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NASA Spacecraft Set to Shine Spotlight on Mercury

Posted by ScuttleMonkey on Mon Jan 07, 2008 07:30 PM
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. "
+ -
story

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[+] Messenger Flies by Mercury 170 comments
Riding with Robots writes "Today, more than three decades after the last spacecraft visited Mercury, Messenger buzzed just 200 kilometers above the planet's surface. During the encounter, the robotic spacecraft conducted a range of scientific observations, including imaging swaths of Mercury's surface that have never been seen up close before. A few of the first pictures are now available, with many more to come in the next few days."
[+] Messenger Probe Sends Back Mercury Photos 137 comments
arbitraryaardvark writes "NASA's Messenger probe flew past Mercury at a distance of 125 miles. The spacecraft took hundreds of pictures during the pass, updating photos from the now 30-year-old Mariner mission. According to an article at the International Business Times, the probe will eventually settle into orbit around Mercury in 2011. 'The images obtained by the $446 million MESSENGER mission (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) this week contain some of those unexplored areas. One image released Saturday was taken after Messenger made its closest approach to Mercury last week. In the photos released this week, scientists have observed unexplored cratered areas of the planet. On Monday, Messenger made its closest approach to Mercury yet, aiming for new discoveries. Among its goals is to discover if Mercury has ice water in its polar craters and to complete the mapping of the whole planet.' Meanwhile here on Earth, a joint EU/Japan probe with an ion drive is set to head towards Mercury sometime in 2013."
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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.
  • 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

      • 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.
          • 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 cusco (717999) <brian.bixby@gm a i l.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.

      • 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.)
  • 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.
  • 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.
  • 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)

      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
      • Re: (Score:3, Interesting)

        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
    • NSFW!

      Scam redirect!

      Gay male porn video link in parent!

      • You know, there's a reason why most of us don't trust URL redirector links posted on Slashdot. Still, I'm disappointed. The traditional target for these links is Goatse.
        • I don't trust them either, but I'm often curious and nobody's going to fire me for opening them on this system. It sometimes entertains me to see what the trolls are linking and if I can help keep someone from losing a job by clicking absentmindedly, I think it's all worth it.
      • by Technician (215283) on Tuesday January 08 2008, @02:06AM (#21950428)
        Mercuries rotation is synchronized with its' orbit in such a fashion that the same portion always faces towards/away from the sun.

        http://www.enchantedlearning.com/subjects/astronomy/planets/mercury/ [enchantedlearning.com]

        "Until 1962 it was thought that Mercury's "day" was the same length as its "year" so as to keep that same face to the Sun much as the Moon does to the Earth. But this was shown to be false in 1965 by doppler radar observations. It is now known that Mercury rotates three times in two of its years. Mercury is the only body in the solar system known to have an orbital/rotational resonance with a ratio other than 1:1 (though many have no resonances at all)."