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Space Science

Galileo And Cassini Team Up 108

Posted by Hemos
from the getting-the-most-data dept.
Bearpaw writes, "Trying to squeeze the last possible bit of use out of Galileo, NASA may team it up with the Saturn-bound Cassini for a joint mission. " The two will be perform some joint observations of the Jupiter system, as well as doing separate missions on the Jupiter system, including Ganymede as well. Hats off to the folks behind Galileo, whose official mission ended in 1997, but has kept on going.
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Galileo And Cassini Team Up

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  • I'm glad their doing this! NASA is cool even though they've had some failures lately Do you have any idea how difficult it is to send a spacecraft to something that is millions of miles away? It's a miracle that anything reaches their destination, especially with the budget cuts NASA's been suffering... some people can't even hit the toilet while peeing and that's right in front of them...
  • I never really guessed but I guess it could be possible considering that Jupiter is almost a star in and of itself because of the massive volume of gas the is within it.

    Jupiter is star-like with respect to volume of gas, but isn't the radiation associated with a star the result of the nuclear reaction(s) within? Jupiter isn't supposed to light up until 2010, right? :)
  • Of course once you hit about an 1/8 c you'd run into relativistic problems that would make you severely uncomfortable.

    You'd be fine. Relativistic effects only have to do with relative velocities. As long as the acceleration is within tolerable limits, a juman would feel no effects of moving as close to the speed of light as you like. The universe around you would start to look strange at large fractions of c (more like 3/4 or 9/10 than 1/8).

  • In the movie, yes, Big Brother was orbiting Jupiter. In the book, it was standing on Saturn's moon [JI]apetus, and Dave dropped through the roof. I never really liked the movie, though. They never had Bowman actually say "My God, it's full of stars," just a lot of trippy blinking.

    I wonder what it would be like to watch that travel sequence while drunk? Has anyone here tried it?
  • as has been said in the earlier replies to this post, it would be possible to do such, but inefficient. the orbits these satellites trace around the planets and moons within the solar system plot the pull of gravity against relative velocity. an orbit returning probes sent to other planets would be similar in theory to the orbits that the voyager probes made when they traversed the solar system decades ago. the major difference, of course, is that it would result in the probe returning to earth. the orbits which result in a probe being flung out into the reaches of the cosmos is called a hyperbolic orbit, with the focus of the hyperbola being the center of the gravitational field it is working against. in order to maintain an orbit where the craft can go slow enough to take any worthy readings of ambient conditions, (photographs, radiation and magnetic filed readings, etc.) the craft would need to be outfitted with its own source of thrust, which alone makes it ridiculously inefficient even disregarding the fact that the technology is outdated. however, this story not only makes me feel that NASA has regained some face with Galileo's longevity, but it truly is an excellent plan to study the ionosphere of the largest planet in this solar system.
  • by Anonymous Coward
    As I recall, Voyager 2 (like it's sister craft Voyager 1) was only designed to explore Jupiter and Saturn.

    Due to some very smart guys (hey, they're rocket scientists, after all) and a convenient alignment of the planets, Voyager 2 was able to continue on past Saturn and go to Uranus and Neptune.

    And it's still functioning (in a limited capacity), assisting in the research of the outer solar system -- solar wind, trans-Pluto objects, etc.

    And so is pioneer 10.. which is even older.. tho that one is expected to run out of fuel for its small reactor soonish.
    A while ago I received an e-mail from an ex nasa employee. He left NASA because he could no longer stand the ineficiency of the organisation. Actually low cost projects such as the pathfinder and the 2 clumsy projects to mars that failed will in time be just as good a way to go as the pioneer and voyagers were in their times.
    The problem however is that low cost operations and big budget organisations as a combination usually work out badly, if only coz big budget organisations often have big problems taking low cost projects serious because of the simple fact that they do not require a big budget... and heh, big budget organisations only get to be big budget organisations by paying a lot of attention on spending money in order to try to get even bigger budgets.

    Don't get me wrong btw, NASA does very cool things, but as long as budget is something that can make people more important then others (ie, as long as it plays an important public role) NASA will also continue to have problems which really don't do justice to all the hard work and knowlage of many of its real workers.

    So what I am saying is..
    1. expect high tech and frontier exploring organisations to make failures every now and then.
    2. Don't ever make budget more important then research and results, if you do the thing will eventually become hugely expensive and inefficient.
    (strange as it sounds, the more important budgets become, the more expensive things will be)
    This all isn't any easier for NASA because they are half operating like a commercial venture, and half as a government sponsored research institute, that simply makes it impossible for them to create an organisation that matches their operations, because their operations are way to diverse and vaguely defined.

  • First of all, photons are gamma and electrons are beta-.

    But it's the heavier particles (like iron nuclei) that do the most damage. They tend to rip up the target more as they zip through. Neutrons are interesting because they can get 'captured' by the target atom, changing it into a different (possibly radioactive) isotope. Slow alpha aren't particularly dangerous because have very little penetration. Fast alphas on the other hand are nasty. Gammas aren't particularly bad because they tend not to hit anything as they pass by.

    Ryan
  • Any suggestions for non-RTG, non-solar power sources for these things? IANAE, but for a Mars lander maybe you could use solar collectors on an areosynchronous orbiter and transmit the power to the surface via microwaves. On the other hand, RTG's are inherently hazardous, but maybe the public will eventually get over their fear of one blowing up in the atmosphere once space launces become more routine and the next-generation reusable launch vehicles are on line...
  • Wonder if the two spacecraft will be able to get any stero photographs. Preferably Jupiter and a moon or two.

    Or will the differences in their respective distances from Juptier be too great? For good stereo, the two cameras should be "close" together w/ respect to the subject(s), and roughly the same distance away.
  • >Bowman is pretty much completely silent after he
    >kills off HAL...he's sorta stopped being entirely
    >human.
    Interesting, I never thought of it that way. It seems to explain a lot of the last part of the movie, now that I think about it. I think I'm going to go watch the movie again tonight...
  • It would never be really possible to re-use a space probe like Galileo:

    • First, fuel costs would be prohibitive. In order to get out to Jupiter, the probe has to have enough velocity to move to a larger solar orbit. When a probe is launched it often follows a pretty complex trajectory to gain speed by using "gravity assists" from other planets. Now, imagine having to do the exact opposite.
    • Second, by the time the spacecraft has traveled to the outer planets, it is pretty much shot. Exposure to energetic particles, micrometeorites, etc. have a cumulative effect. In addition, a lot of the spacecraft systems are actually fairly fragile. The plasma wave antenna on Galileo is actually made of nothing but "robust" aluminum foil! (not to mention the PW antenna failed two years ago...)

    If you want to re-use a spacecraft, you can always use the "duplicate" that is usually built. (This was actually done for the Cluster II mission. The first Cluster mission exploded over the ESA launchpad, so the backups were brought into service!)

  • They tend to have a very low thrust. They can have high delta-v. You just have to run them longer. You can get much more delta-v out of a pound of reaction matter run through an ion drive than out of a pound of fuel burned in a chemical rocket.


    You also need a good power source to run the thing off of, such as a nice little nuclear reactor.

  • Any suggestions for non-RTG, non-solar power sources for these things? IANAE, but for a Mars lander maybe you could use solar collectors on an areosynchronous orbiter and transmit the power to the surface via microwaves.

    That's an interesting concept, but you're still fighting the low solar constant at Mars' orbital distance. Also, you're requiring two spacecraft where one will really do, with the second carrying a large solar array, plus the added microwave power transfer hardware on both ends -- or three of them, if you've got a rover on the mission. And the lander would still have to use batteries for heating during the very cold martian nights (the thermal cycles alone caused much of the wear on Pathfinder, and rechargeable batteries wear out). I think it's probably doable, but not on a faster-cheaper (I still won't say "better") program.

    On the other hand, RTG's are inherently hazardous

    That's the issue that really bugs me -- RTG's aren't necessarily "inherently hazardous!" [nasa.gov] The Soviets have had a bad time with them, but the US hasn't. We did have one release its radioactives on a failed launch back in '64, but it was designed that way -- the RTG burned up in the upper atmosphere, as intended (IIRC, the idea was to keep the radioactives from reaching the surface... disperse them up high, and they tend to stay there). Subsequently we've changed philosophies on this, and all RTG's are designed to survive reentry and still retain all radioactives.

    We know this works, matter of fact; there've been two "tests" in real life since the new "total containment" policy went into effect. Apollo 13's Lunar Module (the one the crew lived in and used for the critical trajectory corrections, following the explosion in the Apollo Service Module) carried an RTG which powered one of the scientific packages they were going to leave on the moon; the LM reentered the atmosphere at something like 7 miles a second, but the RTG remained intact -- we've monitored the air and water around the Tonga Trench in the South Pacific, where it landed, and there has been no release of radioactives. Even more illustrative of the safety of good RTG's: in 1968, a meteorological satellite booster went bad and was destroyed by Range Safety. The two RTG's on the satellite spent five months on the ocean floor in the Santa Barbara Channel (it was a launch from Vandenberg, into polar orbit); they were recovered intact, and were recycled into other spacecraft!

    but maybe the public will eventually get over their fear of one blowing up in the atmosphere once space launces become more routine and the next-generation reusable launch vehicles are on line...

    They can't "blow up," so that fear is totally groundless. Nevertheless, I doubt the public will get over it: we used to use RTG's routinely, but don't anymore, because of the very vocal opposition of a few groups whose "science" is definitely questionable. Anti-"nuclear" sentiment is becoming so widespread that truly idiotic things happen -- like the medical use of Nuclear Magnetic Resonance imaging (where "nuclear" refers to the atomic nucleus; the technique uses spin coupling between the nucleus and the orbiting electron in hydrogen, and has absolutely nothing to do with radioactivity) being renamed "Magnetic Resonance Imaging," simply because people were frightened of a word. I don't know what these fears feed on -- maybe guilt over Hiroshima and Nagasaki -- but I do know that people are being deliberated manipulated. But I won't get into that rant... ;>

    I hope people do get over this: it's hard to do science in the outer solar system without nuclear power of some sort. Hell, it's hard enough to do it with nuclear power! Past Mars, solar is totally impractical; carrying fuel for things like fuel cells is impossible, given the limits of spacecraft weight and the very long mission times (many years just to get there... and I hope the spacecraft keep their habit of working long past the nominal end-of-mission).

    The Russians still use them, of course -- but they appear to care nothing about public opinion... say, maybe this was all a commie plot! =8-0

    ---

  • I'd love to see a giant space-elevator, or an asteroid mining mission, or pretty much anything else in the series :)

    --
  • If you could manage to get to a reasonable fraction of c, you'd get annihilated by atomic particles and photons (now THAT would be a unique experience).


    --
  • is that baked potato you put in
    the microwave during lunch still radioactive and exposing your stomach right now? no, of course not. basicly, same thing.

    Well, basicly wrong. In fact, as a grunt grad student in space physics at UCLA in the 1980s, I helped perform these exact calculations. My background was radiation physics and radiation saftey (having just come from the IAEC in Vienna.) The baked potato was bombarded by relatively narrow bands of microwave energy and in a very moderate magnetic field. The Galileo probe has been continuously bombarded by everything from gamma radiation on down. Since metal is a crystaline structure, the metal atoms themselves have been taking a radioactive bombardment which has (if memory serves correctly) altered nearly one out of every 100 atoms in the crystal. I forget the tensile strength depression but it does mean that a substantial portion of the metal itself is now radioactive. The magnetic fields which Galileo has encountered have a cumulative molecular shearing effect on all the components which has further polarized the entire spacecraft. The net result being further molecular instability and radioactivity. Finally, because the engineers knew that no one would be coming near the plutonium reactor at the end of a boom on the probe, they didn't really bother to shield it particularly well. The leaking radiation from that alone would make the entire probe radioactive this long after launch.
    If you're going to try and take the piss outta someone, learn your facts first. Oh and put that potato in a nuclear reactor and then a plasma bath and then eat it. You won't be around to send out more inane comments.
  • Prior to the Voyager missions, NASA had proposed a "Grand Tour" Project that was to take advantage of the planetary alignment. However Grand Tour was scrapped, although apparantly still haunting the dreams of NASA planners. The Grand Tour option was left in for Voyager 2, but only if mission planners didn't decide that a second look at Titan would be more important. The trajectory diffences between the two really diverged at Saturn. Voyager 2 continued along the plane of the ecliptic, whereas Voyager 1 was thrown almost vertically "up". Up being defined as in the same direction as the Sun's North Pole. (The Sun, like Jupiter has very little tilt in relation to the ecliptic.)
  • Hey! Don't forget Pioneer 10. He just got a new lease on life. Not to bad for our oldest semi-functioning space probe.
  • Thanks for the replies, George.
    1. I missed the note about still crashing Galileo. Thanks for pointing it out.
    2. Yes, they had bigger budgets, but they were coming up with a lot of the items from scratch. The more stuff builds on what came before, the more inexpensive it should be. Also, newer tech should be cheaper, better and faster. I guess that's why I'm a retro-computer fan, it may not be pretty, but it works more reliably.
    3. I really meant that more as a joke, but yes, it probably does not have CMa to allow it to slingshot. Also, yes, you can adjust orbit but you can't escape the gravity well without the DV. (I think you meant that).
    So, thanks for the intelligent reply, I appreciated it.
  • Cost is NOT the only factor involved and it's not the contractor's fault when NASA isn't sure what they want. It's really all the fault of, drum roll please..., The Feds. NASA is rushed into doing all of their projects over the last 5 years in order to show results and receive continued funding. This is why a project like Galileo is still flying and the Mars probes are, well, what ever they are doing now. If you want real results, show support for the space program so that they can plan things better and actualy know what they need before taking bids. Honestly, more money is being put into NASA so that they can launch Satalites to watch us than is being put in for the betterment of mankind. "They just need to get into orbit, not to mars."
    This about it, if we don't speak up for what we want from the government, then they'll either assume that we don't care, and they can do whatever, or worse, they'll think we actualy aprove of this crap. Speak up, you can never have to many votes in an election.

    -Earthman

  • Yes, it's very cool. How'd you like to go spelunking through those...? God knows what you'd find.....

    Rocks?

  • Don't forget that Galileo was initiated under Carter and set up under Reagan, two presidents who didn't believe in the PC cr*p that runs NASA under our current clown, I mean president. Johnson and Nixon didn't really like all the people at NASA but they valued results over conformity to rules of how society was supposed to work. Carter may have wanted to be liked but eventually turned to 'just get it done', Reagan didn't care except for results, Bush knew a little more about the process but enough to stay out of it. Clinton has politicized NASA just like the INS, the FBI and nearly every other government agency. And he wonders why he'll be considered one of the worst presidents of all time.
  • some people can't even hit the toilet while peeing and that's right in front of them...

    Sure, that's easy for you to say. Maybe you've uncovered the reason behind those famous $750 toilet seats....

    (it had to be said, honest, it did...)
  • Let me guess... Energizer Batteries, Right?


    Nathaniel P. Wilkerson
    NPS Internet Solutions, LLC
    www.npsis.com [npsis.com]
  • Quoting the Author's Note from Arthur C. Clarke's 2010: Odyssey Two, "Finally, there is the strange case of the 'Eye of Japetus'- Chapter 35 of 2001. Here I describe Astronaut David Bowman's discovery on the Saturnian moon of a curious feature, '...a brilliant white oval, about four hundred miles long and two hundred wide ... perfectly symmetrical ... and so sharp-edged that it almost looked ... painted on the face of the little moon.' As he came closer, Bowman convinced himself that 'the satellite was a huge empty eye staring back at him as he approached...' Later, he noticed 'the tiny black dot at the exact center' which turns out to be the monolith (or one of its avatars.) Well, when Voyager 1 transmitted the first photographs of Iapetus they did indeed disclose a large, clear-cut white oval with a tiny black dot at the center. Carl Sagan promptly sent me a print from the JPL with the cryptic annotation 'Thinking of you...' I do not know whether to be relieved or disappointed that Voyager 2 has left the matter open." Personally, im anxious to see if this black dot is a real feature, or if its merely a few missing bits like the images of the "face" on mars is. thought fellow slashdotters might get a kick out of reading that though, especially those who havent been religious about their Clarke recently.
  • Van Allen belts baby! Yup, the same things that grab charged particles and create the northern lights here on Earth. Jupiter's belts are correspondingly larger and therefore grab a greater number of energetic particles and guide them into a shell around the planet. I think anywhere within the first two Galilean satellites is a pretty dangersous place.
  • the way they used to.
  • Well, not everything gose right, some times, even LINUX:-).
  • If you follow the links, you come to some pretty cool photos of Io. For some reason the URL I copied from my browser window doesn't work, so you'll have to do the work yourself.

    Joe Bob says check them out (only if you have a fast connection).
  • Ion drives still need a source of electrical power, in fact you'd need a bigger power budget because of it. Also, you'd still need chemical fuel for maneuvering and positioning thrusters, and Galileo is running low on that.
  • Let's be fair here. The "granola mystics" as jamesec unfairly names them, aren't afraid (at least the educated ones which are more than you think) of Cassini becoming a mini nuke. Plutonium 238, while not fissionable is just as nasty to the biosphere as 239. The watchdogs do serve a purpose, if only to keep NASA honest about such things. A few decades back, a NASA contractor got pretty sloppy about a liquid oxygen tank that was dropped in manufacture. About 2 years later, the damage would blow out the side of the Apollo 13 service module.

    The space enthuisasts and the environmental groups should be allies more often then at odds. Both sides share fault in this, but in my opinion, the arrogance of the techheads has done most of the damage.
  • Well, I'd like to see some kind of "press" confirming your Voyager 1 story. Titan is still an enigma, and the probe in question didn't even enter orbit: it merely shot around Saturn.

    I had always heard that due to Voyager 1's trajectory and earlier launch, NASA could not achieve the same flight path that Voyager 2 took because the celestial mechanics were not right at the time.

    Online gaming for motivated, sportsmanlike players: www.steelmaelstrom.org [www.steelm...gtargettop].

  • Yeah, but humans didn't discover that one (unless you count the proto-ape-man with the bone).

    I did forget about the Jupiter/movie vs. Saturn/book distinction. I thought the movie actually scored points on that one, since it looked forward to 2010 (the sequel) when the monoliths turned Jupiter into a baby 2nd sun (not enough mass there to do so, in reality, but Jupiter has much more than Saturn). Or was it that they went to Saturn in the 2001 book, but then to Jupiter in 2010? I'm getting confused... it's been a while since I read the books (and the movies seem to stick with me more for some reason, probably the stunning visuals). Honestly though the whole 2001/2010/2061/3001 series has pretty few internal inconsistencies like that, particularly considering the long period over which Clarke wrote them. Howabout a 3001 movie?!

    #include "disclaim.h"
    "All the best people in life seem to like LINUX." - Steve Wozniak
  • Let's be fair here. The "granola mystics" as jamesec unfairly names them, aren't afraid (at least the educated ones which are more than you think) of Cassini becoming a mini nuke. ...

    You must not have been paying attention during the Cassini protests. Either they were repeating drivel verbatim or they were deliberately lying. I believe it was some of both. Take a look at: http://www.nonviolence.org/noflyby/intro.htm [nonviolence.org] which deliberately tries to confuse a peaceful science probe powered by RTGs with space nuclear weapons. It switched from being an anti-Cassini site to a "throw the probe away -- don't flyby Earth" site. Please peruse the careful mixture of facts and, to put it kindly, non-facts. Moreover, a couple people who claimed to be members of that organization engaged in flame wars in sci.space.policy, so they can't even claim that the inaccuracies were accidental. They were pointed out during the flame war.

    ... Plutonium 238, while not fissionable is just as nasty to the biosphere as 239. ...

    Actually, Pu-238 is worse in the short term than Pu-239. It's shorter half life (86.4yr vs. 24,390yr) means that a gram of 238 will emit more radiation than a gram of 239. However, its faster decay means it won't be around as long. This is an advantage. A stainless steel shell can contain 238 long enough for it to decay to harmless levels. Of course it is Pu-238 dioxide, an extremely insoluable ceramic, so there was no great danger in the first place, but every little bit helps.

    ... The watchdogs do serve a purpose, if only to keep NASA honest about such things. A few decades back, a NASA contractor got pretty sloppy about a liquid oxygen tank that was dropped in manufacture. About 2 years later, the damage would blow out the side of the Apollo 13 service module.

    Yes, watchdogs help to keep a bureaucracy on its toes, but only rational ones. Far too many of the Cassini protesters had not read the environmental impact report, nor the summary posted on the web. They hadn't bothered to familiarize themselves with the structure of the RTGs nor the precautions taken against contamination. As such, they came off as a bunch of zealots who were railing against the Eviiilll Plutonium(TM) in the probe. It literally looked like a bunch of religious fanatics spamming web news sites and Usenet.

    Maybe you think this is an unfair characterization. If so, please check with Deja News and other archives. I suspect you'll be as embarrassed by these people as I was. In any case, none of them could have helped to prevent a subtle failure like Apollo 13. They simply don't operate at that level of detail and aren't interested in trying.

    Now, it is entirely possible that your educated granola mystics were not deceived by the spin and were not opposed to Cassini's launch. Or, if they were opposed, then they had actual reasons for their position. If so, then I must ask: Why were they silent? Why let the yammerheads grab and hold the spotlight? How can they expect a movement to be taken seriously when all the public sees is a bunch of loony tunes?

    The space enthuisasts and the environmental groups should be allies more often then at odds. Both sides share fault in this, but in my opinion, the arrogance of the techheads has done most of the damage.

    I agree that this should be and again I disagree on allocating the blame. 8-) Yes, I want to move nearly all heavy industry into space. Let's start mining the asteroids for metal and close all strip mines; let's try a test-sized solar power satellite, etc. It's the people who don't work out the possible risks and rewards of a proposal but respond at a knee-jerk emotional level that are keeping us stuck in the hole we're in. And, the vast majority of those folks call themselves "environmentalists," generally without taking a single college course in biology, statistics, ecology, etc....
    --

  • Amen brother. NASA needs to bring its "older crowd" up to speed on "new technology" and see what they can do. Just imagine what they could do with "todays" technology versus "yesterdays" technology!
  • "Because Galileo has been exposed to a plutonium reactor for the entire length of it's mission and has flown through some of the most intense radiation fields ever experienced, the entire probe is highly radioactive and would be extremely poisonous." This is a common misconception of radioactivity, the gallileo probe WAS exposed to large amounts of radiation from jupiters magnetosphere but it is not radioactive itself (except for it's RTG's of course)! is that baked potato you put in the microwave during lunch still radioactive and exposing your stomach right now? no, of course not. basicly, same thing.
  • I was paying attention to the Cassini protests, and reading a couple of more serious books published on Cassini hazards as well. I'm a bit skeptical on the tests NASA's made about the RTG safety however, I'd read NASA's worse case scenario studys, the one's I read only covered launch as opposed to the Earth flyby scenario, which would have resulted in a considerably more dangerous scenario considering the high speed involved in the Earth flyby. While the Plutonium used does have a relatively short half life, we're still talking major short-term damage if enough was released over a populated area. I would have preferred the use of a larger booster, or perhaps grouped boosters put together in orbit over an Earth flyby, but we don't have the techniques down yet for that last option. Considering that NASA seems to be having major problems with the implementation of "faster, better, cheaper", I have considerably less confidence in letting them handled a nuclear powered probe than I had at the time of the Voyager program. I would certainly want adequate funding to make those quality checks that seemed to be skipped lately and hiring enough system controllers to reduce fatigue and have enough cross-checking at critical points.

    Also, the radicals do sometimes serve a purpose in any movement you can think of. They keep issues live and frequently win maneuvering room that can be used my the moderates. I don't take Usenet seriously, it generally only attracts the most loud and roudy on any topic. The only environment that might be worse would be AOL chat rooms. Consider also, that we only see what the media chooses or is directed to cover. Rational scientists debating the wisdom of a Cassini flyby don't draw in the ratings the way sign-banging radicals would.

    As to your other proposals. As long as a substantical population remains on Earth, you need substantial industry just for support and supply. Considering that the repair of a simple pressurised room involved lots of people over months of time, we simply don't have the technology or the capability of running huge factory style operations in space. And given the low efficiency involved, I have problems with the idea of sending gigawatts of microwaves through the atmosphere just to get megawatts on the ground. Space has an important place in mankind's future, but not the primary role that enthuiasts seem to envision.
  • by eries (71365) <slashdot-eric.sneakemail@com> on Friday March 10, 2000 @10:06AM (#1211541) Homepage
    Doh, and all this time us Star Trek suckers have assumed it would be the Voyager probe that would come back and threaten to destroy the earth. Whoops!

    Want to work at Transmeta? Hedgefund.net? Priceline?

  • I'm glad their doing this! NASA is cool even though they've had some failures lately. I can't wait until I get to visit Mars.
  • this is good news for the ridiculed NASA.

    this kind of joint project if sucessfull will be a note of "hey we can still do it!"

    the problem with buget and popular opinion is a terable toll on NASA.

    the world as a whole needs to get exited about space travel again. we sent men to the moon in a tin can and some of the items left there (ive heard) are still working.

    i guess we just cant build them like we used to.

    YAY NASA!

    (i want to book my vacation on the moon but they will not let me yet..)

    "this is my computer, there are many like it but this one is mine..." -AYP?

  • It's good that something is finally going right for NASA. After all the mars problems, I'm glad to see something goin good for em. They needed it.
  • Is is at all possible that perhaps a space probe could be positioned in such a way that perhaps when and if the power would be lost that the vehicle could return to earth gracefully? Then all you would have to do is retool it and launch it again. That would make for an interesting concept and allow for more data to be gathered much more cheaply.
  • by Eccles (932) on Friday March 10, 2000 @10:16AM (#1211546) Journal
    Trying to squeeze the last possible bit of use out of Galileo

    My first thought when I read this? "I hope they don't expect too much, he's been dead for several hundred years..."

  • by MAXOMENOS (9802) <maxomaiNO@SPAMgmail.com> on Friday March 10, 2000 @10:20AM (#1211547) Homepage

    With all the media attention on the failures of NASA, it's good to see NASA's great successes: Cassini, Galileo, Voyager, Pathfinder, Viking, and most of all Apollo. When people talk about cutting the NASA budget, we can point them to these; and when they ask, "Yeah, but what did it do to save the environment," you can ask them, "How much are you willing to pay for knowledge that isn't immediately useful?"

  • With all of NASA's rotten luck lately watch 'em crash into each other. Or just disappear...
    ____________________________________ ________
  • I thought that they were thinking of crashing Galileo so it wouldn't contaminate any of the moons (esp. Europa/Io).

    Yes, it's great to hear good news coming from NASA. I think that they should re-hire and un-retire the folks who churned out Voyager and Galileo for the next Mars probe. It seems the older crowd were more hands-on oriented and the newer guys more theory-oriented.

    Why not slingshot Galileo back to Mars? It's old, it's not the most technologically-advanced hunk of metal floating around, but by Gawd it works!

    BTW, great line from the poster about V-ger, gave me quite a chuckle.
  • by Bad Mojo (12210) on Friday March 10, 2000 @10:14AM (#1211550) Homepage
    Next time NASA crashes a probe, or blows up a rocket on a launch pad, remember Galileo. When NASA gets bad press because it keeps throwing money away, remember Galileo. When someone wonders why the government spends money on NASA, remember Galileo. And while we may not get Tang from Galileo, I know there's a kick ass group of guys who built an unstopable, juggernaught of a probe. I think they called her Galileo.

    What can I say, I have a soft spot for space exploration. Hehehe.


    Bad Mojo
  • So we can finally discover the 2nd monolith... (the first one's on the Moon).


    #include "disclaim.h"
    "All the best people in life seem to like LINUX." - Steve Wozniak
  • NASA is cool even though they've had some failures lately.

    You'd have some failures too if you were being mandated to take the lowest bid on equipment that is being sent off to alien environments. If NASA had just spent the extra money up front on the first Mars mission, we wouldn't be having the Martian problems.

    Back to the topic, though... It's awesome that NASA is getting extra use out of a probe that was supposed to be written off three years ago. Hopefully, this joint mission will help us in our endeavour to better understand our solar system (which should give us a better idea of how the gazillion other ones out there work, too).

    djx.
  • by acarlisle (96757) on Friday March 10, 2000 @10:24AM (#1211554)

    This one [cnn.com] is pretty cool.

    -ac
  • Almost every article I read about Galileo talks about how it's been exposed to alot of radiation.

    The spacecraft has already endured nearly three times the radiation it was designed to withstand, but repeated exposure to Jupiter's radiation has taken its toll.

    What I don't understand is - what can radiation really do to the Galileo? I know the radiation we deal with on Earth is a whole different story then open space radiation, or the radiation around Jupiter.

    I could see it cause a memory fault, or cause a bad computation with the CPU/chipsets somehow. But I know Galileo has got redundant memory/CPU that would detect errors and recompute. Worse case, it would knock itself into "Safe Mode"; reseting itself to a safe status.

    What kind of "real" damage could radiation do that would shorten the life of Galileo?

    Jeremy

  • Actually - we're pushing that now. Since the mission that took David Bowman, Frank Poole, Hal and the others out to Jupiter supposedly took 18 months to get there... so we would need to find that thing soon so that we can build the ship, teach Hal how to think and launch the mission in the next 3 months - minimum...

  • by waldeaux (109942) <donahue@skep[ ].com ['sis' in gap]> on Friday March 10, 2000 @11:14AM (#1211559)
    The poster notes that the Galileo mission is doing very well because it has been extended beyond the end of its program in 1997.

    /. readers might also be interested to know about the International Ultraviolet Explorer which was launched in (I think) 1978 for a two-year mission. It lasted nineteen years in orbit taking data until it was turned off (in other words, it didn't fail - the switch was thrown).

  • by Graymalkin (13732) on Friday March 10, 2000 @11:14AM (#1211560)
    Technically the ion-drive isn't "slow" it merely has a low delta-v. Because an ion-drive can accelerate for very long periods of time the only real velocity limitation is the amount of fuel you have (which tells you how long you could run the engine). If you had an ion drive of a spacecraft and kept a constant acceleration of 9.6 m/s after a while you'd approach c. I think the approximate time is a year but I don't remember and don't feel like recalculating it. Of course once you hit about an 1/8 c you'd run into relativistic problems that would make you severely uncomfortable.
  • some positive news for NASA. I've become tired of seeing negative press about NASA, people complain about things like they could do any better. Whenever I hear someone bad-mouthing NASA I point Galileo out to them, functioning well dispite being three years past it's operational parameters, same with the Pioneers and Voyagers. I'm really hoping Cassini will be a huge success so the Pluto project will perk some eyebrows and hopefully get launched.
  • While your idea sounds nice it's impratical. First, the technology is so old it's not worth reusing. I worked on PVO data back in the mid-eighties and was amazed how hard the programming was. The computer had less power than in most calculators. Galileo, for all of it's success, has basically an Apple II hooked to a car battery which downloads power from nuclear waste. It's value as a probe is only in where it is and has virtually nil outside of that. Second, the systems are designed for one way trips. Because Galileo has been exposed to a plutonium reactor for the entire length of it's mission and has flown through some of the most intense radiation fields ever experienced, the entire probe is highly radioactive and would be extremely poisonous. While space techs will work in bad conditions, I doubt OHSA would permit as toxic an object to be worked on anywhere in the US. Third, if we signal it to turn around it has to get away from Jupiter and then keep transmitting until it's in Earth orbit. Thus wasting a long time in which it could gather more data. A soft landing in Earth orbit is virtually impossible unless a bunch of mid course corrections could be made requiring probe-controller interaction.
  • It's not practical, and here's why. As someone else pointed out, you have two options if you want to do this:

    1) An earth-return trajectory. This doesn't make sense, because you only get one flyby look at your target, it's hard to get close, and you are going FAST.

    2) Break out of orbit, and go home. This doesn't work because the fuel cost is prohibitive. Not just hard. Impossible with chemical rockets (go to nuke rockets, and it's a different story altogether). It's relatively easy (in terms of energy/fuel) to capture into orbit. Getting out requires adding alot of deltaV, which you can't get from gravity assist (because you've been captured), so it has to come from burning fuel. Which had to be accelerated along with the rest of the craft to get to the target in the first place. Which requires a LOT more fuel. And getting into orbit is relatively easy, but it isn't free, so you pay another fuel penalty when you get there. And of course, this makes the craft heavier and harder (i.e. more expensive) to lift. Bottom line is, when your run the numbers, you can't do it with anything like a reasonable vehicle size/cost. Which is a damn shame, since it would be cool to have stuff like this hanging around in a museum. But if we want to do that, we're gonna have to develop the technology to go out there and get it. Which is a whole 'nother can of worms.

  • --So we can finally discover the 2nd monolith... ---(the first one's on the Moon).

    Should be the 3rd monolith. 1st was on earth (remember the monkeys). The 2nd was buried on the moon.

    The 3rd was _orbiting_ around Jupiter. Gonna need those probes to look around instead of down :)

    No cigar, no lady on his arm. Just a guy made of dots and lines. - TMBG

  • being that i am too poor to get magazine subscriptions and too lazy to read alot of technical stuff on the internet, i have no clue as to what this ion drive is. call me flamebait if you will, but if someone could email me a link to a description, or a description itself, id appreciate it. i THINK i have a vague idea of what it is, but im not sure im even thinking about the right thing, and that which i am thinking about is only a vague description given to me by someone with an accent that was very thick, so i couldnt quite make out all that he was saying. beldaeron@zdnetmail.com
  • basicly you ionize Xenon gas atoms(Xenon because they are very massive per atom) then accelerate them in an electrostatic field, (usually generated by current from solar panels) and shoot them out the back of the spacecraft at a few thousand miles an hour(creates a perty blue glow too!). the amount of thrust produced is miniscule (about the same amount of force a piece of paper exerts on a table @ 1G) but you are doing it efficiently, so if you run it for a decade or two you'll be flying along at a nice clip.
  • Yer welcome,

    As far as point 2, I think they're planning on losing a few probes, with the cheaper and more numerous philosophy.

    I recall reading a quote from the NASA directory saying that if they didn't lose at least one probe, they overengineered them and spent too much money.

    I wasn't sure about 3, some people are serious about bringing it back.

    George
  • Second, by the time the spacecraft has traveled to the outer planets, it is pretty much shot. Exposure to energetic particles, micrometeorites, etc. have a cumulative effect. In addition, a lot of the spacecraft systems are actually fairly fragile. The plasma wave antenna on Galileo is actually made of nothing but "robust" aluminum foil! (not to mention the PW antenna failed two years ago...)

    Actually, your reply above is an element in favour of attempting to plot a reacquisition of one of these probes. If we humans are to survive as a species, we'll eventually be spending a lot more time out there in space, and I don't mean low earth orbit. I imagine there are quite a few scientists who would just about kill to have a probe in their hands that had seen a decade or so in the vicinity of jupiter's radiation belt.

    Such a return mission would be fairly expensive even compared to the cost of probes like Cassini, and would have to be designed into the mission, not just as an afterthought. Many of the objections mentioned previously would have to be taken into account, though I think such a mission would have tangible scientific benefits. We can simulate and test materials all we want here on earth, but need the actual conditions to really get a feel for the environment IMO.

    I suspect such a thing will eventually be done. It probably won't happen anytime soon though as we're a bit short-sighted here on this planet.

  • oh. well, that makes sense then. thanks.
  • Hmmm.. I guess I can't imagine learning much more from a piece of exposed metal than you normally do using the onboard instruments. (Besides, even with the 'harsh' conditions, remember space is still fairly empty. Besides small meteorite impact, there would probably not be any physical "damage" to the spacecraft to study.)

    Unless, of course, the spacecraft returned with "Kilroy was Here" spraypainted on the side...

  • Bah. Don't think of the movie as an adaptation of the novel, because the movie works MUCH better as a standalone piece. And the "trippy blinking", as you say, is just perfect, with or without drugs. Presumably the reason why Kubrick dropped the "my god, it's full of stars" is because, although it's a decent tagline, it just doesn't really fit Bowman's character at that point of the story. Bowman is pretty much completely silent after he kills off HAL...he's sorta stopped being entirely human.
    --
    "HORSE."
  • Well, I wasn't entirely sure myself, so I did some research. This [nasa.gov] page has a good description of the mission.

    A quick summary of the points I found:

    1) The Voyagers were in fact designed only for Jupiter and Saturn due to funding problems.

    2) Despite this, the mission planners realized that the planetary alignments allowed for the four-planet route, and left the option open accordingly.

    3) Because of (1), the engineered lifetime of the Voyagers was only five years.

    4) Voyager 1 could not complete the tour of Uranus and Neptune because of its Titan flyby. However, this flyby was planned for at the beginning of the mission; Voyager 1 was never meant to visit the two outer gas giants, not even as a contingency plan.

    5) Voyager 2 was actually launched first!

    Hope that clears some things up. It did for me!
  • Would it be possible to design radiation resistant CPU's using the internet model? A cpu that can re-route instructions from one set of transistors to another set with equivalent functions on the fly to re-create the original CPU in a virtual sense? Sure it would be slow to begin with and would get slower with increasing damage but you would still retain the function. Perhaps a chip with thousands of copies of basis transistor sets working in parallel (would need parallel code written for it). These sets can be used simultaneously to achieve reasonable speed but the chip will keep running until there's only one basis set left even if it slows to Hz speed. When this happens NASA will hire boat loads of programmers whose job it to simplify the requests made on this chip to essential functions in the least demanding way possible to extend the useful life of the chip.

    I guess its a minature beowolf cluster. My main point is that with a parallel approach, the weaker and smaller the individual processor the better as far as radiation resistance is concerned.

    Disclaimer: I know shit about about what I just wrote. Just a little mental masturbation.
  • It's sad that there won't be much chance for future planetary missions to have extended missions like Galileo, and the Voyager probes before it (just to name a few).

    Mars Pathfinder is an excellent example: the lander and its passenger, the rover Sojourner, were both designed to use solar energy, despite the fact that sunlight at Mars' orbit has only half the energy density it has here, and the expectation that the solar cells would be covered by dust and end the mission prematurely. But solar power, even though it was marginal (at best) for the mission, was a political requirement. Galileo and the Voyager spacecraft carried radiothermal generators, which is a big part of why they could keep going.

    I think that the Pathfinder hardware might still be working, if NASA had been allowed to use RTG's on it... remember, the Viking landers (with RTG's) also far outlasted their design lifetime. But public opinion prevented that -- the Cassini mission might be the last one that we get to launch with RTG's, and there was a lot of pressure to stop that launch simply because of them.

    Enjoy it while it can still happen: Galileo and Cassini may be the last of their kind!

    ---

  • FWIW, stereo photos are routinely made with just one spacecraft. Just take two pictures at different times, and the relative motion of the spacecraft and the planet (or other object) between shots gives the stereo separation. There have been some good stereo photos of the asteroid Eros lately, done just this way.

    Of course, timing is everything...

    ---

  • by karb (66692) on Friday March 10, 2000 @10:30AM (#1211576)
    You'd have some failures too if you were being mandated to take the lowest bid on equipment that is being sent off to alien environments.

    Whoa, there! Since I work for the company who's fault it would be if it wasn't nasa's, I've kind of been paying attention. I've been led to believe that both of the problem's were actually nasa's fault, not the contractors.

    Poor communications both times, I think. Not that the nasa guys don't rock (smarter than me, at least), just don't run around blaming my employer for bad things it didn't do. There are enough bad things it has actually done. ;)

    And about the lowest bid thing -- I'm not sure what the actual rules are, but I think to some extent you take the best bid -- i.e. cost is a factor, but not the only one. Contractors don't just submit a cost to the gov., they submit a amazingly large document (a proposal) about how they plan to do everything.

  • What I don't understand is - what can radiation really do to the Galileo? I know the radiation we deal with on Earth is a whole different story then open space radiation, or the radiation around Jupiter.

    There's radiation around Jupiter? I never really guessed but I guess it could be possible considering that Jupiter is almost a star in and of itself because of the massive volume of gas the is within it.

  • An interesting idea, but wouldn't it be cheaper (and faster, considering it took Galileo ~6 years to get to Jupiter) to build a new one from scratch, using lessons learned?

    To retool it, they'd end up ripping out all the 1980s-era electronics. They'd also have to test the probe housing to ensure it could stand another voyage.

    Another question: was/is Galileo nuclear-powered? The treehuggers would have a coniption if it came into orbit.

    And how would you get it back down to Earth? Obviously there is no re-entry capability built in, so you'd have to rely on a shuttle mission. That's not cheap.

    All this, assuming Galileo could break out of Jupiter's gravity at this point, given its fuel reserves.

    Online gaming for motivated, sportsmanlike players: www.steelmaelstrom.org [www.steelm...gtargettop].

  • I thought that they were thinking of crashing Galileo so it wouldn't contaminate any of the moons (esp. Europa/Io).

    They still are, it's in the article.

    Yes, it's great to hear good news coming from NASA. I think that they should re-hire and un-retire the folks who churned out Voyager and Galileo for the next Mars probe. It seems the older crowd were more hands-on oriented and the newer guys more theory-oriented.

    Well, the fact that the older guys had 10 times as much money to spend on Galileo, Voyager and Viking probably has something to do with it too.

    Why not slingshot Galileo back to Mars? It's old, it's not the most technologically-advanced hunk of metal floating around, but by Gawd it works!

    It probably doesn't have enough reaction mass to get to Mars, once your delta-vee is gone, you can't change your orbit.

    George
  • It's certainly possible, but it takes away somewhat from the length of a mission. By parking a probe in orbit around a planet (like they did with Galileo) you can get years of use out of it. For a probe to come back to Earth, it would either have to slingshot back around the planet, which means it would only get one chance to look at everything, or it would have to have to have a more powerful rocket and plenty of fuel - something that could pull it out of orbit and send it back towards us.

    In the end, it's actually much more cost efficient to just throw the probes away.
  • As I recall, Voyager 2 (like it's sister craft Voyager 1) was only designed to explore Jupiter and Saturn.

    Due to some very smart guys (hey, they're rocket scientists, after all) and a convenient alignment of the planets, Voyager 2 was able to continue on past Saturn and go to Uranus and Neptune.

    And it's still functioning (in a limited capacity), assisting in the research of the outer solar system -- solar wind, trans-Pluto objects, etc.

    Online gaming for motivated, sportsmanlike players: www.steelmaelstrom.org [www.steelm...gtargettop].

  • by BranMan (29917) on Friday March 10, 2000 @10:36AM (#1211582)
    Dang clever these Earthings...

    I'm glad that someone at NASA thought of teaming up on observations. The results should be even more spectacular than NASA expects. When reviewing code, multiple reviewers going over the code at the same time produces an effect greater than the sum of their findings - stuff that one reviewer finds will spark a connection for another, and so on. They called it the "Phantom Reviewer" effect back when I was taught about formal reviews.

    The same thing will happen for NASA - each of the probes will be gathering data in different spectrum, from different angles, at the same time. They expect to gain a lot from this, but I think it will exceed their expectations many times over. Though, the results will take a couple of years to be seen (it takes a long time to crunch a lot of data). I'm looking forward to seeing what the atrophysicists (sp?) can deduce from it all. We could be in for a few big surprises.
  • Trying to reuse these probes would be a little like donating old trash 80 computers to schools to upgrade and teach children with. The distances involved in interplanetary travel are to great for it to be practical, since it takes so long to go to say jupiter or saturn and back. By the time the probe returned to earth technology would have advanced enough to make it cheaper to build a completely new probe.

    It would be nice to get some of these probes back, though just to study the prolonged effects of radiation and extremes on the components. And if nothing else it would be cool to go to a museum and look at THE probe that had been to jupiter and back.

  • I've seen ppl rag on Hemos for bad spelling and grammar, but this is the worst I've seen to date. Really, dude... don't you at least scan over it to make sure it at least resembles the english language? Or does this look ok to you?
  • Actually, both Voyagers were specifically designed to tour all four outer planets. The combination that allows such a trip occurs only once every few hundred years, so they felt they should take advantage of it. While transiting Saturn, the mission controllers became so interested in Titan and its dense atmosphere that they sacrificed Voyager 1's mission to the outer solar system so that they could get a closer look at it. They were both originally intended to visit all four, but because of the redundancy they had with two probes, they could get by with only one for the other two planets. It is still going far past its design lifetime, but it was designed to visit all of the planets it did, in fact, visit.
  • From an article [cnn.com] at CNN on Jupiter's radiation affecting the chance for like on Europa:
    Jupiter has the strongest magnetic field of any planet, Chyba says, more than 10 times stronger than Earth's. When protons, electrons and other particles from space get trapped in Jupiter's magnetosphere, they are accelerated to extremely high velocities.
  • NASA's great successes: Cassini, Galileo, Voyager, Pathfinder, Viking, and most of all Apollo.
    Don't forget about Pioneer 10 and 11 - Pioneer 10 is still alive and making itself useful [nasa.gov]! And I think NEAR [jhuapl.edu] will join the list soon.

    These are the things that occasionally make me proud to be human.

  • Cassini is nuclear-powered, Galileo is not

    No, if I recall correctly, both Galileo and Cassini use RTGs (Radioisotope Thermoelectric Generators) for power. For decade long missions to the outer planets they are the only real option.

    Whether RTGs are "nuclear" depends on your definition. They don't use nuclear fission but instead use the heat from the natural decay of Plutonium 238 (not the bomb isotope P-239) but that's a detail totally ignored most of the granola mystics.

    Ion drives are cool. We need more experiments like DS1. (Curiously, you'd want a honest-to-Cthulhu space fission reactor for an ion drive mission to the outer planets. Either that, or plan to do most of your thrust while in the inner solar system.)
    --

  • Just to be fair, I think I need to speak up.

    I believe that you unjustly blame the current President for the failure of NASA. If anybody is to be blamed, it should be the American people. As a whole (not just the scientific/computer community), NASA does not have as much support as say education or National Defense. Because of this NASA has had a shrinking budget since President Johnson's term in office. This decrease in budget lasted all the way through till two years ago. Fiscal Year 1999 (which started in October 1998) is the first year in 30 years (since FY 1968) where NASA's budget has not decreased.

    Also, the current administrator of NASA, Dan Goldin, has been the administrator since Spring of 1992, which was during President Bush's term in office.

    I don't mean to sound like a like I am defending President Clinton, but I don't think the problem lies there. Must people in the Space Industry tend to lay blame for NASA's failures on the feet of Mr. Goldin, who invented the "Faster, Cheaper, Better" plan. All the projects in the last few months that have failed (specifically, Mars Climate Orbiter and Mars Polar Lander) were built under the Faster,Cheaper, Better. The first project, Mars Pathfinder, was also FBC, but it was a very successful mission. But to be fair to Mr. Goldin, FCB was invented because of the loss of the Mars Observer (which cost $900 M) which was a typical science mission (and lost in 1993).

    We must use facts in defending (and sometimes blaming) NASA, not demagoguery.

  • if you want to crash and burn, it does seem that the old big budget projects actually exceeded and outperformed design specs by years in this case. Big budget projects are also more fun to work on from an engineering standpoint, much like having hot grits in my pants.
  • Very interesting, possibly water-shaped rocks.
  • The contrast between Galileo's success and the recent tragic failures of the Mars probes is striking, and informative. While NASA administrator Dan Goldin's "faster, cheaper, better" mantra played well for congress what it really meant was that deep space exploration was stretched even thinner than it had been. Galileo had an adequate budget, that allowed for actually checking out the spacecraft before launch. A budget big enough budget that enough quality ground control was available to make the recovery from the antenna fault possible

    The recent Mars missions had a third the staff for three times the probes compared to the last series of Mars probes (the immensely popular pathfinder.) Is it any wonder that drastically understaffed and underfunded projects experienced failures? They didn't even have enough money to install equipment to transmit telemetry that would have allowed NASA to determine what caused the Polar lander's failure.

    On a long duration mission millions of miles from home, redundancy is a critical issue. This takes at least a little bit of money. The only time that redundancy on individual probes can be discounted is when they are very simple and there are a lot of them. There have been proposals of this kind, largely ignored by NASA.

    If you want successful space probes, give NASA the resources it needs to do the job. And don't throw billions away on the space shuttle. If we wanted a private space industry, it would take one thing: the announcement that the government was taking bids on a SSTO, in quantity, and that excess vehicles could be used by private industry.

    You'd have to stand back to avoid being hit by an entire new industry. Like with aviation in the early part of this century, gov't can play a part by doing research and creating an initial need to be met by private industry. (Early military and mail service contracts.) Once its started- and the banks assured that the companies will make money- you're off and running. Airplanes were soon being produced for cargo and passengers, and now the airline industry is a multi-multi-billion/year industry.

    When NASA was NACA, it did this well. Nasa should go back to its roots, do great research, but leave business to business.

  • Is it just me, or do both of those pictures look like background images you could find on the Web?

    Trust no one.
  • Yes, it's very cool. How'd you like to go spelunking through those...?

    God knows what you'd find.....

    Online gaming for motivated, sportsmanlike players: www.steelmaelstrom.org [www.steelm...gtargettop].

  • What I don't understand is - what can radiation really do to the Galileo? I know the radiation we deal with on Earth is a whole different story then open space radiation, or the radiation around Jupiter.

    Well, when the Galileo probe would get mad, it get really big, and green, and go on a destructive rampage.

    You wouldn't like the Galileo probe when it got angry.

    George
  • Quite a bit of radiation around jupiter actually. It cranks out a whole lot of RF noise, mostly from static discharges between Jove and Io. NASA's got it pretty well documented, and Arthur Clarke used it as a plot device in 2010.
  • by Bob(TM) (104510) on Friday March 10, 2000 @10:59AM (#1211598)
    Just like human systems, electronic systems have total dose limitations, too.

    Imagine the actual mechanisms involved. An energetic charged particle impacts a chip like an extremely tiny bullet - it destroys things along the way. It may take a while for a radiation hardened device sustain enough damage to render it useless because of the scale. But, eventually, enough impacts will drill enough holes (as well as generate cascading particles) so as to change the structure and toast your device.

    (Incidentally, the more transistors you pack into a package and the smaller the transistors get, the shorter the lifetime in a radiation hostile environment. Particle "bullets" do more damage and have a greater probability of hitting something you need.)
  • Cassini is nuclear-powered, Galileo is not

    That said, you're correct that it would be more effort than it is worth to bring a probe back and reuse it.

    Personally, I'm a fan of the ion-drive. Slow, but has the potential to last much longer and do much more, without the nasty safety factors of nuclear power.

    Kean de Lacy
    http://home.san.rr.com/dlacey/ [rr.com]

  • by Don Sample (57699) on Friday March 10, 2000 @11:01AM (#1211600) Homepage
    Practically, no.

    It may be theoretically possible to make it so that some of these probes were on some sort of free return trajectory, but I doubt it. Especially for a totally unpowered probe. Managing that sort of thing requires constant fine adjustments in the probe's trajectory. Even if you did manage to get it back here you would still have to catch the thing as it came wizzing back past the Earth at a few miles per second. The shuttle couldn't do it, nor anything else NASA has ever built.

    Trying to build a probe capable of doing that sort of thing plus the stuff needed to catch it if it did manage to come back would multiply the cost of the program by a few orders of magnitude. Cheaper just to forget about it and launch another one.

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