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Space Science

Huygens Wind Experiment Salvaged 207

SeaDour writes "Earlier, it was reported that the data from a critical wind speed experiment onboard the Huygens probe to Titan was completely lost due to someone forgetting to turn on one of Cassini's communications channels. However, it now appears that ground-based radio telescopes from the National Radio Astronomy Observatory were able to record the transmission's many subtle doppler shifts and reconstruct that lost wind data. The winds altered the probe's horizontal rate of descent, thereby producing a change in the frequency of the signal received on Earth. Additionally, the resolution of the radio telescopes was good enough to track Huygen's position to within one kilometer, allowing for the creation of a three-dimensional model of Huygen's descent."
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Huygens Wind Experiment Salvaged

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  • backup (Score:3, Insightful)

    by j1bb3rj4bb3r ( 808677 ) on Wednesday February 09, 2005 @02:55PM (#11621571)
    ... nothing like a little backup.
    • One of the backups, in this case, is the Robert C. Byrd Green Bank Telescope [nrao.edu]. I imagine that the telescope is located on Robert C. Byrd Highway, down the road from the Robert C. Byrd FBI Fingerprinting facility and just around the corner from the Robert C. Byrd Memorial High School.

      Man, the Esteemed Senior Senator from West Virginia sure does a fine job of delivering the bacon...

  • by suso ( 153703 ) on Wednesday February 09, 2005 @02:55PM (#11621572) Homepage Journal
    is that if that experiment would have been turned on like it was supposed to, probably nobody here would have ever known that it existed in the first place. ;-)
  • by DemiKnute ( 237008 ) on Wednesday February 09, 2005 @02:55PM (#11621574) Homepage
    How can you have a horizontal rate of descent? Was this thing was falling sideways?

    What a strange and fantastic world this Titan must be.
    • by BradleyUffner ( 103496 ) on Wednesday February 09, 2005 @02:58PM (#11621617) Homepage
      It was descending at an angle due strong winds. It's rate of descent could be something like 2ft of horizontal movement for every foot of vertical movement (numbers made up on the spot). It's sometimes called a Glide Ratio.
    • by Anonymous Coward
      It's called a vector. Vectors are broken into a vertical and a horizontal component. The horizontal component came from the wind. Try it here on Earth sometime and report back.

      Cheers,

      ~g

    • Was this thing was falling sideways?

      Everything that falls from space has a horizontal component to its descent.

    • Three people have responded to the original poster's question so far. The two who had a nickname attempted to answer his question while the anonymous coward was content to just be a smart-a$$.

      Anyway, the article was, of course, referring to the horizontal *component* of the descent.

      Don't take it personally DemiKnute...a couple of days ago I got hammered by a lot of AC's just for asking how you could take a picture of something 20K light-years away.

      This is probably why "The Sims Online" failed as well.
  • No Excuses (Score:2, Insightful)

    by fembots ( 753724 )
    I hope it's not making a habit that people can forget something and fix it later, it doesn't work every time.
  • by Dutchmaan ( 442553 ) on Wednesday February 09, 2005 @02:57PM (#11621603) Homepage
    That we have equipment sensitive enough to track a probe's position to within *1* km all the way out on Titan..

    saying it seems rather bland but when you think of how many millions of miles away it is, I think it's pretty remarkable.
  • by Anonymous Coward on Wednesday February 09, 2005 @02:57PM (#11621608)
    ...the scientist who forgot to switch the experiment on, making "wooshing" sounds into a mike. "We got the data back, nothing to be embarassed about here, no sirree!"
  • R.E.S.P.E.C.T. ! (Score:5, Insightful)

    by selderrr ( 523988 ) on Wednesday February 09, 2005 @02:59PM (#11621627) Journal
    if anyone at nasa is dumb enough to read slashdot : you guys rock !

    Seriously : most people would give up, blaming someone else. It takes a true fighting spirit to try and recover from what someone else has fucked up.
    • Re:R.E.S.P.E.C.T. ! (Score:2, Informative)

      by Docrates ( 148350 )
      NASA? you do realize Huygens was a ESA+NASA effort...and in fact, most of the probe's development was european? NASA's Cassini was the carrier of the probe, but the probe is an European accomplishment first.

      • by selderrr ( 523988 ) on Wednesday February 09, 2005 @03:17PM (#11621836) Journal
        oh puhlease... Must everyone always turn everything into a debate ? Okay, so what. congrats to ESA as well. My post was not about Nasa or esa or Uso or wtf... It's about people being persistent and believing in a solution and an outcome, no matter how big the problem may seem, and no matter how big the fuckup to work around.

        if it eases your xenophobia : I'm european as well.
      • Re:R.E.S.P.E.C.T. ! (Score:5, Informative)

        by jmichaelg ( 148257 ) on Wednesday February 09, 2005 @03:20PM (#11621875) Journal
        Figuring out that the wind data was embedded in the radio signal was an NRAO [nrao.edu] accomplishment.

        It wasn't NASA, it wasn't ESA and it wasn't easy...

      • by i41Overlord ( 829913 ) on Wednesday February 09, 2005 @03:23PM (#11621909)
        How come when Europe does something, people claim that's it's a great European accomplishment and everyone salutes them.

        However when the USA does something and people claim it's a great American accomplishment, people get offended and feel the need to knock NASA?

        It's almost as if the political climate on this forum supports the recognition of someone's feats only if they're considered an underdog?
        • FYI: The slashdot "hive mind" doesn't like having its weaknesses pointed out. Beware the trolls and the mods...

          Excellent point though. I wish I had points to give this post.
        • It's almost as if the political climate on this forum supports the recognition of someone's feats only if they're considered an underdog?

          This is a site of linux zealots afterall....
        • It's almost as if the political climate on this forum supports the recognition of someone's feats only if they're considered an underdog?

          You just have to find the underdog in the story and point them out, and the respect will flow. Humanize it a little.

          It's not the USA that gets props, it's NASA (who's constantly fighting with the Guvm'nt for more funding). Or it's not NASA, it's the overworked and underpaid engineers who found a way to cobble something together out of shoestring and boot leather, push
        • It's almost as if the political climate on this forum supports the recognition of someone's feats only if they're considered an underdog?

          That's not this forum, that's human nature. We naturally resent those in power, those with more money than us, etc. Why are movies always about the underdog winning, never about the current champion kicking ass? It's the same thing. Nietzsche called it the "Will to Power," and he makes an interesting case.
        • "How come when Europe does something, people claim that's it's a great European accomplishment and everyone salutes them."

          Because they are sympathetic and the underdog (not neccesarely in that order).

          "However when the USA does something and people claim it's a great American accomplishment, people get offended and feel the need to knock NASA?"

          That's because, mostly, it's not 'people' in general claiming that, but rather americans claiming it of their own; an opinion not shared by many.

          "It's almost as if
      • Well, smack my head and call me an idiot. I'd been under the impression that the Europeans were wholly responsible for this mission. Thanks to your comment, and a bit of googling, I now have a lot less respect for the European scientific community.

        Sure, they built a dandy little lander, but frankly, how hard is it to design a vehicle that has to detach, decelerate, and deploy a parachute? NASA seems to have literally done the heavy lifting here. The Huygens probe was fairly small, compared to Cassini. NASA
  • by jacksonai ( 604950 ) <taladon@gmail.com> on Wednesday February 09, 2005 @03:02PM (#11621666) Homepage
    that's the first diagnostic question I always ask when fixing something.
  • by nizo ( 81281 ) * on Wednesday February 09, 2005 @03:04PM (#11621681) Homepage Journal
    So basically what they are saying is they should have used the space for some other experiment? The guy spending years setting up an experiment that never got turned on isn't as bad as designing a useless experiment taking up space on the probe. Or was the onboard experiment supposed to be much more accurate?
    • I believe the equipment on-board was necessary to record the wind speeds etc., it was just that the main transmission eq to send the signal back was not turned on.
    • So basically what they are saying is they should have used the space for some other experiment?

      Not really. Cassini would have received a stronger signal, and the changes in relative motion between Huygens and Cassini would have resulted in larger doppler shifts. This would have improved the precision and/or accuracy of the measurements. In addition one of the features of the DWE is the fact that the two oscilators were designed and calibrated to be extremely close to each other in frequency. Without
  • Eh? (Score:2, Interesting)

    The probe was to transmit data on two channels, A and B, Atkinson said. His Doppler wind experiment was to use Channel A, a very stable frequency.

    But the order to activate the receiver, or oscillator, for Channel A was never sent, so the entire mission operated through Channel B, which is less stable, Atkinson said. .....

    Also, he said some of the Channel A signal reached Earth and was picked up by radio telescopes. "We now have some of this data and lots of work to do to try to catch up," he wrote.

    So..

  • by psyklopz ( 412711 ) on Wednesday February 09, 2005 @03:07PM (#11621736)
    So, the experiment itself wasn't saved. They just found another way to get the data (reading the doppler shift in the signal).

    So, here's a good question: why did they need to include the equipment for the experiment in the first place?
    • How about because there's no guarantee that we would have been able to reconstruct the data using land-based radio telescopes? You do recognize that this is an exceptional accomplishment that requires a lot more work (and most importantly, a lot more luck) than having the satellite record this data and send it back to us in digital, error-corrected form, right? Sure, there's no guarantee that we would have gotten the experiment either way, but the odds are a hell of a lot better.

      -chris

    • Actually, it was. Guess which signal they measured the doppler shift of - it was the data signal for this very experiment. The issue was that Cassini forgot to relay it, so they had to rely on the weak signal from Huygens itself.

      Check out some of the other comments to this effect...

      Jw
    • I think it is amusing and sad that in a few weeks the was constructed to replace an instrument that someone spent a couple decades of their lives to make.

      I guess sometimes ingenuity requires a tough problem to solve.

      Maybe when the project started, there wasn't a way to do this with the terrestrial equipment?
    • Well...

      As someone else pointed out. The doppler data we got on Earth depended on the working ultra-stable oscilator [nasa.gov] on Huygens. However, there are some good reasons why it would have been nice for it's twin to be working on Cassini.

      1: The two USOs were designed and calibrated to operate on the same frequency with a high degree of precision. The lack of a similarly calibrated USO on Earth adds a bit of error to the measurements.

      2: Signal strength and doppler shifts measured by Cassini would have been l
  • completely lost? (Score:3, Interesting)

    by i41Overlord ( 829913 ) on Wednesday February 09, 2005 @03:10PM (#11621763)
    From the very beginning it was reported on here that ground based telescopes would be able to record and reconstruct the data.

    This is the first time that I heard them saying that the data was "completely lost".
  • by Jugalator ( 259273 ) on Wednesday February 09, 2005 @03:17PM (#11621839) Journal
    They're quite old anyway, basically from the day after it landed. For example mentioned here [2020hindsight.org].
    Slashdot chose to post about the doomed mission [slashdot.org] instead, which made me believe it was indeed lost... but apparently it was like this all the time.
  • by spanklin ( 710953 ) on Wednesday February 09, 2005 @03:24PM (#11621926)
    A lot of this work was done by the "Green Bank Telescope" aka the Great Big Telescope or GBT. You should check out [nrao.edu] the specs on this telescope. It is the world's largest fully steerable telescope and it is taller than the Statue of Liberty. I was a grad student while this was being built, and was always impressed when I saw presentations about the amount of work that went into creating this instrument. It is not nearly as famous as other telescopes like Hubble or Keck, but is very impressive nevertheless.
  • by Air-conditioned cowh ( 552882 ) on Wednesday February 09, 2005 @03:33PM (#11622016)
    IIRC about half of the picures taken were relayed via the A channel and what we have seen is all B channel stuff only.

    Any chance of reconstructing those images from the ground-based recordings of the A channel, or is the signal so weak that all that can ever be deduced is the carrier frequency, not any data?
    • IIRC about half of the picures taken were relayed via the A channel and what we have seen is all B channel stuff only....Any chance of reconstructing those images from the ground-based recordings of the A channel, or is the signal so weak that all that can ever be deduced is the carrier frequency, not any data?

      There was a long discussion about this on a prior slashdot story. My speculation is that because they appeared to use digital compression algorithms, recovery of the images is probably mostly a lo
  • earning karma in heaven right now....
    • Well then, good ol' Doppler made good for causing problems earlier during this mission problems (The signals from Huygens could not be received by Cassini due to Doppler shift, by getting Cassini into a different orbig (I presume more perpendicular to Huygens, this problem was overcome).

      Bert
  • Inefficiency? (Score:2, Redundant)

    by Telastyn ( 206146 )
    This might seem a little harsh, but why was a wind measuring experiment sent with the probe if we could gather the same data remotely via doppler shift measurements?

    I imagine it's not the same data [or rather the same certainty or resolution], but still, wouldn't the space/weight be better spent on a different experiment if the wind study team could make do with the data gathered from doppler shift analysis?
    • This might seem a little harsh, but why are you posting electronically when you could perform the same communications using mailed letters?

      I imagine it's not the same data [or rather not the same speed and audience], but still, wouldn't the electricty/materials be better spent on something else if you can make do with a pen and paper?

    • This might seem a little harsh, but why was a wind measuring experiment sent with the probe if we could gather the same data remotely via doppler shift measurements?

      They didn't gather all the data solely by measuring the doppler shift on a constant signal, if that's what you're thinking. The bulk of the data was collected wind measuring equipment and transmitted. The doppler shift of this data signal provided additional information. What they're saying is that they not only managed to recover the data sig

    • Re:Inefficiency? (Score:3, Informative)

      Perhaps you should RTFA, or perhaps even this article? [planetary.org].

      1: The DWE consisted of two modules. One on Huygens, and one on Cassini. Without the activation of the Huygens module, we would have had no data for earth-based telescopes to detect.

      2: The DWE carrier signal did double duty as a channel for image transmission. Not only did the receiver screw-up result in loss of DWE data, but it also resulted in the loss of 350 images as well.

      3: Reception by Earth-based radio telescopes was uncertain at the time
  • Yegads (Score:3, Funny)

    by hey! ( 33014 ) on Wednesday February 09, 2005 @03:35PM (#11622051) Homepage Journal
    talk about geek status points. The guy who figured that out must be strutting around like a fricken' god or something, or one of those guys in the movies who does the tap-tap-tap-we're in routine.
  • Fantasic bit of work really, but I bet as just as accurate (or inaccurate, depending if your glass is half full or half empty) as tomorrows weather forecast here on Earth, going by experience...
  • Reminds me... (Score:4, Insightful)

    by biglig2 ( 89374 ) on Wednesday February 09, 2005 @03:44PM (#11622155) Homepage Journal
    ... of a maxim my team has tried to explain to our senior management many times, without sucess:

    "Yes, we will always pull a miracle out of the hat for you when everything goes wrong. But, you should not write your plans with this as an assumption."
  • by behindthewall ( 231520 ) on Wednesday February 09, 2005 @04:14PM (#11622533)
    This hasn't gotten as much coverage, but a design oversight nearly cost all Huygens data. Doppler shift was not accounted for in the signal decode process. The mission plan had to be rewritten to find an alternative flight path that reduced the Doppler shift to within the limited acceptable tolerances. Fortunately, Cassini's approach to Saturn was accurate enough that enough fuel existed to allow this while preserving the latter part of the existing flight plan.

    Of course, in retrospect, maybe earth-based monitoring would have come to the rescue in this event, in an even bigger fashion.

    "Titan Calling: How a Swedish engineer saved a once-in-a-lifetime mission to Saturn's mysterious moon"
    http://www.spectrum.ieee.org/WEBONLY/publicfeature /oct04/1004titan.html [ieee.org]

    Sorry if this is a repeat. Slashdot's search 503-ed on me.
  • ... as Nguyens Wind Experiment.

    The repetition confuzzled me.

  • Makes me wonder why no one is planning orbiting radio satellites to increase this sort of radio reception resolution?

  • Did anyone watch the Daily Show where Jon Stewart was covering the Huygens probe and every time he said Huygens he said it like Professor Frink from the Simpsons? Huuuyyygens!!! Now whenever I see that word I immediately laugh:

    Professor Frink teaching a kindergarten class, pushing one of those popcorn popper thingies with the colored balls inside:

    Frink: "N'hey hey! Ahem, n'hey.... So the compression and expansion of the longitudinal waves cause the erratic oscillation -- you can see it there -- of th
  • So, now they proved that the whole test was redundant and they could have carried a different piece of observation gear, or saved a lot of money or development, or...
  • by qualico ( 731143 ) <worldcouchsurfer AT gmail DOT com> on Thursday February 10, 2005 @12:38AM (#11626976) Journal
    Just to clarify, the "command" to turn "on" the oscillator for Channel A was not sent due to human error.
    So that equates to no data sent to Earth from Cassini for that Channel which contains the wind data and half of the photos.
    Channel B does not have a similar oscillator so it did not suffer from the same problem.

    So my question is, what data did they get, (or could get potentially)?
    Sounds like the photos will be lost because all they seem to have accomplished with the global radar conglomerate was a measurement of Huygens's Doppler shifting carrier wave signal.

    This is probably not as accurate as the direct measurements but will give us a replay of the descent to within 1km thanks to some correlation to VLBI measurements taken on Earth also.

    There is a heated debate between project teams going on in the background as to exactly where the probe landed.
    So this data should do well to help pinpoint the location.

    Because, I made up a collage, Titan's Huygens Collage [spacescience.ca]

    I'm interested in seeing more images. Knowing wind speeds is good data, but personally I'd much rather have more photos for my collage. :) Lager version at spacescience.ca

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