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NASA Space Science

NASA Spacecraft Set to Shine Spotlight on Mercury 71

Posted by ScuttleMonkey
from the long-lead-time dept.
coondoggie writes to tell us Network World is reporting that NASA will this month see the realization of a mission launched in 2004, sent to explore the planet Mercury. "MESSENGER, launched in 2004, is the first NASA mission sent to orbit Mercury, the planet closest to the sun. But on Jan. 14 it will pass close by the planet and use Mercury's gravity for a critical assist needed to keep the spacecraft on track for its ultimate orbit around the planet three years from now. Still, the spacecraft is also expected to throw back some never-before -seen images, NASA said. The flyby also will gather essential data for planning the overall mission. After flybys of Earth, Venus, and Mercury, it will start a year-long orbital study of Mercury in March 2011, NASA said. "
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NASA Spacecraft Set to Shine Spotlight on Mercury

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  • by Sunburnt (890890) on Monday January 07, 2008 @07:43PM (#21948240)
    They'll have to land and go inside the caves if they want to find the harmoniums.
  • COPS (Score:1, Offtopic)

    by Anne_Nonymous (313852)
    >> NASA Spacecraft Set to Shine Spotlight on Mercury

    Why does this make me think police helicopter?

    Bad boys bad boys
    Watcha gonna do, whatcha gonna do
    when they come for you
    • by davidsyes (765062)
      Yeh, and they'll be scared shitless if there is a huge green Gei... umm, gecko waiting for them.
    • Still, the spacecraft is also expected to throw back some never-before -seen images, NASA said.
      No, its going to throw back images we've already seen...
  • Why so long . . . (Score:4, Informative)

    by StefanJ (88986) on Monday January 07, 2008 @08:03PM (#21948420) Homepage Journal
    It's hinted at in the story, but the reason the probe is taking its sweet time to actually achieve an orbit is Mercury's high orbital velocity.

    It's pretty easy to get into an elliptical orbit which stretches from Earth's orbit around the Sun to Mercury's orbit around the sun. But getting into a circular orbit means matching Mercury's velocity, and doing so in a way that lets a "burn" be made to actually enter into an orbit around the planet. As I recall, you need a total velocity change of 40 kps to get into orbit around Mercury. That more than twice the change required to get into an orbit around Mars.

    It's pretty impressive that NASA figured out a way to do this with a gravity assist. A proposed European probe would have used an ion rocket to make the velocity change.
    • Re:Why so long . . . (Score:5, Interesting)

      by Deadstick (535032) on Monday January 07, 2008 @08:48PM (#21948788)
      It's hinted at in the story, but the reason the probe is taking its sweet time to actually achieve an orbit is Mercury's high orbital velocity.

      Well, actually, Mercury's low orbital velocity. It's more than Earth's, but when that elliptical transfer orbit reaches Mercury's orbit, the spacecraft is purely hauling ass. It actually takes a negative delta-V to match velocities.

      To reach a superior planet (one outside your own orbit) you initiate the transfer orbit with a positive delta-V, then circularize it with another positive delta-V when you get there. For an inferior planet (inside your orbit), substitute "negative" for "positive" in both places.

      rj

      • by Mantaar (1139339)
        Yeah, I figure this is just like potential energy on earth: when something falls towards earth, it gains velocity. When you throw it up you'll need to supply it with the velocity yourself.

        As in space there's no up and down you'll have to imagine the space craft "falling" towards the sun when traveling to the sun and thus gaining velocity it didn't have in the beginning. Reverse for traveling to Jupiter.

        Of course, like all analogies, this one contains mistakes as the probe could also gain velocity from "
        • by Deadstick (535032)
          It's certainly a complicated dynamics problem, but the velocity changes associated with moving from one planetary orbit to another are orders of magnitude bigger than anything the gravity of the planets themselves can deliver. If you have the fuel to get into and out of the transfer orbit, you can maneuver around the planets themselves with the leftovers.

          rj
      • Re:Why so long . . . (Score:5, Informative)

        by evanbd (210358) on Monday January 07, 2008 @09:11PM (#21948930)
        Well, delta-v is usually treated as a positive scalar value in orbital mechanics. The propellant needed to change your velocity by (say) 3 km/s is independent of whether you're speeding up, slowing down, or changing direction. So, while velocity is a vector quantity with direction and magnitude, delta-v is usually treated as a simple positive-valued scalar. (At least when the impulse comes from a high-thrust rocket engine; for very low thrust things like ion engines, or weird things like solar sails, the problem changes somewhat.)
        • Re: (Score:3, Funny)

          by Anonymous Coward
          I freaking LOVE slashdot comments like this. I'm a goddamn nerd and the only time I hear about orbital mechanics is here. At work it's a never ending stream of fart jokes and stories about people defecating, and shitting, and crapping their pants, and drinking and crapping their pants, or drinking and crapping on the shower curtains, or eating and crapping on tables. I kid you not.
          • Re: (Score:3, Funny)

            Just wait until the next time they send a probe to Uranus.
          • by mcmonkey (96054) on Tuesday January 08, 2008 @12:17PM (#21955098) Homepage

            I freaking LOVE slashdot comments like this. I'm a goddamn nerd and the only time I hear about orbital mechanics is here. At work it's a never ending stream of fart jokes and stories about people defecating, and shitting, and crapping their pants, and drinking and crapping their pants, or drinking and crapping on the shower curtains, or eating and crapping on tables. I kid you not.

            And as a NASA employee, can you give us an insider's take on the mission?

        • by bwcbwc (601780)
          Is it the magnitude of the delta-v that causes it to be able to be treated as a scalar, or the fact that the delta-v is typically applied directly along the vector of velocity? (i.e. the rockets are oriented in parallel with the velocity vector before firing)
          • by evanbd (210358)

            It's both, really. To be specific, it's the fact that you can point the rocket in whichever direction is most convenient -- whether that's along the current velocity vector or not. If you had limitations about what direction you could point it (perhaps a solar sail, perhaps because you didn't want to point a radioactive exhaust at a planet) the problem would get more complicated. In general, if you're optimizing your orbital changes for low delta-v required, you'll be burning either with or against your

            • by bwcbwc (601780)
              Thanks. About all I know about orbital mechanics I learned from "The Integral Trees":

              "Out to go back,
              back to go in,
              in to go forward,
              forward to go out."
        • by Deadstick (535032)
          Well, true...it's more rigorous to say "posigrade" and "retrograde".

          rj
          • by evanbd (210358)
            But you can do burns that are neither. Generally they wouldn't be minimum-delta-v trajectories, but the trajectory does require that amount of delta-v. The only obvious useful example I can think of is shifting the orbital plane.
      • Messenger would have been a golden opportunity to try a solar sail.
        • by Ihlosi (895663)
          Messenger would have been a golden opportunity to try a solar sail.



          You usually don't want to try new and untested propulsion methods on a half-a-billion-dollars science mission. You pick a cheaper mission that has testing the new propulsion method as one of its main objectives, while doing some science on the side, e.g. SMART-1.

    • by cusco (717999) <brian...bixby@@@gmail...com> on Tuesday January 08, 2008 @12:21AM (#21949986)
      This isn't the first mission to Mercury, just the first mission to ORBIT the planet. Mariner 10 swung by the planet several times.

      "http://www.jpl.nasa.gov/missions/past/mariner10.html"

      It was also the first mission to use a gravity assist. At the time of launch the rotation period of Mercury was unknown. By an amazing coincidence, every pass of the spacecraft photographed the SAME FACE of the planet, as its rotation period matched exactly the interval of Mariner 10's return.

      • Re: (Score:3, Insightful)

        by CheshireCatCO (185193)
        Actually, that's not entirely shocking: Mercury is in a 3:2 spin-orbit resonance, so if the spacecraft always hit the planet in essentially the same solar-system longitude, there's a fair chance that the geometry would be exactly the same. (One chance in four, I'd say.)
    • As noted already, no: the problem is that the s/c will be going too fast when it gets there. A better way to look at these problems is (specific) angular momentum (which is conserved between orbital maneuvers/close encounters). Angular momentum increases as you move away from the Sun (as sqrt(a)), so the spacecraft, with a larger semi-major axis (in order to reach beyond Mercury's orbit at aphelion) has too much angular momentum when it's near Mercury. That means it's going too fast when it arrives. She
  • NASA Spacecraft Set to Shine Spotlight on Mercury

    Hint: Mercury is shiny.
  • by techno-vampire (666512) on Monday January 07, 2008 @08:11PM (#21948492) Homepage
    "Still, the spacecraft is also expected to throw back some never-before -seen images, NASA said."


    Am I the only Slashdotter who looked at this and thought, "Of course they've never been seen, they haven't even been taken yet." Yes, yes, I know what they meant, but couldn't they have said what they meant instead of something dramatic but wrong?

    OK, folks, see if you can manage to mod me down with a -1 Pedant, now.

    • by Adambomb (118938) on Monday January 07, 2008 @08:40PM (#21948720) Journal
      Here's a picture of me when I was younger......

      ALL PICTURES OF YOU ARE OF YOU WHEN YOU WERE YOUNGER.

      Heres a picture of me when i'm older....

      You son of a bitch, where did you get that camera?

      Ah, how i wish Mitch [wikipedia.org] was still rambling.
      • Re: (Score:1, Offtopic)

        by mr_mischief (456295)
        Of course, most people don't think of a picture from yesterday as "when you were younger".

        Still, as Homer and I like to say, "It's funny because it's true".

        AAMOF, I'd been saying that for years and it became an ongoing joke with my wife and some of our friends. Then, my wife and I watched season two or three or so of The Simpsons on DVD, and I heard the exact wording with almost the same timing I usually used. We about fell over laughing. I guess I picked it up from the show during the original run of that
    • Re: (Score:2, Informative)

      by Peter Lake (260100)
      Well, their dramatic wording is very correct - only about 45% of Mercury's surface has been imaged in detail. This was done 33 years ago by Mariner 10. So over half of the map of Mercury is still blank. It's the biggest unimaged planetary area in our solar system! Next week Messenger will image some of these never-before -seen/imaged areas of the planet (about 30% of it IIRC).

      Here's a current map [nasa.gov] of Mercury.

      There has been some interesting Earth-based radar observations using Arecibo's radio telescope. These
    • by mz001b (122709)
      Am I the only Slashdotter who looked at this and thought, "Of course they've never been seen, they haven't even been taken yet." Yes, yes, I know what they meant, but couldn't they have said what they meant instead of something dramatic but wrong?

      They are never seen because the only other probe to fly by Mercury, Mariner 10, only mapped about 40-45% of Mercury. MESSENGER will see the parts that have never before been seen. Additionally, Mercury is always too close to the Sun (in angular separation) to poi

  • by PhxBlue (562201) on Monday January 07, 2008 @08:29PM (#21948622) Homepage Journal

    NASA Spacecraft Set to Shine Spotlight on Mercury

    I can't imagine they'd need any more light on Mercury, what with the sun just 36 million miles off and all.

    Nice alliteration, btw.

    • the side facing the sun is really lit up but the other side is not, on that side because there is no air, it would be complete and utter darkness save for the stars in the sky. you might want to bring a flashlight.
      • Luckily, you can still do radar mapping and other experiments on the unlit face. And, if you wait awhile, the planet will turn for you and you can image it then.
  • Shine a spotlight? (Score:3, Interesting)

    by PhotoGuy (189467) on Monday January 07, 2008 @08:35PM (#21948678) Homepage
    How many candlepower must that spotlight be? Nuclear powered? Would it really light things up much more than the sunlight?

    Poor choice of a metaphor in the heading; had me thinking there was some illumination involved.
  • That's hot.
  • Whenever I read something like:

    ...on Jan. 14 it will pass close by the planet and use Mercury's gravity for a critical assist needed to keep the spacecraft on track for its ultimate orbit around the planet three years from now.
    ... I'm dumbfounded. How do they design these complex trajectories?
    • Re: (Score:3, Informative)

      by Nyeerrmm (940927)
      Probably doing some rough calculations with spheres of influence, and then putting those rough trajectories into an optimization scheme, probably with a non-linear programming problems. Do this same method with a number of different schemes (direct Hohman transfer, Venus flyby, out to Mars and back) and see what gets you to Mercury orbit with as little fuel required and with minimal risk of accidentally smashing your spacecraft.

      While its impossible to calculate these trajectories exactly by hand, its easy
    • Indeed! I've always been fascinated by celestial navigation. I understand how you can use a multitude of landmarks (and stars) to figure out where you are on earth, but what about the vast emptiness of space?

      Here's a hypothetical for someone more knowledgable on the subject: if we had a spacecraft capable of faster than light travel (think Starship Trooper troop carriers or Alien quadrilogy mining ships) to actually go somewhere interesting in a few months or even years, how does one go about determining po
      • Re: (Score:3, Interesting)

        by Nyeerrmm (940927)
        Theres a lot of significant work in star trackers to do attitude orientation within the solar system, and I'd imagine that as we explore further outward, we'll make decent enough stellar maps that you could determine your orientation from those maps, and also that you could determine the position based on the variations from 'known' configurations. Its just a question of good models and fast computers. A more practical implementation, something that a friend of mine is working on in fact, is the ability t
      • by Ihlosi (895663)
        Here's a hypothetical for someone more knowledgable on the subject: if we had a spacecraft capable of faster than light travel (think Starship Trooper troop carriers or Alien quadrilogy mining ships)

        Hm, it's been a while since I watched the movies, but isn't space travel in the Alien series a long and tedious sub-light process that requires the crew to spend much of their time in cryosleep ?

        Would you calibrate it off Earth's known position in space (is it known?) and go from there or could you go off the

      • I think you have a good question. See, here on Earth when we go somewhere through a trackless waste -- e.g. we sail somewhere on a ship -- we can figure out where we are simply by knowing our orientation (attitude) with respect to the fixed stars, which we do with sextant and chronometer. Since we live on the surface of a sphere, attitude (e.g. latitude and longitude) is all we need to know to know where we are.

        In space, it's equally easy to figure your attitude from the fixed (i.e. distant) stars. So at
    • It all boils down to weight.

      Keeping the amount of propellant required to a minimum means you don't need a honking big booster to get it off the Earth's surface to begin with - to carry the thousands of tonnes of propellant to achieve a direct flight. It's just not practical. Then the fun begins. As an historical example, Voyagers I and II's trajectories were calculated to the millisecond and then shot off in the right initial direction for their encounters - as it happens, V2's 1989 encounter with Neptune w
    • Whenever I read something like:

      ...on Jan. 14 it will pass close by the planet and use Mercury's gravity for a critical assist needed to keep the spacecraft on track for its ultimate orbit around the planet three years from now.

      ... I'm dumbfounded. How do they design these complex trajectories?

      It's actually quite easy! All you need is spice [wikipedia.org]. A Mentat [wikipedia.org] or two may also come in handy.

      • It's actually quite easy! All you need is spice.

        I, for one, welcome our new bloated, spice-crammed, shadow-of-their-former-human-selves Guild Navigator overlords.

        A Mentat or two may also come in handy.

        Those are only good once they're on the ground.

        What about last year's Sunshine, with its' slingshot rendezvous with Mercury?
        • by LanMan04 (790429)

          What about last year's Sunshine, with its' slingshot rendezvous with Mercury?
          Wow, funny you should mention that. That scene actually made me tear up; it was one of the most beautiful things I've ever seen, and I can just imagine being there.

          *pours out some of his 40oz in mourning of childhood dreams of being an autronaut*

          The Underworld soundtrack helped a lot as well...what an absolutely amazing movie.
    • There exists a considerable body of literature on the topic of orbital mechanics for spacecraft trajectories, which helps a lot. The spacecraft navigation folks are taught huge tracts of this as students (and probably pick up tons more as needed on the job). Of course, computers are also heavily employed to test and optimize trajectories.

      However, from what I've seen (working on a NASA mission), a lot of how trajectories get discovered is pure skill and creativity on the parts of the navigation team. As w
      • One of their interesting planning tools is the porkchop plot [wikipedia.org]. They provide a simple graphical system to make a rough estimate of when to launch when you goal is to rendezvous with another planet at a specified time. In the old days NASA used to print these up into a catalog for the mission planners to reference throughout the year. Nowadays they are integrated into the computerized planning tools.
  • It makes a big difference as a Mercury year is 88 earth days, nearly half of that time it is our of site behind the sun.
  • > is the first NASA mission sent to orbit Mercury

    Well it may be the first to technically orbit Mercury, but
    Mariner 10 used a Solar orbit to swing-past Mercury three
    times.

    http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1973-085A [nasa.gov]

    It was also the first probe to use plentary gravity assistance,
    in this case Venus, to change course. La plus ca change...

    Imagery here:

    http://nssdc.gsfc.nasa.gov/imgcat/html/mission_page/MC_Mariner_10_page1.html [nasa.gov]
    • Right, but a flyby is far, far less valuable than an orbiter. Look at how much more we've learned from Galileo and Cassini about Jupiter and Saturn (respectively) than several flyby missions combined.

      In this case, the situation is even better: we've never imaged 55% of the surface of Mercury with any kind of resolution to speak of. (It's difficult to image from the ground, what with having to catch it near the horizon, and Mariner, due to a resonance, caught the same side of the planet all three times.)

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