by c ( 8461 )

      Seven minutes to fly up and down three feet; that's almost impossible to imagine.

      Insert union labour joke here

  • I think we've been spoiled by the various Mars missions, and having rovers lasting well beyond the expected lifetime. We should not assume that all missions will be like that. We should revel in the fact that the probe is working at all after 10 years in space, and that it wa sable to land on the comet at all.
  • by PW2 ( 410411 ) on Friday November 14, 2014 @11:33AM (#48385719)

    Drilling and have it become dislodged for an hour or two, hopefully landing in a better place sounds like a feature -- I hope they fire the harpoons a few hours before the batteries are discharged to take the chance of repositioning it in an open area

  • I only hope my final moments can be so bold. . .
  • From www.latimes.com/science/sciencenow/la-sci-sn-philae-lander-data-20141114-htmlstory.html

    Fifty-six hours after landing on the surface of a comet, Philae sent one more round of data about its new home across 310 million miles of space. Then, its power went out.

    "@Rosetta, I'm feeling a bit tired, did you get all my data? I might take a nap..." read a message on the @philae2014 Twitter feed.

    The Rosetta mission's twitter response: "You've done a great job Philae, something no spacecraft has ever don

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