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Space Science

New Horizons Probe's Images of Jupiter 86

Posted by kdawson
from the by-Jupiter dept.
SeaDour writes "The Pluto-bound New Horizons space probe, launched a little over a year ago, recently succeeded in passing through a narrow navigational keyhole by Jupiter. Using the gas giant's tremendous gravity, the craft now has a significant boost toward its final destination, shaving three years off the time it would otherwise spend en-route. As it passed through the Jovian system, the probe took some fantastic images of the neighborhood, including detailed observations of erupting volcanoes on Io, time-lapse photography of Jupiter's tumultuous atmosphere, and the faint ring system that was first discovered in Voyager photography. These new images prove the capabilities of the small probe, which is set to reach Pluto in 2015."
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New Horizons Probe's Images of Jupiter

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  • by absolutely (1074008) on Monday March 12, 2007 @09:03PM (#18325861)
    And as we all know, it is Jupiters orbital velocity that gives the spacecraft its speed boost, not Jupiter's gravitational field. See: here [wikipedia.org].
    • by CrazyJim1 (809850)
      It must be all that centrifical force :P
    • by Anonymous Coward on Monday March 12, 2007 @09:38PM (#18326199)
      You don't know what you are talking about, and the Wikipedia article is screwed up as well. The Wikipedia article claims that no momentum can be gained passing by a stationary massive object. I'll give a simple counterexample. Drill a bore straight through the diameter of the Earth. If you pull a vacuum in this theoretical bore and drop a spacecraft into it, it will exhibit simple harmonic motion. What is interesting is that the object will have the greatest absolute momentum at the center of the Earth. Now take a rocket and fire only towards the center of the planet when you pass outwards from the center--not inwards. If you do this long enough you will reach escape velocity and say bye bye to the planet. Do your math calculating the momentum and you will find that you have got more absolute momentum that just from the rocket alone.

      Why is this so? First, momentum is conserved, the extra momentum is in the Earth in the opposite direction. Second, you were able to amplify your momentum because you minimized the time that your spacecraft felt the strongest gravitational fields pulling it back towards the planet when you were heading outwards (by using your rocket). But you maximized the time that your spacecraft felt the strongest gravitational fields pulling you into the planet when you were heading inwards coasting (because your rockets only fire when you are heading outwards). Strictly speaking the Earth does not give a great example of how this would work since the highest gravity of the non-uniform density Earth is about 1000 miles under the surface (and is 0 at the core due to Gauss' Law). But it may be more obvious if you arbitrarily move the 'bore' or path of the spacecraft so that its closest approach to the Earth is 2000 km above the surface. In this case it is obvious that you would coast until you got to the closest approach to the Earth and then fire your rockets for a few minutes to minimize your time in the highest gravitational field.

      This is sort of what a flyby could do if it didn't use its rockets and the planet had a high orbital velocity. Due to the orbital velocity alone you could target your spacecraft so that the planet recedes minimizing your gravitational interaction on the flip side (which requires you to fly by close enough to change paths a little bit since no path change would not do anything even with a high speed massive object). Of course using rockets and this method together are better.
      • by inviolet (797804)

        You don't know what you are talking about, and the Wikipedia article is screwed up as well. The Wikipedia article claims that no momentum can be gained passing by a stationary massive object. I'll give a simple counterexample. Drill a bore straight through the diameter of the Earth. If you pull a vacuum in this theoretical bore and drop a spacecraft into it, it will exhibit simple harmonic motion. What is interesting is that the object will have the greatest absolute momentum at the center of the Earth. Now

        • by radtea (464814) on Monday March 12, 2007 @10:39PM (#18326737)
          This is for the same reason as you give: it spends less time being slowed on the way out because its speed was higher than when it was falling inward.

          Nope. Think about it in terms of potentials and you'll see why this is not correct. The rocket's loss in gravitational potential energy coming out of the hole is exactly equal to the gain it got going in. It doesn't matter how fast it was moving at the start: the potential changes are determined solely by the source configuration because gravity is a velocity-independent force.

          Remember: Newtonian energy change is equal to the integral of force over distance, not time.

          The GP is correct in that mass discharged by a rocket deep in a gravity well has an added benefit. In terms of energetics you can think of this as being due to the gain in energy you get as the expended fuel falls into the well that you don't have to pay back when the spacecraft comes out of it.

          But there it is also the case that the orbital velocity of the planet generally gives a larger effect, although of course it would be misleading and silly to claim that this is not due to the planet's gravity, because what else would be causing the interaction between the planet and the spacecraft? It is true that if the planet had no orbital velocity nothing very interesting would happen, but the same would be true if it had no gravity. Not that either condition is likely to pertain to real planets.
    • Um... what? IANAPhysicist, but it seems to me the link you provided explains exactly that the gravitational field is used in this maneuver. True that it is combined with the orbital velocity, but without the gravitational pull, you have nothing.

      Or were you suggesting the spacecraft was using a lasso?

      • Re: (Score:3, Informative)

        by camperdave (969942)
        Gravity is definitely involved, of course. However, it is just the "medium" through which the change in momentum is transferred. Jupiter's orbital momentum is reduced by the amount same amount as momentum gained by the satellite. Since momentum is a function of mass and velocity, and since neither the mass of Jupiter, nor of the probe is changed, the satellite's velocity boost comes at price of Jupiter's orbital velocity. So the original poster is correct.
    • Re:It's both, really (Score:5, Informative)

      by Bastian (66383) on Monday March 12, 2007 @11:15PM (#18327083)
      If Jupiter didn't exhibit a strong gravitational pull on the probe, it wouldn't be able to have a significant impact on the probe's orbital velocity.

      If Jupiter were not moving w/r/t the sun and the probe, the probe's velocity w/r/t the sun would be no greater after the flyby than before.

      The way I see it, both gravity and orbital velocity are necessary components of the gravitational slingshot, so it's fair to say that it's a combination of the two that give the spacecraft its speed boost.
      • by Tablizer (95088)
        Agreed. Let's just see a pebble, or even an asteroid, in the same orbit do the same thing.
    • Re: (Score:2, Funny)

      by absolutely (1074008)
      Crikey, i never said Jupiter's gravitaional field wasn't a factor. But it's the orbital velocity that gives the spacecraft the extra push. Of course Jupiter's gravitational field is necessary to pull the spacecraft along in the first place, as the Wikipedia article I linked to clearly states. Can't people read between the lines or do I have to spell out even the bleedin' obvious?
      • Can't people read between the lines or do I have to spell out even the bleedin' obvious?

        You must be new here.

      • by Tim C (15259)
        Can't people read between the lines or do I have to spell out even the bleedin' obvious?

        You're posting on a site full of techies, well known for their pedantry and exhaustive attention to detail*, and you're surprised that people are pulling you up because you didn't spell out exactly what's happening but left a little to interpretation?

        (* And yet so often unwilling to use correct grammar, punctuation and spelling, apparently believing that it doesn't matter; the irony is not lost on me...)
  • So... what do the scientists do while they're waiting for the darn thing to get there?

    A watched-probe never gets to pluto.
    • by QuantumG (50515) *
      Kinda makes you wonder right.. Unfortunately, the probe doesn't fly itself. It needs occassional course corrections and all that stuff is worked out on the ground. So how much money did it cost to pull staff off other projects and put em on this Jupiter diversion? Is it really economical to pop by just to pick up 3 years? It's not like there's a time to market here.
      • by Beryllium Sphere(tm) (193358) on Monday March 12, 2007 @09:45PM (#18326257) Homepage Journal
        Probe has a finite design life. Save three years, improve the chance it will work when it's needed.
      • Re:the waiting game? (Score:4, Informative)

        by David Jao (2759) <djao@dominia.org> on Tuesday March 13, 2007 @12:48AM (#18327953) Homepage

        So how much money did it cost to pull staff off other projects and put em on this Jupiter diversion? Is it really economical to pop by just to pick up 3 years? It's not like there's a time to market here.

        There is a deadline here, and the deadline is a natural one. Right now Pluto is near its perihelion, which means it is (just barely) warm enough to have an atmosphere. There are many many things you can learn scientifically from an atmosphere. However, if the space probe takes too long to arrive at Pluto, the atmosphere will be gone by the time it gets there. In that case, we'll have to wait a cool 200 years before Pluto comes around to perihelion again.

        Quoting space.com [space.com]:

        Scientists believe that as Pluto continues its 248-yearlong orbit around the sun, its tenuous atmosphere eventually will freeze and collapse to the surface. Pluto has been racing away from the sun since its closest approach in 1989 and scientists do not know how much time remains before Pluto's atmosphere collapses. Once that happens its atmosphere is not expected to re-emerge for about 200 years.

        "Some people think its 20 years off and some people think its five years off," said Stern. "No one really knows when Pluto's atmosphere will snow out and collapse."

  • No it does not run Linux.
    • Re: (Score:1, Funny)

      by Anonymous Coward
      Nope, but if it ran windows, it would have crashed into the sun on it's last maneuver...

      Which is good because if windows was installed, the photos taken would not be viewable after downloading them as the owners certificate would not match the original and the DRM would not allow viewing unless they called 1-800-MICROSOFT and obtained a new key...

      Problem is the license sticker is ON THE SPACECRAFT!

    • by Rashdot (845549)
      And the probe won't go near Uranus either.
  • by Kingrames (858416) on Monday March 12, 2007 @09:37PM (#18326185)
    Whoop-de-do, slingshotting around Jupiter. They could have shaved a lot more time off the trip by slingshotting around the sun. :)

    But that method is usually only reserved for Starfleet emergencies.
    • I only wish they were doing some sort of "counter-slingshot" manoeuvre once they got to Pluto so the probe could stick around and study the planet, instead of merely flying by and heading out of the solar system.
      • by RoboRay (735839)
        It's certainly possible to put a probe in orbit about Pluto, but to do so would require either: A) Travelling so slowly that it would take a decade or more longer for the probe to even GET to Pluto, or B) Carrying so much deceleration propellant that you would need a Saturn V (at least) to get the thing off the ground to begin with. Due to cost and time constraints, neither of those options were viable for this mission. But, maybe someday things will be different.
    • by trongey (21550)

      Whoop-de-do, slingshotting around Jupiter. They could have shaved a lot more time off the trip by slingshotting around the sun. :)

      But that method is usually only reserved for Starfleet emergencies.

      Oh yeah, like that would work. After the probe went back in time it would be sending back the pix of Pluto before it took them. For that kind of money nobody wants blank negatives. Duh.
  • by Sloppy (14984)

    I always thought of New Horizons as an outer system probe. But with all that lag time, I should have realized..

    (wait for it)

    ..it was Io-bound too!

  • I hope they have some or will have some.
    I was looking around the many NASA pages and discovered that there are a LOT of 3D stereoscopic images online from Mars, the new Solar STEREO twin satellites, etc.. I found so much stuff that I decided to order a professional grade pair of 3D glasses for viewing it.

    • by Tablizer (95088)
      I don't think Jupiter is that suitable for stereographs. From the probe's perspective, the atmospheric features are generally pretty flat. Look at those near the edge of the sunlight portion (sunset or sunrise): they barely show any relief. And, it didn't get close enough to the moons to really see mountains and craters in stereo, at least not dramatically. It generally takes a close, slow pass for good geography stereography.

      Plus, the atmosphere of jupiter would probably move between frames to mess up visu
      • In fact they often use deep depleted CCD's for those lovely images. Broad spectral response from deep IR *(not heat) through UV. Slice in 5 filters and you cover a lot of ground optically.
        -nB
  • The probe is already so popular that they formed a religion around it [nhmin.org].

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