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Space

Cassini Greets Jupiter 94

Posted by jamie from the can-I-borrow-a-cup-of-potential-energy dept.
Dr. Zowie writes "The Cassini probe, despite predictions of doom on launch and on its Earth flyby, appears to be working just fine as it wends its way outward toward Saturn. It's currently flying by Jupiter for an additional gravity assist. Today, the imaging team released their first high ('better than Hubble') resolution color images of Jupiter. I can't wait to write a Jovian screensaver..." Halfway down that last page is a sweet movie (GIF or QT) showing time-lapse clouds around the Great Red Spot on successive rotations of our largest planet.
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Cassini Greets Jupiter More

Cassini Greets Jupiter

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  • 99 Sites on the Web (Score:4)

    by superdoo ( 13097 ) on Monday December 04, 2000 @12:02PM (#582572) Homepage
    99 sites of stuff on the web,
    99 sites on the web,
    Slashdot one down,
    into the ground,
    98 sites of stuff on the web.

  • Please will someone who opposed the launch of the Cassini probe please reply to this message? I have something very urgent to say to you....

    HA HA. U R DUM.
  • Hubble's great-- but there's really no substitute for a flyby. The Voyager probes produced better pictures than Hubble, (as did, I suspect, some of the Pioneer probes). And then there was Galileo...
  • Hubble cannot take a picture of the Earth, Moon or Sun. Everything else is fair game... assuming no comets or large bodies come extremely close to it.
  • You may have noticed that hubble photos often have the acronym WF/PC2 somewhere in them? This stands for Wide Field/Planetary Camera 2 (#1 being the one they replaced in the 1st servicing mission to fix the optics). Anyway, the Wide Field part is a wide angle camera for taking pictures of deep space things like the Lagoon Nebula and the Planetary Camera part is a high-power camera for taking pix of planets. The only thing that could be "too bright" would be the Sun, which would damage the CCD. For other things, if they are bright they would just make a shorter exposure. However it *is* pretty dumb to compare photos taken from a camera right on the Jovian doorstep to ones taken from Earth. That's like comparing HST photos of Mars with ones from the Mars Orbiter.
  • not to mention tornados :)

    When I lived in colorado, we used to visit denver right after a big storm and look at all the wreckage produced by a tornado. A lot of times you find foundation where buildings are supposed to be.. cars upside over... etc etc.

  • The joke would be funnier if it took into account that it's Earth's gravity that is reduced by the launch of Cassini (in direct proportion to the combined mass of probe, fuel expended, etc.), not that of any other extraterrestrial object. What Cassini is stealing from other objects is angular momentum. As it slingshots around various objects, the energy it derives is converted from planetary inertia to probe speed.

    Hence, if we continue launching probes and using other planets to slingshot them up to escape speed, Venus (and other planets) will eventually spiral into Sol as Earth spirals outward toward Pluto.

  • Na, it was this book "Coal Powered Space Craft for Dummies" They got the units all messed up; newton-meters, foot-pounds, cubic-zirconias, ...

    What with Morton Thiocol rubber bands snapping and all that powdered magnesium on board for flash photography, that's the last time I'm talked out of using fulminate of mercury as the propellant!

    --

  • ... particularly the images of Saturn, and the Red Spot on Jupiter. Gorgeous stuff, and definitely in our Solar System. Here's a link to the Heritage Project [stsci.edu].

  • Why did they blast a cassino to Saturn?

    Is it profitable?
    Just kidding :)
    BTW, nice pictures!
  • (3) determine the nature and origin of the dark material on Iapetus' leading hemisphere;

    Personally, I want to know the nature and origin of that large black monolith on the other hemisphere...
  • I remember the Cassini protests outside the whitehouse (from CNN). Some dude carrying around a poster "Our Last Sacred Space" with a drawing of an alien like on the X-Files. Like he thought we were polluting Saturn or something...
  • Another protest page [aol.com] on Space Debris makes good points and very, very bad points. It calls probes like Cassinni and the Voyagers "Space Debris" that with no way to make it back to earth become interplanetary garbage.

    The point about useless satellites in Earth orbit is far more sensible until the author suggests that advanced civilizations might use "miniature black holes" to clean them up. If you thought running an RTG close to the Earth was bad, imagine containing a black hole in the Earth's orbit (or rather, the Earth in orbit of the black hole!).

  • When will NASA learn that the entire *purpose* of putting these images up on the internet is so people can make the pictures into desktop backgrounds? You call these high res? I want my 1280x1024, dammit.

    --

  • Lets put it this way: the only danger involved with Cassini was likely generated by the media, who heard "nuclear material" and "launched into space", saw a ratings-garunteed story, and ran with it. As has been pointed out before, the level of radioactives was really quite low - as was the danger. Radioactives are a natural part of nature... one that just happens to be dangerous to humans in large quantities.


    -RickHunter
  • looks like the OSU httpd server they are using on their VMS/VAX machine is not holding up to slashdotting.. big iron is getting old.. I remember running batches on the VMS/VAX machines at the U of A. used to think they were cool.
  • I doubt anybody on Slashdot is into astrology, but a few of you must have heard the Orb track "S.A.L.T.". It featured a Scottish fundamentalist preacher talking about the apocalypse, and said that the planets would be aligning on August 18th, 1999, which would signify TEOTWAWKI. That was exactly one day after the Cassini flyby. Way to add to my irrational fear.
  • It's not a vax, it's a 600MHz Alpha.
  • Damn, I've been anti-nukes since long before it became politically correct to be it.

    It's a very unfortunate fact that now that everybody is anti-nukes, you can say anything and get away with it. I hate that, it undermines the efforts of knowledgeable anti-nuke and anti-war advocates. Cassini was never an issue, none of the three concerns you list were valid, as is very apparent if you sit down and do the math yourself.

  • I once did a back-of-an-envelope calculation, and got to about 100 deaths myself as a worst case scenario, using the standard linear model. It's well known and you can find it in any biophysics text book. These calculations are very easy.

    However, there is mounting evidence that the standard linear model is wrong, that small doses of radition isn't dangerous, and I would be surprised, very surprised if a reentry where the RTGs dissolved, which is the worst-case scenario, pretty much, caused any deaths at all.

    Finally, you might want to read Carl Sagan's article about the launch of Galileo [dartmouth.edu]. It was the same issue back then, and as good as every point he made back then is valid for Cassini, and indeed similar future projects.

  • So... Who's idea was it to give mental patients internet access?
    Come here George and let the nice man in the white coat give you your medication...


    Hacker: A criminal who breaks into computer systems
  • Well you would get squashed b4 you'd notice wouldn't you? ;-)

    Wasn't there this weirdo theory a while ago that the very inner core of jupiter might be a giant (earthsized) diamond?
  • hmmm, imagine to pass over from the calm bit into the storm... talk about rollercoaster...
    mind you, is it a sharp edge between the storm and other areas or is there a slow transition between them?
  • Hey! They Found Ripley's Escape pod in ALien 2, though!!

  • dunno about the states, bu tyou don't need to 'register' it over here europe... Also you can use a pair of binoculars to look at Jupiter
    Jesus.... Why would the gov make up something like this?? No purpose in doing so.... get a life....
  • > Frankly, I would think that the author of that
    > website would be happy to have something that
    > was dangerous and already here to be shipped
    > out into eternity.
    Negative. The Plutonium was not already here. Plutonium has a rather short half-life (100 years?) which means that any naturally occurring Plutonium which was created along with the Earth is long long gone.

    All the Plutonium we play with is transmuted from Uranium in atomic reactors.

  • who wants to go with me to get it ;)
    hahaha

    .ph0x

  • Chicken Little's Anti-Cassini website (Score:3)

    by rebill ( 87977 ) on Monday December 04, 2000 @12:06PM (#582599) Journal

    I checked out that anti-Cassini website under the predictions of doom link, and found that the author's primary complaint was that the 74 pounts of Plutonium might crash into the Earth. Maybe over Africa.

    Let's see. Africa has 6,900,000 square miles or so. Seventy-four pounds of plutonium is about 34,000 grams. Assuming that Cassini broke up and only affected a third of Africa (2.3 million square miles), that's 0.014 grams of plutonium per square mile.

    Frankly, I would think that the author of that website would be happy to have something that was dangerous and already here to be shipped out into eternity.

    Some people just don't think.

  • While I realize I'm feeding a troll here, I just wanted to mention to him that he could go out, pay $500 for a good reflecting telescope and point it at Jupiter. If you are able to focus it correctly, you will get an amazing (but small compared to Cassini's) images of that planet that doesn't exist! Try it, it works! :-)
  • Even if we assume that none of the cancers forecasted has arisen (and that's an absurd assumption to make, since cancers take decades to appear in exposed populations)

    Apparently, you did not read your own source:

    an accidental re-entry of the spacecraft into Earth's atmosphere

    There was NO accidental re-entry, therefore there will be NO exposed populations for the cancer to appear in. Ergo, it is NOT an absurd assumption.

    And to address your concern over the cancer risks should the probe have crashed, it may have caused no cancers at all as well. There is a whole branch of science devoted to communicating risk. It is by no means perfect. The major question is: How did Dr. Burden arrive at his numbers?

    If Dr. Burden assumed the world population as the exposure group then: 3,480 / ~ 6,000,000,000 = 0.000058% chance that any one person will be afflicted. Also, if Dr. Burden assumed impact in a highly populated location (population > 5,000,000) then one needs to determine the odds of such an impact and adjust the end result as well. And there are other consideration.

    I could go on, but I will begin to ramble. Dave

  • It's taking momentum from Jupiter, not mass, not gravity. Gravity is the force that mediates the interaction, but in the end, it is only the momenta of the two bodies that is different.

    Bingo Foo

    ---

  • Actually, I almost read it that way. I laughed when I saw 'wend' on slashdot. Being its not something everyone would know, I posted it as "no score +1 bonus". Hmm, poll topic: While, Until, Loop, Wend, Goto .

  • Sorry, the CCD is 1024x1024. Gotta wait for the mosaics.
  • worries about those parking building where you drive in circles the same way going in as you do coming out ... and that that will cause the earth to spin down ..... we have a special place in hell for you ..... running in circles making up for all the people driving in parking buildings ....
  • This site is pretty much slashdotted. I'm setting up a mirror at http://dotslash.dynodns.net/00/12/04/1946254/ [dynodns.net].

    I've got all the jpg's and the .html page so far. The gifs are hard to get for some reason. I've edited a copy of the html page [dynodns.net] so that the img references point to my own mirror, but since all the inline images are the gifs, it doesn't look that good yet. If you click on the jpg links below the images, they are there. I'm not even gonna worry about the tiffs.

    As always with my mirrors: This ain't my work. don't blame me for the problems with the content. I may have made slight changes to the html to make the images work on my machine. If you own or created this work, I'm just trying to do you a favor; if you don't want me to, just mail me. I usually pull these down within a while anyway.

  • Keep in mind that a black hole, as far as orbital mechanics is concerned, is no different than any other object of the same mass in the same orbit. If you replaced the moon with a black hole of the same mass, it would produce pretty much identical gravitational effects as the current moon does. The biggest difference would be the extremely high energy radiation emission that would occur when something falls in. That would be the sort of thing that might ruin your day.

    As far as this Space Debris Protest page, the author seems to underestimate the vastness of space. The situation is similar to you being the only person in the world and throwing the only bottle into the ocean. Realistically, without some way of tracking it, you have no chance of finding that bottle again. The difference in space is that the bottle is too large an example and the ocean is too small by something like 10 orders of magnitude. Eventually, someday, mankind will forget that the Pioneer and Voyager probes are there. And, realistically, no one will ever find them.
  • as a non-republican conservative (i'm independent but voted bush, but that's another story) i listen to rush a bit. he is so full of himself it's not funny. half the quotes he cites these days are quotes of HIMSELF! now before anybody says 'hey, you're just one of those liberal whiners trying to discredit rush' (alright, probably nobody will say that because it would be retarded) i must repeat... I VOTED FOR BUSH AND I STILL HATE RUSH LIMBAUGH! okay. rant off.

  • Ok, it seems like everybody got this wrong. They're not comparing Cassini to Hubble, they're comparing the resolution of the pictures from Cassini to the resolution of pictures from Hubble.
  • In order to take time exposures CCD's must be chilled to cryogenic temperatures. Very sensitive CCD's are also sensitized in other exotic ways, such as by "drifting" atoms of dopants into the substrate so as to carefully control their distribution.

    Detector design is an art, and these imagers are not the ones you buy in cameras at Wal-Mart or even in the back of amateur astronomy magazines. They are hand made one at a time and only the best of the best individual samples go into space.

    These detectors are easily ruined. Long before the CCD melts its high sensitivity can be ruined as excessive temperature and radiation scramble these carefully arranged structures. They will still function as CCD's, but the characteristics which were achieved at such great cost will be ruined. This happened to a relative of mine back in the 70's when he was on vacation, and a coworker let the liquid nitrogen run out on one of his gamma ray detectors. It still detected gamma rays after its day at room temperature, but the energy peaks were broad and flat instead of nice and sharp as their research required.

    The Hubble could focus on the Earth and Moon if the controllers wanted to risk trying, say, aiming at the night side. But they do not want to risk the usefulness of their detectors for faint deep-space objects on trying to resolve Neil's footprints.

    Hubble did photog a near-earth asteroid awhile back that was passing at Moon-like distance, but I believe the problem with the Earth and Moon is the sheer size of highly illuminated area. And imaging a near-new Moon wouldn't help because, of course, then the Moon is mostly dark because the Sun is behind it.

  • That voice, btw, is David Thewlis from the Mike Leigh movie Naked. check - imdb [imdb.com]
  • That damn storm is bigger than our entire planet. You probably wouldn't even notice it if you were in it -- you'd just be floating around in a mass of, well, call it air, with no idea that the "local" mass the size of North America you're floating in is travelling at thousands of km/h with respect to the rest of Jupiter.
  • I'd forgotten the correct term for this particular device, but it is technically a thermonuclear battery, as the breakdown of the plutonium results in thermic energy, which is converted to electricity by a very advanced thermopile.
    This plutonium is glassified. Entrance into the atmosphere would likely create either single-molecular concentrations locally (remember, long way from space down to earth) or giant chunks. These giant chunks pose next to no hazard for three reasons: the radiation they generate can be stopped by a piece of paper, so if a kid doesn't eat them, you're fine. The US and other governments would be *very* interested to recover the core, as it is quite expensive and easily reusable (two known failures involving RTGs(correct term), and in one case, whole core reused, other case it broke into small pieces, but did not become dust). Three, the plutonium, after being glassified, is devilishly hard to turn into bomb-grade plutonium, as someone else has pointed out, that is a *higher* number isotope, so it can't be reduced, it must be augmented, and that is just as easy to do with Uranium-235, which is far more common. However, if one were to reduce part of this isotope to create an augmented amount, the augmented amount, assuming perfect efficiency, would still be no where near enough to create critical mass. If one were to attempt to reduce the plutonium to U-235 (I don't know if this can be done, just hypothetical), there still wouldn't be enough, because in nuclear bombs, there's no such thing as a small bomb. Even an extremely efficient multi-stage bomb uses considerably more uranium than that, not to mention the plutonium in the trigger and the deuterium and tritium needed.
    The fact is that there isn't a single major risk factor associated with the use of this thing. These things have been investigated by every reputable environmental group and have been given a clean slate by all. However, future use is in doubt simply due to lobbying efforts by people who see nuke and go nuts. That's what's sad, because these things are incredibly cost-effective. The same amount of energy from a chemical source would be huge. One of these batteries can produce 500 watts for thirty years.
  • Back before nuclear paranoia, there was a plutonium-powered consumer product - the nuclear-powered pacemaker. About 70 are still in use [uiuc.edu], implanted in people. Those people don't have to undergo pacemaker battery replacement surgery, unlike most pacemaker users.

    Those pacemakers use plutonium encased in tungsten inside stainless steel. Testing on those things was extensive. They will survive bullets at point-blank range and cremation.

    Today, people are horrified by the concept of an implanted nuclear device, but the track record of these holdovers from the 1950s is pretty good.

  • "As far as the other comment, that the Pu238 "can't" oxidize, well, I suppose that depends on a lot of factors. It isn't supposed to oxidize, just like launch vehicles aren't supposed to explode. Personally I think if they screwed up badly enough to hit the earth dead-on at 30K+km/h that it would be hard to imagine all the Pu remaining in solid form regardless of any attempts to protect it."

    But you're utterly missing the point here. They're using plutonium dioxide. It's already oxidised, and it's not going to oxidise anymore. Period!

  • Is it just me or would anyone else not want to be caught up in that swirling mass on the surface there. :)

    .ph0x
  • Cool, thanks! I've always wondered where that come from.
  • Love the shot of Jupiter with Ganymede off to the side.

    Meanwhile, my own efforts to launch a space probe meet with minor setbacks... [dragonswest.com]

    --

  • "Going for -100 Karma"?

    Mod this guy up!


    .-. .- -.. .. --- -....- .- -.- - .. ...- .. - .-.- - ...-.-
  • Probably a stupid and half-informed question, but here goes. Isn't hubble meant for taking pictures outside our solar system. A friend of mine, here's the half-informed bit, told me anything in our solar system would ruin hubble being "too bright", the idea being hubble is meant to view stellar bodies much further away... Sorry if it's a dumb comment but comparing this to hubble seems odd.

  • Now let's worry about gravity conservation (Score:3)

    by Hairy_Potter ( 219096 ) on Monday December 04, 2000 @11:47AM (#582621) Homepage
    Ok, the plutonium is gone.

    Now let's tell those green folks about how gravity assist steals energy from Jupiter, and may cause Jupiter to fall into Earth's orbit!

    I'm sure we can prove it with a few strategic Newtonian equations.
  • Mirror it fast! It's gonna go down hard when /. effect kicks in.

  • Cassini is the sweetest probe ever (Score:5)

    by XneznJuber ( 204781 ) on Monday December 04, 2000 @11:46AM (#582623)
    The Cassini Orbiter's mission consists of delivering a probe (called Huygens, provided by ESA) to Titan, and then remaining in orbit around Saturn for detailed studies of the planet and its rings and satellites. The principal objectives are to: (1) determine the three-dimensional structure and dynamical behavior of the rings; (2) determine the composition of the satellite surfaces and the geological history of each object; (3) determine the nature and origin of the dark material on Iapetus' leading hemisphere; (4) measure the three-dimensional structure and dynamical behavior of the magnetosphere; (5) study the dynamical behavior of Saturn's atmosphere at cloud level; (6) study the time variability of Titan's clouds and hazes; and, (7) characterize Titan's surface on a regional scale. The spacecraft was originally planned to be the second three-axis stabilized, RTG-powered Mariner Mark II, a class of spacecraft developed for missions beyond the orbit of Mars. However, various budget cuts and rescopings of the project have forced a more special design, postponing indefinitely any implementation of the Mariner Mark II series. Cassini is currently planned to take a similar tour of the solar system as did Galileo, referred to as a VVEJGA (Venus-Venus-Earth-Jupiter Gravity Assist) trajectory. Several opportunities exist for Cassini to make observations of asteroids, although exact encounters remain to be determined after the spacecraft has been launched as it depends on the launch date. Current plans call for an arrival in June 2004. Shortly after entering orbit around Saturn, Huygens will separate from the Cassini orbiter and begin its entry into the atmosphere of Titan. Cassini is then expected to make at least 30 loose elliptical orbits of the planet, each optimized for a different set of observations. Cassini's instrumentation consists of: a radar mapper, a CCD imaging system, a visible/infrared mapping spectrometer, a composite infrared spectrometer, a cosmic dust analyzer, a radio and plasma wave experiment, a plasma spectrometer, an ultraviolet imaging spectrograph, a magnetospheric imaging instrument, a magnetometer, an ion/neutral mass spectrometer. Telemetry from the communications antenna as well as other special transmitters (an S-band transmitter and a dual frequency Ka-band system) will also be used to make observations of the atmospheres of Titan and Saturn and to measure the gravity fields of the planet and its satellites
  • There's something called brightness and contrast control... oh wait... that's on a monitor.

    But your statement could be true. It's too bright, so the quality is really bad (seeing white?). Anything flying close by Jupiter should have better quality than from Earth. And how old is Hubble (last imaging upgrade)? Cassini? Are there any great enhancement between the two times?
    ---

  • Should have said... (Score:4)

    by Chacham ( 981 ) on Monday December 04, 2000 @12:12PM (#582625) Homepage Journal

    appears to be working just fine as it wends its way outward toward Saturn

    Should have said: appears to be working just fine while it basically wends its way outward toward Saturn" Otherwise, you'd get a Wend without While error.

  • but i just can't resist:P. Cassini goes to Jupiter to get more stupider....
  • Oh my, it's not like you see one of those every day. And god forbid we see any moving, talking pictures either.
  • (grin)

    But in this guy's mind, that telescope is probably made by NASA and is rigged to show a false image.

    Clever people, those NASA spooks!

  • The actual danger of a Cassini probe accident to a given person in the probe's disaster area is similar to moving to Denver for a year.

    What's the danger of living in Denver compared to living anywhere else? Or is that just an arbitrary place you picked?

  • I like to spice up my RTG's with a little kayan pepper, if you dice up some Photopolarimeter with carrots and some boiled Plasma Wave Antenna's and stir fry them all in the 3.7 meter High Gain Antenna dish you will have a meal fit for a JPL Engineer!

    Don't forget the chilled Narrow Angle, Wide Angle and Plasma sensors for dessert! Mmmm now thats good eatin'

    Capt. Ron

  • Higher altitude means slightly more exposure to radiation from space.


    ...phil
  • very true amongst the laity - they see such issues as black/white "plutonium"/"no plutonium" instead of a range of concentrations from "naturally occuring background radiation" to "reactor core", reasonably acceptable risks and potential benefits, etc. I went back home once to find the local yocals were all up in arms about a new school w/ a furnace emitting "carbon monoxide". When I asked about "how much CO, what concentrations were measured" it was met with incomprehension and restating that "they found CO in that new school" - pointing out that there is CO in the air we're breathing now, just a very small amount, does no good either. The herd got spooked and were stampeding and the politicos had to man the media machines to restore calm and reason. Gawd, I'm glad I'm not the plumber in that hickville.
  • Please liberals (idiots) stop acting like stupid animals ..

    This is the biggest problem with Rush .. namely, that he exists for little other reason than to fan the flames of hatred and turn people against each other. Case in point: you take a large segment of the population (progressives), nearly all of whom you have never met before (and never will meet) and call them "idiots", in what is perhaps the most blatant ad hominem blanket statement I've heard all day. You then accuse them of acting like animals and not thinking!

    Hint: Calling up some blowhard extremist whose outlandish views have relegated him to the obscurity of AM radio and shrieking "MEGADITTOS!" into the phone does not constitute thinking. It is lemming behavior, pure and simple. The vast majority of people have better things to do than listen to a hysterical, truculent, right-wing nut spew vitriol all afternoon.

  • Re:No one was hurt? still != it's all good (Score:3)

    by phil reed ( 626 ) on Monday December 04, 2000 @12:23PM (#582634) Homepage
    Even if we assume that none of the cancers forecasted has arisen (and that's an absurd assumption to make, since cancers take decades to appear in exposed populations)...

    Um. None of the forcasted cancers are ever going to show up, since the uncontrolled reentry of Cassini into the earth's atmosphere was a prerequsite for the cancers to happen, and Cassini didn't reenter the atmosphere. Or weren't you paying attention?


    ...phil

  • Well, to act as devil's advocate, it's possible this guy was just joking. *shrug* :) I'd like to think that rather than call it a troll, because as a troll, it's really not very good...
  • But If Cassini Hits Jupiter It May Affect The Interplanetary Balance And Cause Earthquakes And California May Fall Into The Ocean!!!!

    Oh, yeah.. :-)

    Actually, I know Jupiter has little to do with Earth's tectonic plates. And the danger from plutonium batteries is less than that of your favorite room being in the basement.

  • how can excess photons damage anything nonorganic?

    What has being organic got to do with anything? If you point the HST at the Sun (or any telescope w/o a proper filter for that matter) you will literally melt the CCD. (Think ants under a magnifying glass here). The HST contains a fail-safe program that automatically shuts the door if the telescope is pointing to within 20 degrees of the Sun to prevent damage to the cameras. Someone else mentioned that it is unable to image the Earth or Moon as well. This is true, I think, because they are too close - it can't focus on something that near.

  • In 2001 the book the monolith was on Iapetus, in the center of the bright side -- reminding David Bowman of an eyeball with the monolith as its pupil. Of course, the movie moved the monolith to Io's Lagrange point, and Clarke decided to follow the movie rather than the original book when writing the sequel 2010 because more people were familiar with it.

    But originally, Discovery had been planned as a two-way Jupiter probe which was rerouted to become a one-way Saturn probe whose crew would go into hibernation after doing their duties and await rescue by the as-yet-unbuilt Discovery II. In this scenario it made more sense for HAL the computer to go crazy because it had to keep the secret from Bowman and Poole on the outgoing journey (though you'd have to think they might suspect something big was up with such a large change in mission plan).

    So I'm still waiting to see the pix of Iapetus. You will notice that Iapetus is one of Cassini's particular targets...

  • heh. at least i didn't tell you about my shuttle cock
  • i suspect, contain an unlikely assumption that the Po battery on a spacecraft, would be fully 'atomized' or powderized on reentry to the atmosphere. however i would think that chunks and bits might survive intact(assuming that in the unlikely event the Ir capsule and ablative shield even broke open at all in the first place) and these would obviously pose considerable hazard.

    "....from a meteor strike than from a failed mission with a thermo-nuclear battery."

    Whoa! thermonuclear battery! i didnt even know they were invented yet! did you mean nuclear thermoelectric battery?....maybe?



  • But If Cassini Hits Jupiter It May Affect The Interplanetary Balance And Cause Earthquakes And California May Fall Into The Ocean!!!!

    That's all? I heard that it would effect the Space-Time continuum and Biff would take over the world :)

  • The reason people were upset with Cassini was that it was different from preceeding probes in three ways:

    1. It used the Plutonium isotope 239, rather than the more common 235. Pu239 is more reactive (has a much shorter half-life) than 235; this makes it better fuel for an RTG but makes it much more dangerous if you inhale a particle.

    2. It used an especially large amount of this especially dangerous isotope of Plutonium.

    3. In addition to the at launch risks (of course launch vehicles never blow up, right? The Challenger crew will back you up on that one) Cassini had to make not one but two near passes by Earth, using it as a gravity handle in order to get out to the outer Solar System. Of course NASA would never drive a spacecraft into a planet, just look at the job they did of inserting Mars Climate Orbiter into its current, um, location.

    In any case like all risk calculations in matters nuclear the thing comes down to a multiplication of very large risks by very small probabilities, and in this case NASA didn't blow up the launch vehicle or drive the spacecraft into the planet. Had they done either there is a good chance the RTG would have survived re-entry intact; it is designed to do that, just as the spacecraft is designed not to blow up or drive into the planet, and usually those designs work.

    However, there is a possibility that, in the unlikely event of a re-entry (particularly being driven into the planet during a gravity-handle exercise) the RTG would have breached. This would have been a very bad thing. Plutonium oxidizes readily into a very fine powder which can remain suspended in the air for amazing periods of time. Inhaling even one microscopic particle of this stuff (much worse than Pu235, which is bad enough) pretty much dooms you to lung cancer, at a minimum. You can argue with this if you feel like looking foolish but it's well known what happens when a particle of Pu gets embedded in lung tissue; every alpha particle passes through several hundred cells before it stops, and eventually one of them is going to do major mischief.

    Now, if this happened it's likely that life would have gone on for most of us just as it has gone on after Chernobyl and Three Mile Island -- both accidents which have a long anecdotal and statistical history of ensuing mortality, which has been whitewashed, swept under the rug, or very occasionally outright covered up (ever try to get by-county infant mortality stats for Pennsylvania the year after TMI?). But it would indeed not be the End of the World (tm).

    Is the smallish risk of that worth the pictures we're getting now? I am personally inclined to say yes. But then, it would probably be someone else who got lung cancer if the worst-case accident happened. The people who protested the mission have their point, which is that it's not my right to make that decision for them. I may not agree with them but that does not make them stupid or venal, and it's tiring to see the people I supposedly agree with taking the moral low road by making fun of them and refusing to get their point.

  • Ah, but how do you KNOW it will be there if you go out and look for it tomorrow? How do you KNOW it is there when there are clouds or it is daytime?

    This is why we have to send spacecraft to all these planets, to spray them with UBIK. Otherwise we could wake up one day and find out they've turned into hair dryers or washed-up Presidential candidates floating in the sky.

    (Phil Dick, who wrote UBIK (first), had some kind of epiphany in 1974 after which he came to believe that the entire world was an illusion and that we are really still reliving the years after Christ's death over and over, presumably until we get things right or see past the illusion. And the guy continued to write really good SF.)

  • "This would have been a very bad thing. Plutonium oxidizes readily into a very fine powder which can remain suspended in the air for amazing periods of time. Inhaling even one microscopic particle of...."

    uhm, right, which is why they already oxidized it and melted the oxide into solid glassy chunks. it's not going to powderize any more easily than a coffee cup.

  • 1. It used the Plutonium isotope 239, rather than the more common 235. Pu239 is more reactive (has a much shorter half-life) than 235; this makes it better fuel for an RTG but makes it much more dangerous if you inhale a particle. 2. It used an especially large amount of this especially dangerous isotope of Plutonium.


    Pu-235 has a 25.3 minute half-life. The one they use is Pu-238 with a half life of 87.7 years, so that the power provided during the first 10 years of the mission is more or less constant. Pu-239 has a half life of 24100 years. My data comes from 1996 edition of the Chart of the Nuclides (by Lockehhed Martin & GE Nuclear). I tend to trust it, which means that you are wrong. Also, Pu-235 is not common at all. As with any other isotope of Plutonium, it does not exist in nature. The most "common" in the sense of quantity available is Pu-239, which is used for weapons.
  • "The third panel shows near-infrared reflected sunlight at a wavelength where the gas methane,an important constituent of Jupiter's atmosphere, absorbs strongly."

    I remember an article that talked of the US wanting to blow up the moon... imagine igniting all that methane! How long would it burn for?
    heh
  • Well, it isn't a stupid question, but your friend is wrong. Hubble has imaged various planets in our solar system repeatedly, but it can't point at objects too close to the sun for the reasons you cite.

    In fact, Hubble recorded some great pictures of Shoemaker-Levy's plunge into Jupiter several years ago. Here: Hubble Images of Jupiter and a Comet [stsci.edu]

  • I guess Kubrick was wrong: there's no sign of the black monoliths.
  • Hmmm.. you seem to have a few facts confused. The cancer risk posited was if the craft reentered the atmosphere on it's flyby. Chances of which were extremely low. Those cancers will never appear because the circumstance under which they could have never materialized. Additionally, an increase of 3500 some odd cancers spread over the entire population of earth would be statistically insignificant (unless of course you were one of the 3500), there would be no real way to measure it, it would be lost in the noise..

    And as for the "Mercury capsule conflagration", that was Apollo 1, the astronauts were running a routine practice session. There were a number of mistakes that contributed to their deaths, not least of which was an inward opening hatch and a pure oxygen environment at 1 atmosphere.

    jim

  • Did anyone else see something strange in the Jupiter photos? A black object floating near Jupiter? Kinda like a long rectangle, black, no visible surface features. Looks like a large Hershey bar...

    www.matthewmiller.net [matthewmiller.net]

  • Re:No one was hurt? still != it's all good (Score:3)

    by Psion ( 2244 ) on Monday December 04, 2000 @12:26PM (#582651)
    Anne Marie,

    With all due respect, I wonder how even 120 people could contract fatal cancers. I guess, if someone used a linear, no-threshold model of radioactivity's effects and applied it to the entire population of the world. But realistically, the biggest danger from those RTGs was if one re-entered and hit you on the head. It wouldn't be pretty, but it wouldn't be cancer, either.

    I remember how the media really pushed the controversy in the days leading up to Cassini's launch. CBS had footage of this one poor girl (she may have been around 14), crying in absolute terror as Cassini launched because she honestly believed all life on the planet was about to end. That was the product of the scare-mongering that people pushed. I wonder how many people worked themselves into genuine stress-induced problems because of the alarmist hand-wringing by the anti-nuke crowd.

  • Don't we have to unearth TMA first? Is there a magnetic anomaly in the Tycho crater on the moon? Maybe he was just off by a couple of years. I mean, we've only just started on the ISS, and don't even have a moon base yet. Clarke simply got his dates mixed up.
  • "wake up people, cassini does not exist and for that matter NEITHER DOES JUPITER"

    So when I take my telescope into my backyard and see that big non-twinkling globe with the four dots that seem to go around it when I look every night, or to a larger telescope at a local planetarium and actually see the cloud bands and the great red spot for myself, I'm looking at a governemtn conspiracy?

    Oh right, it's the government chip implaneted in my brain to transmit govt approved images into my eye. :)

    (why can't I just obey the sign "do not feed the trolls"...)
  • The GIAJ (Gravitional Industry Association of Jupiter) has sued Earth for illegally stealing Jupiters gravity, claiming that it "hurts the mass that generates the gravity as less and less comsumers would be interested in paying for a service it can aquire for free".

    NASA commented on it's use of "free" Jovian gravity claiming that "By allowing space probes to use gravity, more consumers would be exposed to it and therefore more interested in its use / application. We also give a venue for the discovery of new massive objects and help them advertise the fact that they too produce gravity...", NASA made no furthur comments...

    Capt. Ron

  • LOL!

    Too bad I posted earlier, or I'd mod you up +1 for funny.

    Ahh, the memories of the good old days of GWBASIC and PCDOS
  • Pu-235 has a 25.3 minute half-life. The one they use is Pu-238 with a half life of 87.7 years, so that the power provided during the first 10 years of the mission is more or less constant. Pu-239 has a half life of 24100 years.

    My bad, what comes from posting after working all weekend instead of doing weekend stuff. I have been writing a story that involved the conversion of Pu239 to U235 for longer-term (100's of millions of years) use, and the number stuck in my head.

    As far as the other comment, that the Pu238 "can't" oxidize, well, I suppose that depends on a lot of factors. It isn't supposed to oxidize, just like launch vehicles aren't supposed to explode. Personally I think if they screwed up badly enough to hit the earth dead-on at 30K+km/h that it would be hard to imagine all the Pu remaining in solid form regardless of any attempts to protect it. Other than the isotope goof I stand by the sentiment of my original post.

  • hey im sure there are a few rocks whirring about in that storm there, that would hurt. Christ im glad i live on a stable planet.

    Well I wasn't referring to the people mind you. :)
  • Hmmm, don't you mean converting U-238 to Pu-239 using U-235 burning breeder reactors? Anyway, RTG's use either Plutonium carbide or dioxide, which are more or less ceramic compounds, and are made into large pellets when used as RTGs. These pellets will not break into dust on reentry. There have been cases of satellites using these crashing down with the RTG box recovered almost intact. Of course there are cases of satellites using older type RTGs (like SNAP-9) that have broken up and contaminated some area, but the level of radiation was not much above the average, i.e. going on a long plane flight would result in more exposure.
  • It wouldn't burn at all. Methane burns on Earth because there is oxygen in the atmosphere to combine with (this is itself a very "unnatural" condition created by living things). The atmosphere of Jupiter is chemically stable as far as we can tell; if you wanted to burn something, you'd have to haul an oxidizer there to combine with all that free methane.
  • Re: the conversion, this involves some folks with very long-term goals and it was worth their while to burn Pu242 (a dwindling supply) to power cyclotrons to irradiate U238 (unused and decayed fuel) with 25eV neutrons to make Pu239. When the Pu239 decays it becomes U235, which has a half-life of 7 ex 8 years (which is why there is still a little of it around).

    The "standard" Pu isotope used in bombs and reactors is Pu242, half life 50,000 years. Pu239 does have a half-life of 24,100 years, and Pu238 92 years. I'm sure it is Pu238 on Cassini. Of course all these isotopes are "rare" (=nonexistent) having gone to U238 in the aeons since the original supernova formed the cloud that birthed Sol. But in the cores of breeder reactors it's Pu242 that's common, and Pu238 the more energetic, unusual, and dangerous isotope that was isolated (no doubt at great expense) for use on Cassini.

    And again, I would expect the RTG to retain its integrity if it re-entered from LEO; that's what it's designed to do. Surviving a head-on collision with the ground at escape velocity is an entirely different thing, which has never been tested.

  • Pu-242 is not fissile because it has an even number of nucleons. Therefore it cannot be used for a bomb. Bombs use Pu-239 as I said already, or Pu-241 (but I'm not sure about that one).
    FYI, here is a list of the common fissile niclei:
    U-233, U-235, Pu-239, Pu-241
  • Two totally different animals with two totally different purposes. One is for deep visual space exploration from a close proximity and maintainable source. Think of the other as a throw away camera. The throw away camera just happened to come with lense that was built for raw imaging and not xray scans like the Hubble.

  • I can see it now. (Score:4)

    by Raymond Luxury Yacht ( 112037 ) on Monday December 04, 2000 @11:58AM (#582663) Homepage
    Cassini: I beg your pardon, but you wouldn't happen to be Jupiter, would you?

    Jupiter: Why, yes.

    Cassini: Nice to meet you! I'm Cassini.

    *sniff* You know, these probes make the solar system a kinder, gentler place to live... chokes ya up, don't it?

  • Re:Better than Hubble (Score:4)

    by NOC_Monkey ( 73018 ) on Monday December 04, 2000 @12:00PM (#582664)
    Hubble actually does have the capability of imaging planets in the solar system. In fact, that's exactly what the WF/PC2 [stsci.edu] (Wide Field/Planetary Camera gen. 2) is for. There are some stunning images that Hubble has taken of several solar system bodies [stsci.edu], including the Shoemaker-Levy 9 encounter [stsci.edu] with Jupiter [stsci.edu].

  • Probably already well known (Score:5)

    by Weirdling ( 147741 ) on Monday December 04, 2000 @12:02PM (#582665)
    The actual danger of a Cassini probe accident to a given person in the probe's disaster area is similar to moving to Denver for a year. These anti-nuke guys simply hype up the fact that plutonium is toxic without taking into account the fact that the toxicology of a single particle is minute and one has to have a significant amount inhaled in order to suffer any significant result. I did a report in college on this particular matter (Cassini had not yet been launched), and my report, which I no longer have, concluded that Cassini posed no significant threat whatsoever and demonstrated that my findings were backed up by the findings of several of the less-rabid environmental protection groups.
    As a matter of fact, one is far more likely to die from a meteor strike than from a failed mission with a thermo-nuclear battery.

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