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NASA Spacecraft Set to Shine Spotlight on Mercury

ScuttleMonkey posted more than 6 years ago | from the long-lead-time dept.

NASA 71

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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first post (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#21948158)

there is a spotlight on my first posting prowess.

hahahahhahaa

i am the greatest first poster in teh history of slashdot!

Re:first post (-1, Troll)

Anonymous Coward | more than 6 years ago | (#21948648)

i hope your whole family gets mugged and raped by negroes

Re:first post (1)

professional_troll (1178701) | more than 6 years ago | (#21952246)

So I take it your a nigger that wants to rape his 5 year old daughter?

Just think (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#21948192)

When Dr Paul wins, we'll never have to worry about our taxes being wasted on things like NASA ever again.

Re:Just think (0)

Anonymous Coward | more than 6 years ago | (#21954398)

Hmm.. as a gyno, the man made a nice living dealing with pussies and getting comfortable with assholes.

Looking at his supportards, that now makes all the sense in the world...

No, no, no...didn't they read the book? (2, Informative)

Sunburnt (890890) | more than 6 years ago | (#21948240)

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

Popular teen author Vonnegut (1)

spineboy (22918) | more than 6 years ago | (#21948302)

Sirens of Titan.

Must be weird living on a planet where the day (=159 Earth days) is longer than it's year (59 Earth days)

SLASHDOT SUX0RZ (-1, Troll)

Anonymous Coward | more than 6 years ago | (#21948264)

_0_
\''\
'=o='
.|!|
.| |
let it shine, let it shine, let it shine [goatse.ch]

but why? (0, Troll)

ILuvRamen (1026668) | more than 6 years ago | (#21948338)

Isn't the sun an awfully big flashlight that's already shining on it? I mean if it's closer to Earth it must be pretty damn bright there. Why not just wait until what you wanna look like is facing the sun...then look at it lol. A giant space flashlight seems like a waste of much needed power on a spacecraft when you've got the sun right there.

Re:but why? (0)

Anonymous Coward | more than 6 years ago | (#21948962)

Mercuries rotation is synchronized with its' orbit in such a fashion that the same portion always faces towards/away from the sun.

Re:but why? (0)

Anonymous Coward | more than 6 years ago | (#21949024)

I thought it was in a 3:2 ratio. The Moon is locked in a 1:1 ratio with the Earth, but I don't think Mercury has a 1:1 ratio with the Sun.

Re:but why? (0)

Anonymous Coward | more than 6 years ago | (#21950146)

Correct! Take a look at this [wikipedia.org] .

Re:but why? (1)

Foobar of Borg (690622) | more than 6 years ago | (#21950152)

Mercury's rotation is synchronized with it's orbit in such a fashion that the same portion always faces towards/away from the sun.
That's an old, but incorrect, notion that was later corrected. As a sister post pointed out, it is a 3:2 ratio.

Re:Refrence for Mecury day (3, Informative)

Technician (215283) | more than 6 years ago | (#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)."

COPS (1, Offtopic)

Anne_Nonymous (313852) | more than 6 years ago | (#21948412)

>> 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

Re:COPS (1)

davidsyes (765062) | more than 6 years ago | (#21948832)

Yeh, and they'll be scared shitless if there is a huge green Gei... umm, gecko waiting for them.

Images (1)

Kryptonian Jor-El (970056) | more than 6 years ago | (#21949614)

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 . . . (3, Informative)

StefanJ (88986) | more than 6 years ago | (#21948420)

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 . . . (5, Interesting)

Deadstick (535032) | more than 6 years ago | (#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 . . . (1)

Mantaar (1139339) | more than 6 years ago | (#21948902)

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 "falling" towards Jupiter or other objects in space that can exhibit gravitational force upon smaller satellites of the sun or themselves.

Or am I completely mistaken?

Re:Why so long . . . (1)

Deadstick (535032) | more than 6 years ago | (#21949784)

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 . . . (4, Informative)

evanbd (210358) | more than 6 years ago | (#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:Why so long . . . (3, Funny)

Anonymous Coward | more than 6 years ago | (#21949884)

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:Why so long . . . (0)

Anonymous Coward | more than 6 years ago | (#21950868)

Where in Hades name do you work??

Re:Why so long . . . (2, Funny)

Drooling Iguana (61479) | more than 6 years ago | (#21953650)

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

Re:Why so long . . . (0)

Anonymous Coward | more than 6 years ago | (#21954580)

Lemme guess... Best Buy?

Re:Why so long . . . (3, Funny)

mcmonkey (96054) | more than 6 years ago | (#21955098)

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?

Re:Why so long . . . (1)

bwcbwc (601780) | more than 6 years ago | (#21959698)

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)

Re:Why so long . . . (1)

evanbd (210358) | more than 6 years ago | (#21960012)

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 orbital velocity -- but that's just choosing low delta-v maneuvers to accomplish the goal. Even if you chose a high delta-v option (for example, to get there faster), you can still treat the delta-v as a scalar.

What it really amounts to is that the rocket equation [wikipedia.org] and your propulsion system together allow your vehicle to change velocity by a certain amount; that's your delta-v. The direction part of the vector quantity of a specific burn (as opposed to the overall system budget) comes from your orientation system, be it RCS or gyroscopes or something else.

Hopefully that was relatively coherent... For an example of delta-v calculations at work, see eg Hohmann transfer orbits [wikipedia.org] .

Re:Why so long . . . (1)

bwcbwc (601780) | more than 6 years ago | (#21980556)

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."

Re:Why so long . . . (1)

Deadstick (535032) | more than 6 years ago | (#21993546)

Well, true...it's more rigorous to say "posigrade" and "retrograde".

rj

Re:Why so long . . . (1)

evanbd (210358) | more than 6 years ago | (#21996002)

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.

Re:Why so long . . . (1)

MichaelSmith (789609) | more than 6 years ago | (#21952870)

Messenger would have been a golden opportunity to try a solar sail.

Re:Why so long . . . (1)

Ihlosi (895663) | more than 6 years ago | (#21953436)

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.

Not the first mission to Mercury (4, Informative)

cusco (717999) | more than 6 years ago | (#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:Not the first mission to Mercury (2, Insightful)

CheshireCatCO (185193) | more than 6 years ago | (#21955770)

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.)

Re:Why so long . . . (1)

CheshireCatCO (185193) | more than 6 years ago | (#21954266)

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. Shedding angular momentum is tricky business, but inverting the usual gravity assist geometry to ditch the excess angular momentum works. (Before MESSENGER, I had wondered a few times to myself whether you might ever want to do that. Maybe I should have patented it or something. :-)

JPL's page. (0, Interesting)

Anonymous Coward | more than 6 years ago | (#21948434)

Here is the actual JPL page [tinyurl.com] for the mission. It's updated every day.

Check the mission pics on the left side as there are some preliminary pics of mercury. They are still a bit blurry.

not JPL!! NSFW gay porn video link! (1, Informative)

mr_mischief (456295) | more than 6 years ago | (#21948904)

NSFW!

Scam redirect!

Gay male porn video link in parent!

Re:not JPL!! NSFW gay porn video link! (2, Funny)

Carnildo (712617) | more than 6 years ago | (#21948986)

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.

Re:not JPL!! NSFW gay porn video link! (1)

mr_mischief (456295) | more than 6 years ago | (#21949072)

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.

Re:not JPL!! NSFW gay porn video link! (1)

schnikies79 (788746) | more than 6 years ago | (#21949268)

Me too, unfortunately I clicked on this one.. :(

Looks like you did too.

Re:JPL's page. (0)

Anonymous Coward | more than 6 years ago | (#21951126)

Parent is a troll. But this video [youtube.com] on YouTube has some great footage from previous fly-bys of Mercury.

Re:JPL's page. (1)

mgabrys_sf (951552) | more than 6 years ago | (#21951256)

Why don't you just Rick Roll us you uncreative fuck? Can't wait till you - or anyone you love - comes down with cancer. I'll send a singing card and a pack of smokes.

oh, you meant the planet. (1)

User 956 (568564) | more than 6 years ago | (#21948468)

NASA Spacecraft Set to Shine Spotlight on Mercury

Hint: Mercury is shiny.

Of course they've never been seen. (4, Funny)

techno-vampire (666512) | more than 6 years ago | (#21948492)

"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.

Oblig Hedberg (4, Funny)

Adambomb (118938) | more than 6 years ago | (#21948720)

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:Oblig Hedberg (0, Offtopic)

mr_mischief (456295) | more than 6 years ago | (#21948954)

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 episode and forgot where I'd first heard it. It's possible that I'd heard it somewhere else first, but chances are I first heard it from Homer J. Simpson. It's really amazing the staying power of a one or two-line observational joke.

Re:Of course they've never been seen. (2, Informative)

Peter Lake (260100) | more than 6 years ago | (#21952194)

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 observations give us an idea what to expect to see in the blank areas. Here's a map [unmannedspaceflight.com] combined with radar observations. There are also various recent Earth-based optical observations [skyandtelescope.com] 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!

Re:Of course they've never been seen. (1)

mz001b (122709) | more than 6 years ago | (#21953356)

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 point Hubble toward it. So these really are going to be never before seen images. Not just new, crisper images of previously seen terrain.

Bright light! Bright light! (4, Funny)

PhxBlue (562201) | more than 6 years ago | (#21948622)

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.

Re:Bright light! Bright light! (1)

wizardforce (1005805) | more than 6 years ago | (#21948888)

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.

Re:Bright light! Bright light! (1)

CheshireCatCO (185193) | more than 6 years ago | (#21955708)

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? (2, Interesting)

PhotoGuy (189467) | more than 6 years ago | (#21948678)

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.

hmm... (1)

Tumbleweed (3706) | more than 6 years ago | (#21949210)

That's hot.

Orbital Mechanics FTW (1)

Purity Of Essence (1007601) | more than 6 years ago | (#21949696)

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:Orbital Mechanics FTW (2, Informative)

Nyeerrmm (940927) | more than 6 years ago | (#21950446)

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.

Re:Orbital Mechanics FTW (1)

_Hellfire_ (170113) | more than 6 years ago | (#21950452)

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 position, attitude (which I guess is relative since there's no "up" or "down" in space), and course?

Would you calibrate it off Earth's known position in space (is it known?) and go from there or could you go off the stars your computer can see and identify - and would they move enough (relative to your position) to give you an accurate speed and direction?

Any JPL/spaceflight engineers out there that can comment?

Re:Orbital Mechanics FTW (2, Interesting)

Nyeerrmm (940927) | more than 6 years ago | (#21950540)

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

Re:Orbital Mechanics FTW (1)

Ihlosi (895663) | more than 6 years ago | (#21951146)

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 stars your computer can see and identify - and would they move enough (relative to your position) to give you an accurate speed and direction?



You could probably use other objects of interest, not just stars - for example pulsars. Just like on the Voyager golden records.

a good question (1)

Quadraginta (902985) | more than 6 years ago | (#21957370)

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 attitude is no problem. However, what you also want to know in deep space is the translational distance of your coordinate origin from, e.g. that of your starting point, e.g. Earth. That's pretty important stuff! That is, it's not enough to know that galactic North is this way, and if you look over there you're looking at the Sun. You'd also want to know -- probably very much! -- how far away the Sun is in that direction. If nothing else, that's going to determine how long you accelerate and when you plan to start decelerating. Don't want to overshoot or undershoot, right? Probably pretty expensive, even if it doesn't leave you fuel-less and marooned in interstellar space...

Now if you go large distances, a few thousand light-years or so, then of course the pattern of stars will shift around you, and if you have a good 3D map of the galaxy, you can triangulate and determine where you are. This would be like ship navigation by triangulating on landmarks when you are close to shore.

But what if you don't? What if, as seems more likely, you go 5-10 light years? Over that distance, the pattern of stars is going to change very little, if at all, simply because stars are so bloody far apart on average. So how good is your triangulation navigation going to be? Especially if, as happens to be the case presently, our knowledge of the exact 3D location of nearby stars is a bit spotty. It would be like navigating at sea by trying to measure the changes in how the surface of the Moon looks from different positions, made worse by not having a terribly good map of the Moon's surface to begin with.

I suppose one answer is just inertial navigation. Your trajectory in deep space is likely to be affected only by your own self-acceleration (which you can measure very accurately) plus the gravity of your source and destination stars, which you hopefully have measured before you set out, plus the average gravity of the galaxy in your neighborhood, which is hopefully pretty constant. God help you if you pass too close to an uncharted brown dwarf, however, and it's worth noting that there are probably thousands of these "hidden reefs" still undetected in the Sun's immediate neighborhood.

Re:Orbital Mechanics FTW (1)

Tastecicles (1153671) | more than 6 years ago | (#21951812)

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 was just one second off. Those two spacecraft left Earth's orbit with about twenty ounces of propellant each. They've been flying for how long? I'll bet those canisters are half full, and there'll be some left long after the thermopiles have died.

Re:Orbital Mechanics FTW (0)

Anonymous Coward | more than 6 years ago | (#21952630)

They programmed a TI-89 and hit the "Graph" button.

ds

That's Easy! (1)

LanMan04 (790429) | more than 6 years ago | (#21954306)

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.

Re:That's Easy! (1)

niktemadur (793971) | more than 6 years ago | (#21959684)

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?

Re:That's Easy! (1)

LanMan04 (790429) | more than 6 years ago | (#21968226)

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.

Re:Orbital Mechanics FTW (1)

CheshireCatCO (185193) | more than 6 years ago | (#21954404)

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 with any such job, an element of instinct and lateral-thinking is always required, and they do it very well.

Re:Orbital Mechanics FTW (1)

wiredlogic (135348) | more than 6 years ago | (#21960928)

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.

Is that an Earth Year or Mercury Year? (1)

Isaac-1 (233099) | more than 6 years ago | (#21950246)

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.

Trail blazed by Mariner 10 (2, Informative)

Lincolnshire Poacher (1205798) | more than 6 years ago | (#21951670)

> 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]

Re:Trail blazed by Mariner 10 (1)

CheshireCatCO (185193) | more than 6 years ago | (#21954328)

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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