Slashdot Mirror

← Back to Stories (view on slashdot.org)

Huygens Probe Prepares for Saturn Moon Landing

Posted by CowboyNeal on from the setting-down dept.

Nathan writes "A probe is about to land on one of Saturn's 35 moons, Titan. The probe is a collaboration with NASA, the European Space Agency and Italy's space program. The probe is apparently about the size of a Volkswagen Beetle. This landing should lead scientists toward new information about the atmosphere and the magnetosphere."

16 of 273 comments (clear)

  1. Timeline and (better) coverage... by John+Miles · · Score: 5, Informative

    ... at SpaceFlight Now

    It'd be worth staying up for, but the last time I did that, I jinxed the Mars Polar Lander. :(

    If the Huygens timeline executes as planned, it will rank among the coolest engineering achievements in history. It will also have happened thanks to one guy who kept his eye on the ball when nobody else was paying attention.

    --
    Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.
    1. Re:Timeline and (better) coverage... by wallitron · · Score: 4, Informative

      Nice save.

      "In short: Cassini is at Saturn, and about to launch the Huygens probe into Titan's atmosphere (splashdown 14th January 2005). The communication link between Huygens and Cassini was not thoroughly tested before launch. Some thoughtful engineer realised this might be a problem, and after some pushing against resistance, managed to test Cassini's response to how they expect the signal from Huygens to look. Surprise suprise, Houston we have a problem. Turns out, the original engineers took account of doppler shift in the carrier wave, but not in the encoded data. D'oh! Problem is encoded in firmware, can't be fixed after launch. Double d'oh! So instead, they've altered Cassini's trajectory to eliminate the doppler shift. Hurrah for Boris Smeds!"

      http://gimbo.org.uk/archives/2005/01/boris_smeds_v s.html

    2. Re:Timeline and (better) coverage... by wass · · Score: 3, Informative
      Wow, that IEEE link one was one of the most informative links I've come across on slashdot, pretty illuminating. It's amazing that the communication system wasn't fully tested. Here's a few quotes for those too lazy to read the article (a bit long) about the problem that a Swedish ESA engineer caught, while everybody else (NASA + ESA) didn't want to consider it.

      It's a real shame that the private Italian subcontractor didn't allow transparency in the plans for the transmitter. I mean, this is a SCIENCE mission, not a competition for profits. (The company viewed NASA as their competitor, and the transmitter as proprietary).

      The board discovered that Alenia Spazio SpA, the Rome-based company that built the radio link, had properly anticipated the need to make the receiver sensitive over a wide enough range of frequencies to detect Huygens's carrier signal even when Doppler shifted. But it had overlooked another subtle consequence: Doppler shift would affect not just the frequency of the carrier wave that the probe's vital observations would be transmitted on but also the digitally encoded signal itself. In effect, the shift would push the signal out of synch with the timing scheme used to recover data from the phase-modulated carrier.

      Because of Doppler shift, the frequency at which bits would be arriving from Huygens would be significantly different from the nominal data rate of 8192 bits per second. As the radio wave from the lander was compressed by Doppler shift, the data rate would increase as the length of each bit was reduced.

      Although the receiver's decoder could accommodate small shifts in the received data rate, it was completely out of its league here. The incoming signal was doomed to be chopped up into chunks that didn't correspond to the actual data being sent, and as a result the signal decoder would produce a stream of binary junk. The situation would be like trying to watch a scrambled TV channel--the TV's tuned in fine, but you still can't make out the picture.

      Alenia Spazio wasn't alone in missing the impact Doppler shift would have on the decoder. All the design reviews of the communications link, including those conducted with NASA participation, also failed to notice the error that would threaten to turn Huygens's moment of glory into an embarrassing failure.

      Alenia Spazio's insistence on confidentiality may have played a role in this oversight. NASA reviewers were never given the specs of the receiver. As JPL's Mitchell explained to Spectrum, "Alenia Spazio considered JPL to be a competitor and treated the radio design as proprietary data."

      JPL's Horttor admitted that NASA probably could have insisted on seeing the design if it had agreed to sign standard nondisclosure agreements, but NASA didn't consider the effort worthwhile, automatically assuming Alenia Spazio would compensate for the changing data rate.

      --

      make world, not war

    3. Re:Timeline and (better) coverage... by Ford+Prefect · · Score: 2, Informative

      Something about that makes the hairs on the back of my neck stand on end. Goodness knows how he feels today!

      I've got a copy of the ESA Bulletin journal from either January or February 1985 which was given to me years ago by a friend of the family - and one of the main articles is about the Huygens probe, in a form very similar to the final version launched in 1997. I think I ought to scan the article and post it online, just to give people an indication of how thoroughly planned these projects are. Unfortunately it's at home, and I'm in Brussels.

      I was five years old when they had a detailed design for this probe. Now that's scary. :-)

      (Oh, and captain, we get signal! Now just waiting for main screen turn on... ;-) )

      --
      Tedious Bloggy Stuff - hooray?
  2. Here is a Countdown by mowler2 · · Score: 4, Informative

    Here is the official ESA countdown! At the moment, it's only 4 hours left! :) However, after landing, it will take another 5 hours before the data starts coming in, and we know wether it was a success or a failure.

    In the application, you can also fastforward and see what Cassini does in the coming years.

  3. For those interested in discussing this on irc by yuriwho · · Score: 4, Informative

    please join our irc channel #space on irc.freenode.net

    This channel is devoted to discussion of space science, current, past and future space missions.

    This channel is frequented by a lot of knowledgeable folk. And please keep the discussion on topic ;-)

    Y

    --
    no sig.
  4. Not NASA. by i41Overlord · · Score: 4, Informative

    The probe was built by the ESA, not NASA. Cassini is NASA, Huygens probe is ESA.

    And NASA's Mars rovers are still going strong, whereas the ESA's Beagle is just a crater.

  5. Re:35 moons! by gnuman99 · · Score: 3, Informative
    While none of us have experience in checking out other solar systems, I'll be willing to hypothesize that, in this galaxy, there are very few planet/satellite combinations that are very comparable in mass/size (as the Earth/Moon combo is).

    Like the Pluto/Chiron?. Closer ration than Earth/Moon.. So there is a closer ratio example in *our* system.

    Hypothesis are suppose to educated guesses based on *current* knowledge. Thus, you are not hypothesizing, but just guessing.

  6. But Not ESA Either by Z+Chameleon · · Score: 5, Informative

    Beagle 2 was not an ESA probe but rather a British project which piggybacked on ESA's Mars Express orbiter (which is going strong by the way).

  7. More coverage: NASA TV and Planetary Society blog by FleaPlus · · Score: 2, Informative

    The Planetary Society's Emily Lakdawalla is running a weblog from Huygens mission control in Darmstadt, Germany. This weblog will be updated as events happen, so it should be interesting to watch.

    It also looks like NASA TV will have live coverage for much of Friday. You can access their video and audio streams here.

  8. Re:Not just images... by the+frizz · · Score: 2, Informative

    Live video feed from NASA TV too.

  9. Re:Good luck! by Anonymous Coward · · Score: 2, Informative

    This time the Italian space agency forgot to account for Doppler frequency shift. Luckily they found a workaround, so not all is lost.

  10. www.esa.int by dolmen.fr · · Score: 5, Informative

    I won't blame anyone who hasn't RTFA for this news, because here is the really interesting link: the ESA (European Space Agency) portal.
    A 346 words article from India Daily is not the most relevant for an ESA project.

    I hope /. moderators would care a bit more when posting news. Recently the interesting links were often missing. A link to a press agency article may be interesting to some, but we have other sources for that. I expect a bit more from a /. news: the poster should at list post links to official sites with deeper information.

  11. Re:Only a few hours until it makes a crater on Tit by KontinMonet · · Score: 3, Informative

    The US engineers did not discover the problem. It was a Swedish engineer.

    Furthermore: "Alenia Spazio (the Italian contractor) wasn't alone in missing the impact Doppler shift would have on the decoder. All the design reviews of the communications link, including those conducted with NASA participation, also failed to notice the error that would threaten to turn Huygens's moment of glory into an embarrassing failure."

    Get your facts right (although being AC, no doubt it was just xenophobic bullshit on your part).

    --
    Did he inhale?
  12. Re:Only a few hours until it makes a crater on Tit by Anonymous Coward · · Score: 2, Informative

    If you really want to find out about what happened about the design of the radio link between Huygens and Cassini and who who exactly discovered the problem and was insistent enough to get it fixed, then read this excellent article in IEEE's Spectrum:

    http://www.spectrum.ieee.org/WEBONLY/publicfeatu re /oct04/1004titan.html

    hint: it was a Swede working at ESA in Germany... so much about team play :)

  13. Re:35 moons! by djc6430 · · Score: 2, Informative

    Planet Claire has pink air, and all the trees are red.