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Space Science

Beware the Rings of Pluto 96

Posted by Unknown Lamer
from the why-not-send-two-or-three dept.
Hugh Pickens writes "The Christian Science Monitor reports that scientists are planning a new route for NASA's New Horizons space probe as it approaches a potentially perilous path toward Pluto through a possible set of rings that may create dangerous debris zones for the NASA spacecraft. New Horizons is currently about 1,000 days away and 730 million miles from closest approach to Pluto but given that New Horizons is currently zooming away from the sun at more than 33,500 mph, 'a collision with a single pebble, or even a millimeter-sized grain, could cripple or destroy New Horizons,' says project scientist Hal Weaver. 'We need to steer clear of any debris zones around Pluto.' Researchers are making plans to avoid these hazards if New Horizons needs to. 'We are now exploring nine other options, "bail-out trajectories,"' says principal investigator Alan Stern. New Horizon's current plan would take it about halfway between Pluto and the orbit of its largest moon, Charon. Four of the bail-out trajectories would still take the spacecraft between Pluto and Charon's orbit. The other alternatives would take New Horizons much further away from Pluto, past the orbits of its known moons. 'If you fly twice as far away, your camera does half as well; if it's 10 times as far, it does one-tenth as well,' says Stern. 'Still, half a loaf is better than no loaf. Sending New Horizons on a suicide mission does no one any good. We're very much of the mind to accomplish as much as we can, and not losing it all recklessly. Better to turn an A+ to an A- than get an F by overreaching.'"
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Beware the Rings of Pluto

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    • by 0racle (667029)
      Yes.
    • by jellomizer (103300) on Wednesday October 17, 2012 @12:27PM (#41683425)

      Having or not having a moon isn't part of the definition of a planet.

      "(a) is in orbit around the Sun,
      (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
      (c) has cleared the neighbourhood around its orbit." [http://en.wikipedia.org/wiki/Planet#2006_definition]

      Pluto meets A,B and not C.

      C is there to discredit large asteroids in the asteroid belt.

      • by GNious (953874)

        Its a war on planetoids!

      • by mcgrew (92797) * on Wednesday October 17, 2012 @02:18PM (#41684859) Homepage Journal

        "(a) is in orbit around the Sun,
        (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
        (c) has cleared the neighbourhood around its orbit." [http://en.wikipedia.org/wiki/Planet#2006_definition]

        Pluto meets A,B and not C.

        Neither has Jupiter. [wikipedia.org]

        • by c++0xFF (1758032) on Wednesday October 17, 2012 @03:48PM (#41686069)

          Trojans don't count in the same way that moons don't count. Basically, the definition of "cleared the neighborhood" means that anything left is dominated by the gravitational influence of the planet. Moons orbit the planet, Trojans orbit the Lagrange points.

          Another similar class of objects are those in orbital resonance with the planet. The Pluto/Neptune system, for example. Or Cruithne/Earth. The planet's gravity dominates in each case, so we're OK there.

          The term "cleared the neighborhood" is unfortunately misleading. And purposefully vague, I always thought. When does the neighborhood become cleared? There's a lot of asteroids in our near neighborhood (which result in rather significant accretion events, so to speak).

          • by khallow (566160)

            The term "cleared the neighborhood" is unfortunately misleading. And purposefully vague, I always thought. When does the neighborhood become cleared? There's a lot of asteroids in our near neighborhood (which result in rather significant accretion events, so to speak).

            It is rather odd that such a slipshod definition has been rationalized on scientific grounds. I'm leaning towards that it's retaliation for the long ago act of naming Pluto [wikipedia.org] in such a way that the planet's name contains the initials for the discoverers' former sponsor, Perceval Lowell [wikipedia.org]. I doubt any one takes seriously the claim that in the future school students might be forced to memorize the names of hundreds of planets, merely because potentially hundreds could be found which would fit the existing definit

      • by Anonymous Coward

        Neptune is not a planet either since it hasn't cleared Pluto's orbit.

    • by Picass0 (147474)

      There are over 100 larger asteroids that either have moons or orbit each other as binaries or companions.

      http://www.johnstonsarchive.net/astro/asteroidmoons.html [johnstonsarchive.net]

    • by trout007 (975317) on Wednesday October 17, 2012 @12:54PM (#41683769)

      The center of gravity of Pluto and Charon is not inside of Pluto's radius.

  • by Anne_Nonymous (313852) on Wednesday October 17, 2012 @12:19PM (#41683325) Homepage Journal

    Potentially perilous Pluto path? Perfectly petrifyingly perigee perturbation!

  • when I was young, only planets were allowed to have rings!
  • 1/r^2 (Score:4, Insightful)

    by Khashishi (775369) on Wednesday October 17, 2012 @12:23PM (#41683383) Journal

    I thought if you fly twice as far, your camera will work 1/4 as well, not 1/2.

    • by Baloroth (2370816)

      I'm not a photographer, but I think: 1/4th the light, but 1/2 in terms of resolution. Light can be adjusted for, resolution cannot (well, sort of, there are tricks, but you'd rather use those on a higher resolution image to get better virtual resolution anyways).

      • by Khashishi (775369)

        The brightness of a large object won't change, but the resolution will drop by a factor 2 in each direction, so a factor of 4. The magnitude of a small object (sub-pixel) will drop by a factor of 4.

        Light can only be adjusted down, not up. Well, you can integrate for longer, but then you lose temporal resolution, which could be a problem if you are moving.

      • by Revotron (1115029)
        In an optical sense, a camera works just like a flashlight. When you double the distance from a flashlight to a wall, you get four times the coverage on the wall even though the circle of light is twice its original diameter. A camera's viewing area works the same way - double the distance between a camera and an object and the object appears at half its original dimensions, but the surface area of the object in the frame is only a quarter of the surface area in the original image. You've got the same nu
      • by Dcnjoe60 (682885)

        I'm not a photographer, but I think: 1/4th the light, but 1/2 in terms of resolution. Light can be adjusted for, resolution cannot (well, sort of, there are tricks, but you'd rather use those on a higher resolution image to get better virtual resolution anyways).

        Your thought is correct in that 1/4th the light, but the resolution remains constant (pixels are pixels). On the other hand, if there is not enough light to illuminate those pixels, they won't detect anything. Doesn't matter whether it is high resolution or not. Without photons, there is no image.

        • Your thought is correct in that 1/4th the light, but the resolution remains constant (pixels are pixels).

          I think what was meant was "pixels per unit surface area of the object." Still, personally I'd refer to an image resized from, say, 100x100 to 50x50 as being half the resolution.

    • I thought if you fly twice as far, your camera will work 1/4 as well, not 1/2.

      He was talking to Kindergarteners, not Khashishis. :)

  • Outrage (Score:5, Funny)

    by Joehonkie (665142) on Wednesday October 17, 2012 @12:27PM (#41683435) Homepage
    Now even our spacecraft are getting bailouts!
  • Damn right. I hear they are pretty pissed about the whole "planet" thing.

  • I always thought I had to worry about the rings around Uranus!

  • Even Pluto is married this days. Maybe we should nuke the moon to have a respectable ring around our planet, won't be a signal of intelligent life here (at least, not intelligent enough) but at least will be noticed by eventual visitors from outside.
    • Nuking the Moon won't get anyone's attention, it'll just create more mess.

      The 3rd rock around this star draws attention because it has copious liquid water, free oxygen in its atmosphere, and has both artificially produced light and sub-atomic particles emitting from it's surface. That should be more than enough to get someone's attention, if they happen to fly by.

  • Crazy thought (Score:4, Insightful)

    by Nethemas the Great (909900) on Wednesday October 17, 2012 @01:14PM (#41684045)
    So since most of the cost in any given NASA science project is in the hardware research and engineering not the construction, neither launch nor operation side why they hell aren't they making use of economies of scale? Stop building only one of something (well technically two, the "on earth version" and the "mission" version). Spread the risk out by flying in multiples. It would be unfortunate if one of them hits a "pebble" but the science returned would be magnitudes better because they're able to take advantage of opportunities that wouldn't be possible due to risk aversion. Take it a step further and make use of the same hardware R&D for multiple missions. Engineer a few platforms that are robust, and reasonably customizable. Each platform with a particular type of mission in mind. Put a Curiosity on Europa, Titan, and/or Ariel. Get an MRO around Ganymede, etc.. You don't need 7 minutes of terror if the hardware you spent more than $2B developing has already been flown and proven on other missions. You wouldn't be (as) scared to death that Congress will cut your funds because you're making good, efficient use of the R&D money. "Yes senator, that $2B from Congress has given us a platform we've reused on 10 missions now."
    • by JTsyo (1338447)
      oops, misclicked mod
    • Actually JPL should send MSL (Curiosity) clones to other places on Mars such as Mawrth Vallis (especially here). Sending MSL to Europa would be problematical because of the RTG; what happens to it when the mission ends? Could it kill putative Europeans? If you sent it to Titan it would boil away a hole in the ice and disappear or sink in a lake.
    • by pavon (30274) on Wednesday October 17, 2012 @02:40PM (#41685167)

      You don't really get much improvement in per-unit cost by building 10 of something vs 2. The biggest factor in the cost even with just the first couple isn't the engineering but the testing and qualification. Most of that has to be repeated for every unit you build until you are creating enough to have confidence in the past performance and to fall back to statistical testing, or at least are building enough for automating that work to be economical. But you would need to be creating several dozen of them for that to kick in. Furthermore, construction is more expensive that you are allowing for at those low quantities since it's all is done by hand, by highly skilled labor. That won't drop by much until you get into mass-manufacturing quantities, hundreds at least.

      So you would get minor savings, and at the loss of a huge amount of science. There is a reason that each of these probes is wildly different, and that is because the have wildly varying requirements. There is no one-size fits all suite of sensors. They will want different spectral ranges, different optics setups (detailed, narrow FOV vs wide coverage), different transmitter requirements (Horizon has much farther to transmit than MRO), all of which drives different battery requirements.

      Finally, the point of science is to keep learning; to keep pushing things forward. You do that by sending probes with improved and/or different capabilities, not just more of the same. Sure we could have sent 3 more MERs (Spirit/Opportunity) for the cost of Curiosity, but we wouldn't have learned as much as Curiosity will be able to tell us.

  • From TFA:

    "RELATED: Are you scientifically literate? Take or quiz."

    I'll settle for just being literate.

  • 'If you fly twice as far away, your camera does half as well; if it's 10 times as far, it does one-tenth as well,' says Stern.

    I was always taught that with optics it is the square of the distance, so twice as far away is 1/4 as well and 10 times further is 100th as well. But then, maybe when the changed the science that said Pluto wasn't a planet, it changed the physics, too.

    • Technically speaking yes, but casually speaking an image that's 10"x10" is generally regarded as being the "twice the size" of 5"x5", so it's that kind of thinking they're going with.
      • by Dcnjoe60 (682885)

        Technically speaking yes, but casually speaking an image that's 10"x10" is generally regarded as being the "twice the size" of 5"x5", so it's that kind of thinking they're going with.

        But that is the point, it's not 1/2 the size, but 1/4 (you can fit 4 5x5's in a 10x10).

        • Yeah, and that's my point. TFA is going with the popular easy-to-understand way of explaining things, rather than the technically-correct-but-not-how-people-think-of-it way.
        • by cyn1c77 (928549)

          Technically speaking yes, but casually speaking an image that's 10"x10" is generally regarded as being the "twice the size" of 5"x5", so it's that kind of thinking they're going with.

          But that is the point, it's not 1/2 the size, but 1/4 (you can fit 4 5x5's in a 10x10).

          It's half the width and a quarter of the area. Size generally does not refer to area, but rather a length scale. Thus, the article is correct.

  • Send the craft on a close approach, count on likelihood it will get most of the closer-up pictures on approach first and then maybe get destroyed. so what if it is destroyed while leaving?

    • Because while Pluto's visit is an important part of the mission, it's not the only part of the mission. So ending at Pluto would kind of cut off all the other research into the Kuiper belt.

    • by Tablizer (95088)

      so what if it is destroyed while leaving?

      The problem is that it uses on-board storage to collect and save the data and images, and then relays it all back weeks after the encounter. If it gets destroyed during a ring-crossing, it won't get a chance to send info back.

      To save money, it doesn't have highly maneuverable instrument booms the way Voyager did. Instead the whole craft rotates each instrument into position, and the instruments take turns doing their thing (at least the highly-directional instrument

  • IANAA* but from a layman's perspective, I'd rather zoom in and see what we can of Pluto even if we're taking a chance on destruction, than increase the chance this is a half-and-half mission. (I don't want another major mission aimed at Pluto - there are other things to look at out there.)

    * Astrophysicist

  • The imager can see 12th magnitude stars. It has both high resolution and high sensitivity, but no moving parts. A decade ago it was state of the art stuff. But physics is still physics. At twice the radius, a pixel will get one fourth the light flux, so will need four times longer exposure. That means four times fewer images. However, doubling the CPA also means half the slew rate, so it may not be so bad.
    The original article: http://www.space.com/18087-pluto-moons-rings-risk-new-horizons.html [space.com]
    The craft
    • by blueg3 (192743)

      Actually, the light flux per pixel is constant with respect to distance. The total flux from the object decreases as 1/r^2, but the number of pixels taken up by the object on the sensor also decreases as 1/r^2, cancelling this out.

      You can try this out yourself: set a camera to manual exposure and take a picture of a brick at distances of 1 and 10 feet. Compare brightness of brick between photos. (Alternately, simply consider the apparent brightness different between a tree tens of feet away and trees a mile

  • For being demoted from its planet status. :P

  • I was part of the Huygens european team in the Cassini/Huygens mission to Titan.
    On the US Cassini orbiter, there was a microphone, which was turned on when Cassini went to flyby Saturn, passing in the clear between two rings.
    The craft had been reoriented at that moment to get the large high-gain antenna facing speed, so as to protect everything between, and because of this the key crossing moment happened without Earth contact --only afterwards was it due to reorient back to Earth and tell us whatever happe

  • Sorry, have I missed something about the camera they're using? Isn't every camera two-dimensional and subject to the inverse square law?

    'If you fly twice as far away, your camera does half as well; if it's 10 times as far, it does one-tenth as well,' says Stern

    Surely "twice as far away" = "a quarter as well", and "10 times as far" = "one-hundredth as well"...?

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