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NASA Spacecraft Set to Shine Spotlight on Mercury

Posted by ScuttleMonkey on 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. "

19 of 71 comments (clear)

  1. No, no, no...didn't they read the book? by Sunburnt · · Score: 2, Informative

    They'll have to land and go inside the caves if they want to find the harmoniums.

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  2. Why so long . . . by StefanJ · · Score: 3, Informative

    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.

    1. Re:Why so long . . . by Deadstick · · Score: 5, Interesting
      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

    2. Re:Why so long . . . by evanbd · · Score: 4, Informative

      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.)

    3. Re:Why so long . . . by Anonymous Coward · · Score: 3, Funny

      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.

    4. Re:Why so long . . . by Drooling+Iguana · · Score: 2, Funny

      Just wait until the next time they send a probe to Uranus.

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    5. Re:Why so long . . . by mcmonkey · · Score: 3, Funny

      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?

  3. Of course they've never been seen. by techno-vampire · · Score: 4, Funny
    "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.

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    1. Re:Of course they've never been seen. by Peter+Lake · · Score: 2, Informative

      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 of Mercury.

      There has been some interesting Earth-based radar observations using Arecibo's radio telescope. These observations give us an idea what to expect to see in the blank areas. Here's a map combined with radar observations. There are also various recent Earth-based optical observations using lucky-imaging techniques, but the images lack detail for accurate mapping.

      So to be pedantic the Messenger will take detailed never-before-seen images of never-before-imaged-in-detail and never-before-imaged-at-all -areas of Mercury. In few weeks we'll get a new map of Mercury!

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  4. Bright light! Bright light! by PhxBlue · · Score: 4, Funny

    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.

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  5. Shine a spotlight? by PhotoGuy · · Score: 2, Interesting

    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.

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  6. Oblig Hedberg by Adambomb · · Score: 4, Funny

    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 was still rambling.

    --
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  7. Re:not JPL!! NSFW gay porn video link! by Carnildo · · Score: 2, Funny

    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.

    --
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  8. Not the first mission to Mercury by cusco · · Score: 4, Informative
    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.

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    1. Re:Not the first mission to Mercury by CheshireCatCO · · Score: 2, Insightful

      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.)

  9. Re:Refrence for Mecury day by Technician · · Score: 3, Informative

    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/

    "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)."

    --
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  10. Re:Orbital Mechanics FTW by Nyeerrmm · · Score: 2, 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 enough for a computer to do so, and if you can give a rough starting place, optimization techniques will find solution. Trade studies are done to find the best method overall, as in any other engineering practice.

    Hope that helps some... it sounds like a fun problem to work out.

  11. Re:Orbital Mechanics FTW by Nyeerrmm · · Score: 2, 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 to use star tracker data to determine the positions of the planets. Based on ephemeris data (the very refined data made available from JPL regarding the position of celestial bodies) its just a matter of calculation to determine both the position and the attitude of the spacecraft. Of course from what I know those calculations aren't the easiest things, clearly. - A lowly graduate student in Aerospace Engineering

  12. Trail blazed by Mariner 10 by Lincolnshire+Poacher · · Score: 2, Informative

    > 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

    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