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Space Science

Cassini-Huygens Saturn Orbit Insertion Imminent 205

Posted by simoniker
from the saturnz-return dept.
Anonymous Explorer writes "Fresh off of its fly-by with the Saturnian satellite Phoebe, the Cassini-Huygens craft is set for Saturn Orbit Insertion on June 30, 2004. Cassini-Huygens has a planned four year mission ahead for Saturn and its many moons. With 450 watts of power for the electronics, this mission has plenty enough horses to run the stretch with plenty-o-pep to spare. Thanks to all that power, and the plethora of electronics on Cassini and the Huygens probe, we can now hear sounds from Saturn. Pretty cool stuff! Festivities are scheduled to begin on June 29th with a broadcast of Cassini Saturn Orbit Insertion Press Conference on Nasa TV. SOI [PDF link] will occur after Cassini fires its main engine for 96 minutes, in order to slow down and be grabbed by the pull of Saturn. As always we extend an invitation to everyone to join #cassini on irc.freenode.net and help us celebrate this historic mission."
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Cassini-Huygens Saturn Orbit Insertion Imminent

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  • by Anonymous Coward on Tuesday June 29, 2004 @11:23AM (#9560526)
    ..for transmitting from millions of miles away and some HAMs are using 10 kilowatts upwards just for transmitting earth-to-earth!
  • by vi (editor) (791442) on Tuesday June 29, 2004 @11:29AM (#9560588)
    Remember when Greenpeace and other eco-idiologists wanted to abort the Hygens-Cassini mission due to the Plutonium batteries because they might drop back on earth and contain TEH EVIL RADIOACTIVE PLUTONIUM which would kill seals and cute little children ?
    Lucky the officials at NASA and ESA weren't that stupid and fought off this attack.
    The tremendous success of this mission illustrates how these 21th century idiologists are could stiffle science and cause harm for the whole world.
    It makes me wonder if we could get this done today or in year with the eco rising to power in Europe and perhaps US after the elections, too.
  • by WormholeFiend (674934) on Tuesday June 29, 2004 @11:39AM (#9560692)
    I want to see photos of the rings from inside (the rim? the gap?)...

    BTW, how thick are the rings at the point where the probe is passing through them? How long will it take to clear that space?
  • Sound in space? (Score:2, Interesting)

    by Anonymous Coward on Tuesday June 29, 2004 @11:40AM (#9560700)
    How did they get sound? There is no sound in space (since it requires a medium like the air)... My guess is that the frequency of these "sounds" is close to that of the radiation being measured... Does anyone have the complete information on this?
  • by bcrowell (177657) on Tuesday June 29, 2004 @11:46AM (#9560761) Homepage
    People theorizing about asteroid mining in the past had talked about complicated ways of getting ice out of the rare ice-bearing asteroids. Now that we know Phoebe is icy, I wonder if it ends up being the most practical place in the solar system to get ice. Although it's in the outer solar system, which is inconvenient, that's not necessarily such a big deal with solar-powered ion drive propulsion (as demonstrated by NASA already), which theoretically allows you to send anything into any orbit without paying for energy.
  • Re:450 watts? (Score:5, Interesting)

    by Rei (128717) on Tuesday June 29, 2004 @12:03PM (#9560922) Homepage
    Cassini is powered by the heat of decay of plutonium creating a variation in temperature across a junction of two different metals, which creates electric power (thermoelectrics). It's called an RTG: Radioisotope Thermoelectric Generator. They're not very efficient, but you try carrying a pebble bed reactor into space and operating it by long-distance remote control in zero g..... ;)
  • Only 20 Watts... (Score:4, Interesting)

    by Jott42 (702470) on Tuesday June 29, 2004 @12:31PM (#9561275)
    The travelling-wave amplifier gives only 20 Watts of output power, which feeds into a 4 meter dish antenna. At 8.4 GHz this gives a gain of about 50 dB. EIRP then at 2 MW. (And a free space loss to Saturnus of about 300 dB....)
  • by Idarubicin (579475) <allsquietNO@SPAMhotmail.com> on Tuesday June 29, 2004 @01:17PM (#9561866) Journal
    Oh yeah, and double all those amounts. That is the theoretical maximum that could be derived from the fuel. In practice, the best we can achieve is 40 percent.

    Are you sure? That's pretty close to true on earth, where the cold side of a Carnot cycle is going to be at around 300 K. Space, however, is mostly a nice, big, cold blackbody at around 3 kelvin or so (cosmic microwave background.) That should help quite a bit.

    On the other hand, other posters have noted that the mass calculation neglects the oxidizer that would have to be carried. That works out to being three or so times the mass of the fuel, depending on the specific hydrocarbons chosen.

  • by IronChef (164482) on Tuesday June 29, 2004 @01:50PM (#9562286) Homepage
    Long ago, when I thought I wanted to be an EE, I did a couple of summer internships at JPL. I worked on the Cassini flight computer. My coworkers, especially the lead ASIC designer, were blisteringly smart people. If Cassini fails, it won't be the computer design at least!

    Back then, the project was called "CRAF/Cassini" where CRAF was "Comet Rendezvous/Asteroid Flyby." CRAF was supposed to be the sister ship to Cassini, but it was cut for budgetary reasons. Too bad... with all the design work done how much could it have cost to just build another ship?

    See, we were building this neat computer that would be reused on the next generation of probes, instead of having custom computer hardware for each... but of course it didn't work out that way.

    I was lucky enough to see Cassini (and Galileo) in the Vehicle Assembly Facility. There was an observation deck where you could watch the guys in the clean room building the spacecraft. It was very cool to look down and realize, "that is going to Saturn." Or wherever.

    Cassini is the last of the old school probe designs... a gigantic and expensive. She'll give us a heck of a show.
  • by MooseByte (751829) on Tuesday June 29, 2004 @02:08PM (#9562499)

    "some HAMs are using 10 kilowatts upwards just for transmitting earth-to-earth!"

    Actually, ignoring the 1.5KW max Ham radio ops are legally bound to, most Ham operators operate in the 100 watt range (in the HF freqs == "shortwave"), and there's a dedicated core of low-power enthusiasts who communicate around the world on 5 watts, 1 watt or even a few hundred milliwatts. (The microwatt crew even come out during favorable solar conditions).

    Check out these guys [qrparci.org] for a starting point.

    It varies by spectrum of course (VHF/HF/etc.) but I've personally worked every continent with less than 5 watts using just a homemade wire antenna, no fancy NSA-like array of metal high in the air.

    Antarctica was the most fun - Russian op down there at their research station. Darn neatstuff!

  • by Rhodnius (749829) on Tuesday June 29, 2004 @03:49PM (#9563672)
    In a nutshell, here's how Cassini will interact with the rings during the orbital insertion.

    Saturn right now is tilted, so that the south/"bottom" side of its rings is facing towards the Sun and Earth. Hence, Cassini is approaching Saturn from "underneath" as we see it from Earth. The orbit insertion requires Cassini to pass through the equatorial/ring plane south-to-north as it approaches the planet. It will fire its rocket while on the north side of the rings, and then coast back to the south side on its way back out.

    Now, how is Cassini doing that safely? It's doing so by going through the ring plane where there are no rings. It could be thought of as a "gap", but Cassini really isn't anywhere near the rings when it crosses them. The crossing points are far outside the main mass of the ring system.

    A rough analogy is this. Suppose you lived in Alaska, and had a sailboat named Cassini. Now suppose you had to sail from Alaska to Mexico without bumping into anything. Naturally, you'd pass between Hawaii and the continental US. That's a rough analogue to what's going on at Saturn - the main mass of the rings is like the continental US landmass (and there's a few small intra-ring gaps like the Mississippi River), while there's a few small outside rings sort of like the Hawaiian islands.

    Would it be possible that your sailboat bumped into a rock or debris or something that we didn't know was there? Yes. Is that possibility remote enough that it makes for the safest course to your destination? Also yes.

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