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Space Science

Saving Huygens 267

Posted by michael from the dodged-a-bullet dept.
TazMainiac writes "This months IEEE Spectrum is running an article on how a Swedish scientist discovered that the Titan probe Cassini had a communications flaw that would cause it to lose all data sent back from the Huygens lander as it plunges into Titan's atmosphere. The problem - Doppler effect. The fix: go read the article."
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Saving Huygens More

Saving Huygens

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  • RTFM is the fix? (Score:5, Funny)

    by Kenja ( 541830 ) on Friday October 22, 2004 @12:13PM (#10598965)
    So wait, reading the article will fix the Cassini probe?

    • Not quite (Score:5, Funny)

      by palad1 ( 571416 ) on Friday October 22, 2004 @12:13PM (#10598972)
      RTFA will fix the probe.
    • It's like that damn Peter Pan play when you were a kid:
      "If we all clap hard enough maybe Tinkerbell will be okay..."

      We just hafta clap loud enough to be heard in space?

      Sounds doubtful to me.

      =tkk

    • Re:RTFM is the fix? (Score:4, Interesting)

      by Random_Goblin ( 781985 ) on Friday October 22, 2004 @12:45PM (#10599323)
      from TFM
      Alenia Spazio's insistence on confidentiality may have played a role in this oversight. NASA reviewers were never given the specs of the receiver..."Alenia Spazio considered JPL to be a competitor and treated the radio design as proprietary data."

      ...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.

      so in this case the problem was indeed caused by the fact they couldn't RTFM to check the supplier had done the job correctly.

      I think it is all summed up with the line "An Alenia Spazio spokeswoman said that none of the company's officials were available to comment because of a company-wide summer vacation period."

      • Re:RTFM is the fix? (Score:3, Insightful)

        by Buran ( 150348 )
        This is why spacecraft design should be "open sourced" and put up for download so that engineers everywhere can review it and point out problems.

        Contractors should be heavily punished if their designs fail -- make them pay to redesign and refly, for instance. "You can cram your agreement up your ass because we paid to buy this from you and because it's on a publicly funded spacecraft. We're posting this on the web now so stop whining."

        And why do we keep buying from Lockheed when they've fucked up so many

        • Re:RTFM is the fix? (Score:5, Informative)

          by twiddlingbits ( 707452 ) on Friday October 22, 2004 @02:18PM (#10600736)
          NASA Has an Independant Verification and Validation Center to provide technical oversight. I worked there (it's in West F'ing Virgina of all places). The folks there do a great job with what data they are given. Often to save costs, this IV&V team is not even allowed to participate in the Design Reviews, and when they are and discover issue the Project Offices sweep them under the rug. No use admitting to problems that might show someone is not thinking correctly or is not managing the project well. The theory is "Let's avoid the problems by witholding information and communication from anyone who might find a problem". Solid testing? Thats a joke too, it costs money to test things well, and who knows they might break!. Contractors will make mistakes, after all they employ humans, but the mistakes can be corrected BEFORE flight if they are found. Having an extra set of eyes, and doing extensive testing is valuable but costly. In FACT having IV&V on manned systems is the LAW since the Challenger disaster, it's just commonly disregarded at NASA for anything but ISS. Even STS has no IV&V, after all it's a "mature" system and there are no bugs left. Regardless of what you hear about NASA "changing" after Columbia it really isn't. I fully expect another STS disaster, and several more mini-disasters in unmanned systems in the near future.

      • Re:RTFM is the fix? (Score:5, Insightful)

        by drew ( 2081 ) on Friday October 22, 2004 @02:00PM (#10600321) Homepage
        In many European countries there is a month long period where everyone goes on vacation. As I understand it, pretty much the entire country except for basic service industries shuts down for a month. I don't understand the specifics, as I've never been to Europe during a vaction, but I did work on a project once with SwedenPost (the Swedish Post Office) that ended up being pushed back quite a bit because the original project schedule had us going into client QA right as the entire company took a month and a half off for vacation. And this was the Post Office!

        So I doubt that the fact that all of the company's officials were on summer vaction at the same time reflects on their abilities to design complicated hardware. It's just business as usual over there.

        And as the article points out, NASA probably could have gotten the specs if they had signed an NDA but they didn't believe they were necessary. Given that statement, it's quite possible that no one would have looked at the specs close enough to notice the problem, even if they had them.

  • The fix: **Spoiler Alert** (Score:2, Funny)

    by Anonymous Coward
    Change the cosmological constant of the universe.

  • Save yourself from RTA, the fix is: (Score:5, Funny)

    by Tibor the Hun ( 143056 ) on Friday October 22, 2004 @12:14PM (#10598983)
    reversing the polarity of the transponder...
    duh...

    • NOOO!!! (Score:2, Informative)

      by Tibor the Hun ( 143056 )
      I was trying to be funny! Don't mod me Informative! Woe to all who read the OP and consider it Informative.

      It was a reference to star trek!

      • Re:NOOO!!! (Score:3, Funny)

        by Anonymous Coward
        Given this is Slashdot I'd bet there are some that view Star Trek as absolute reality. Aparently some of them have mod points as well. *shudder*
    • Actually I would have thought that at first, but on further review it appears you would have to modulate the deflector array with an inverted tachyon pulse.

  • What is this? (Score:2, Funny)

    by Anonymous Coward
    So now /. wants us to actually... read?
    • > So now /. wants us to actually... read?

      Yeah, I mean since when have we stopped catering to the illiterate geek community? People who can't read have rights too!

  • Lots of amazing stuff (Score:5, Interesting)

    by erick99 ( 743982 ) <homerun@gmail.com> on Friday October 22, 2004 @12:14PM (#10598990)
    It is amazing that the problem with the reciever was detected. It was more amazing to read what they went through to document and present the problem. It also says something about the relationship between NASA and it's subcontractors when they can accept a receiver design and not sign a standard non-disclosure agreement so that they can see the specific design elements. If they had done so, they would have been able to see the problem before launch. However, having read the article, the complexity of the mission is such that I am possibly more amazed that more didn't go wrong.

    • May not be that simple... (Score:4, Insightful)

      by Smilodon ( 66992 ) on Friday October 22, 2004 @12:37PM (#10599223)
      This is not a simple subcontractor arrangement. It is cooperation between government agencies in different governments, each of which has private contractors working for them.

      Besides the obvious contractual nightmare this represents, there is also the issue of Export control between governments, which cannot be countermanded with a simple non-disclosure.

      IMNAL, but I work on a similar project and you need to learn some of this stuff, sadly, to get your work done. I'm hopeful this incident will help to clear up these sort of cooperation issues in the future.

      Good work in resolving this all involved! Remember Slashdotters, we explore to learn...
    • ...or reject proprietary designs alltogether, so as to make the specs available to the whole organization. The problem here was that the subcontractor didn't want JPL folks to poke at it, since they were "competitors". But that also means that the JPL folks are peers, and if those peers were interested enough in the design, those peers would have performed a peer-review, which is a central tenet of science.

      The problem is that someone willing to sign an NDA is also in a situation where you cannot compete

    • However, having read the article, the complexity of the mission is such that I am possibly more amazed that more didn't go wrong.

      The Huygens probe has yet to be deployed to Titan. Thus, it is too early tell if there are not other significant problems.
    • It also says something about the relationship between NASA and it's subcontractors when they can accept a receiver design and not sign a standard non-disclosure agreement so that they can see the specific design elements.

      Sort of. This was really an ESA project and NASA was was only assisting the them. If this was a NASA run project I'm sure they would have insited in seeing what the specs were (now weather that would have helped is a different question). I wonder if Alenia Spazio (the contractor) gave t

  • farsighted (Score:5, Funny)

    by Doc Ruby ( 173196 ) on Friday October 22, 2004 @12:16PM (#10599003) Homepage Journal
    Installing the reentry sensor upside down, ignoring the Doppler effect - this rocket science stuff is so hard, they're missing all the easy stuff.

    • Re:farsighted (Score:5, Interesting)

      by hopemafia ( 155867 ) on Friday October 22, 2004 @01:08PM (#10599554)
      It's actually fairly common...when you have a bunch of smart people working on difficult problems they tend to breeze through the easy parts, and don't necessarily double check each other's work because of "Jim has 2 PhD's...he'll get that right" syndrome.

      Reminds me of taking caculus exams...it was always something dumb like switching +/- or "1+1=3" that I got wrong...not the partial differentials.

      It just shows that no matter how smart you are, if you hurry and don't pay attention to every trivial detail you'll make mistakes.
      • reminds me of my high-school calculus exam... I did all the work correctly on my scratch paper, then incorrectly transcribed the answer onto the answer sheet.
      • too true. i had a nobel laureate as a teacher in my freshman physics course in college. brilliant man, and a great researcher, but i couldn't help being amused seeing him stumble over basic physics problems and getting stuck to the point that the class would have to point out what he was doing wrong.

  • Horizon (Score:2, Interesting)

    by Gaima ( 174551 )
    God bless good 'ole auntie.
    Saw this on Horizon yesterday evening.

    Always nice to see a simple solution.
    Now if only NASA could find a simple solution to conversions between imperial and metric, or not undoing bolts :)

    • Re:Horizon (Score:3, Interesting)

      by payndz ( 589033 )
      An informative show, even if the CG got a bit repetitive (they used the same clip looking down from Saturn's pole before sweeping into the rings six or seven times, and even had to start flipping the image to disguise it!)

      Anyone else notice just how much familiar movie music was in there? The sequence of Cassini being loaded into the Delta was accompanied by a track from Armageddon, a space flyby CG sequence had the 1989 Batman theme, and one of the Titan shots used the 'opening of the Ark' theme from Rai

    • Re:Horizon (Score:3, Interesting)

      by orac2 ( 88688 )
      But if I may point out, to all those BBC viewers yawning "old news", this story was published by us on October 1st. (I actually submitted it at the time but the /. Gods rejected it).

      Disclaimer -- I work for IEEE Spectrum.
      • I don't remember when I got the current Spectrum, but this is indeed old news.

        [I don't work for IEEE Spectrum]

  • Old news (Score:4, Informative)

    by Timesprout ( 579035 ) on Friday October 22, 2004 @12:16PM (#10599008)
    The problem was discovered years ago, took 6 months to investigate and nearly 2 years to resolve. The BBC told us all about it with nice graphics the other night.

    • Re:Old news (Score:3, Interesting)

      by orac2 ( 88688 )
      That's nice. Did they actually explain how the Doppler shift affected the BPS coding used in the Huygen's telemetry, or describe how the problem was missed, or tell the story of Boris Smeds pushed through his test and ended up modifying it on the fly? And does every reader of IEEE Spectrum get the BBC on their TV? (hint, Spectrum has a global circulation)

      -- disclaimer, I edited (and did some reporting for) this story.

  • classic (Score:5, Funny)

    by theMerovingian ( 722983 ) on Friday October 22, 2004 @12:17PM (#10599013) Journal

    "We have a technical term for what went wrong here," one of Huygens's principal investigators, John Zarnecki of Britain's Open University, would later explain to reporters: "It's called a cock-up."

    We Americans speak English, but this is proof positive that the British have had much more time to master the use of it :)

    • Re:classic (Score:2, Funny)

      by Anonymous Coward
      "We have a technical term for what went wrong here," one of Huygens's principal investigators, John Zarnecki of Britain's Open University, would later explain to reporters: "It's called a cock-up."

      We Americans speak English, but this is proof positive that the British have had much more time to master the use of it :)

      Of course we would tend to think that a "cock up" might very well be a good thing. ;)

  • We have a technical term for it (Score:5, Informative)

    by RealAlaskan ( 576404 ) on Friday October 22, 2004 @12:18PM (#10599031) Homepage Journal
    "We have a technical term for what went wrong here," one of Huygens's principal investigators, John Zarnecki of Britain's Open University, would later explain to reporters: "It's called a cock-up."

    Oooooh! I love that technical jargon.

    Spoiler Warning:

    ... the Cassini team crafted a response plan that centered on reducing the Doppler shift sufficiently to keep the data signal within the recognition range of the receiver. They accomplished this trick by altering the planned trajectory of Cassini.

    Now you know how they fixed it, so no need to read the article.

    • Now you know how they fixed it, so no need to read the article.

      Like that would ever happen on Slashdot anyway...

    • Now you know how they fixed it, so no need to read the article.

      Thank you for the summary! I tried to RTFA, but I got tired of the tedious dumbed-down human interest after the first thousand words of breathless "Could the mission be saved, or was it too late?" tosh that these journalists always seem to feel they have to pad their word counts with.

      I guess I should be glad they hadn't quite managed to turn it into One Man's Struggle Against the Establishment. And if the guy had got divorced or lost a chil

  • Saving Pvt Huygens (Score:3, Funny)

    by nounderscores ( 246517 ) on Friday October 22, 2004 @12:24PM (#10599105)
    This time the probe is the mission.

    "I tell you this Huygens had better develop a better theory of light or something..." -Cpt Miller

    "Nasa has lost so many probes. We can't let them lose any more. We have to bring the data back." - Boris Smeds

  • I could have helped out with this (Score:5, Funny)

    by kalpol ( 714519 ) on Friday October 22, 2004 @12:30PM (#10599159)
    I drove a Fiat for years. I could have told them an Italian radio wasn't gonna work. :)

  • Long vacation. (Score:4, Funny)

    by RobertB-DC ( 622190 ) * on Friday October 22, 2004 @12:38PM (#10599245) Homepage Journal
    [NASA's] Horttor never got an explanation of why Alenia Spazio's telemetry system was built with a timing system that couldn't accommodate the Doppler shift in Huygens's telemetry. "It is a design feature of another application in Earth orbit, and they just reused it," he told Spectrum, adding, "I don't know why anyone would ever want to build it that way." (An Alenia Spazio spokeswoman said that none of the company's officials were available to comment because of a company-wide summer vacation period.)

    Anyone think that the "company-wide summer vacation" may extend a little longer than originally expected?

    "Hey, Tony! Glad to hear you ready for work. But why don't you go ahead and stay in Verona another month or two? Check out this web site [monster.it] while you're there. Ciao!"
  • I was expecting something involving quantum fluctuations, baryon sweeps and tachyon beams.
    • I know what you mean. I was expecting something about reprogramming Cassini or Huygens or both. But then I read:

      ...the firmware could not be altered after launch.

      What? A $300M mission, and there's no provision for firmware upgrades? Even my $40 wireless hub can get firmware upgrades. Oh, wait: "Do NOT upgrade firmware on any D-Link product over a wireless connection. Failure of the device may result. Use only hard-wired network connections."

      So I guess they'd have had to run a billion-mile cab

      • So I guess they'd have had to run a billion-mile cable first. Line noise would be a bitch, wouldn't it?

        Who cares about line noise, I want to see the whiplash at the end of the cable when I tap it on this end. Whip that probe!

        -Adam

  • Clever Solution (Score:5, Informative)

    by SparksMcGee ( 812424 ) on Friday October 22, 2004 @12:45PM (#10599313)
    It looks like the relative velocity of Cassini to Huygens actually *was* high enough to lend a singificant Doppler shift, so correspondingly the data rate was massively compressed--like the frequency of a racecar coming towards you getting higher and higher, except in this case its bitrate instead of sound. The antenna was only designed to "listen" for a fairly static bitrate --like if once the car got close enough and the sound frequency high enough you just stopped hearing it. So instead they're altering the flightpaths so that Cassini is now far enough away from Huygens that the broadcast vector is mostly perpendicular, with minimal Doppler shift -- think about standing very far away from the racetrack instead of right in front of the car. The total distance between you and the car changes by much less, so you hear more of a constant hum than a higher and higher frequency, analogous to the drone of a jet plane passing far overhead. Because the Doppler shift is minimal, the antenna can now receive data at a nearly constant bitrate it can handle. Very nicely done.
    • It is so nice when someone actually bothers to read the bloody article. Thank you!

      Disclaimer: I edited this story for IEEE Spectrum

    • Re:Clever Solution (Score:3, Insightful)

      by mefus ( 34481 )
      So instead they're altering the flightpaths so that Cassini is now far enough away from Huygens that the broadcast vector is mostly perpendicular, with minimal Doppler shift -- think about standing very far away from the racetrack instead of right in front of the car.

      Today on slashdot I learned that angle of incidence is a function of distance. Thanks for the "informative" post.

  • SDR (Score:5, Informative)

    by wowbagger ( 69688 ) on Friday October 22, 2004 @12:46PM (#10599326) Homepage Journal
    What I find hard to beleive is that the data slicer for the radio was not a chunk of code running on a processor, rather than a hardwired circuit.

    I do SDR (Software Defined Radio) for a living - doing a data slicer like this isn't very hard at all. Why they couldn't just reprogram the slicer to take into account the bit timing shift - or better still, why weren't they resyncing on the zero crossings of the signal so they could deal with bit timing errors automatically?

    Hell, for that matter why don't they have an option to route the recovered signal verbatim to the main transmitter and send that to earth - and do the signal processing here? NASA *used* to have the philosophy of "all the bits to earth" - the wouldn't even use lossless data compression lest the signal be corrupted and unrecoverable.

    • Re:SDR (Score:3, Informative)

      by Anonymous Coward
      Why they couldn't just reprogram the slicer to take into account the bit timing

      because as the article said, the firmware was not designed for being reflashed remotely.

    • RTFA (Score:3, Informative)

      by scribblej ( 195445 )
      Is *IS* a "software" radio and not hardware. It's implemented in "firmware" and they say they could have changed it easily, except there's apparently no way to do so after launch.

      The problem is they didn't find this problem until AFTER launch. good timing, right?
      • And that is my point - why did they make it so that they could not reflash it in flight?

        And again, why did they not design the slicer to resync on zero crossings, which would have prevented the problem in the first place?
        • The software was from a design used in earth sats, the ability to deal with doppler shift like that was not part of its design spec (I wonder if NASA got ripped of because they probably paid for a custom radio module and they got an off-the-shelf design).

          There were lots of ways the receiver could have been done that would have been better, but it wasn't done that way, and they didnt' have the code, nor any way to fix it remotely anyway.

          Faster, Better, Cheaper. Pick two.
        • And again, why did they not design the slicer to resync on zero crossings

          It's a BPSK receiver, so the zero crossings are the data. I would think the decoder would look like a fast PLL whose center frequency corresponds to the nominal data rate, with enough locking range to handle Doppler-induced variations. Guess there was little or no locking range after all.

    • Re:SDR (Score:2, Interesting)

      by bware ( 148533 )

      Were you doing SDR in 1997 when Cassini was launched? Were you doing it in 1987 when Cassini was being designed?

      All the bits don't come to earth because Cassini doesn't have continuous data transmission to the Earth. That would be extremely expensive. DSN time is charged out the wazoo. I don't know Cassini specs, but most missions plan on recording data and shipping it back to Earth when DSN time is allocated. It isn't continous. DSN has other things to do.

      You want to send the raw analog signals ("v
      • Yes, I *was* doing SDR in 1997. I was in college in 1987, but this sort of demodulation has been done since the 1960's.

        The fact that the slicer couldn't be reflashed in flight is just plain stupid - and that is my point.

        And as for sending the raw signals - I did not say "make that the only option" - I said "why is that NOT an option". The whole thing about designing spacecraft is to have as much flexibility as possible so that WHEN the unexpected happens, you have a shot at a work-around.

      • Re:SDR (Score:4, Informative)

        by twiddlingbits ( 707452 ) on Friday October 22, 2004 @02:26PM (#10600898)
        DSN is saturated and time slices are VERY hard to get. It needs to be upgraded, but there is not any money. NASA will spend 10's of millions on a probe but won't spend any on the data network to get the probe's data to the ground. In part, due to the saturation of DSN, most missions now have to have an on-board data recorder that holds anywhere from 24 hours to 7 days of data for compressed delivery when a slot is open. That adds costs and weight to every mission.

    • Re:SDR (Score:5, Informative)

      by Anonymous Coward on Friday October 22, 2004 @01:25PM (#10599758)
      The signal strength is very weak. We'll be using the 100 meter Greenbanks telescope, as well as the VLA, Parkes and Mauna Kea radio telescopes to record the signal on the ground, but the primary plan is still the Cassini orbiter.

      This isn't the only screw-up for Alenia this mission. Look for articles involving the Ka Band Translator if you're interested. You may not find many, it hasn't been covered very publicly. Basically, we can no longer send a Ka band uplink to the spacecraft becasue the Alenia built receiver broke. See Paragraph 10 here [spinics.net]

    • Re:SDR (Score:2)

      by orac2 ( 88688 )
      why don't they have an option to route the recovered signal verbatim to the main transmitter and send that to earth

      The big dish they use to transmit to Earth is also the dish that will be used to pick up Huygen's signal -- it can't be pointing in two places at once.

  • Proprietary (Score:3, Insightful)

    by Eryximachus ( 819128 ) on Friday October 22, 2004 @12:46PM (#10599328)
    A shining example of the promblems with proprietary design. No one can see what's wrong with it without expending a huge amount of effort. I'm just glad someone did decide to spend the effort.
  • The problem - Doppler effect. The fix: go read the article.

    The problem was a 'undetectable' flaw in the transceiver the solution exploited the Doppler effect, by slowing down the satellite they were able to change the way in which the receiver received the transmissions and recover all the data.

  • Slashdot needs a 'HERO' tag (Score:5, Interesting)

    by mcrbids ( 148650 ) on Friday October 22, 2004 @12:53PM (#10599391) Journal
    While slashdot has category icons, it really REALLY needs a "hero" tag, like you'd see on Fark.

    This engineer that found the problem and rallied against opposition to see that this gets fixed is, in my opinion, a total hero. The world would be a much better place if more people like him were around!
  • And this, my friends, is an example of a great hack (and, by extention, a great hacker).

    Kudos. A relatively unknown engineer suddenly earned a great deal of respect from me.

  • Great work by Smeds. (Score:4, Interesting)

    by francisew ( 611090 ) on Friday October 22, 2004 @04:22PM (#10602875) Homepage

    Boris Smeds did a great job in replacing lots of expensive tests with a series of trivial, yet critical tests.

    Why weren't simple tests like these used while the spacecraft was on the ground?

    These are obvious problems. When you take a transmitter and throw it into a planetary descent, this is what should be expected.

    It is shocking to me that a transceiver pair isn't tested by the team assembling the spacecraft before launch!

    If it can be tested in 2 days when it's in space, 48 light-speed minutes away, why can't it be tested on the ground, fully assembled?

    Engineering isn't a science, but I expect that engineers desigining projects like this should be using thorough unbiased scientific testing, not only thorough design.

    If they slip up like this in non-destructive tests, one has to wonder about how tests on the resistance to physical damage are carried out?

    Do they simply make assumptions that all nuts & bolts are manufactured to spec? Do they assume that all parts will withstand the forces that they are requesting in spec sheets?

    How can a cost of hundreds of millions of dollars be justified in creating such craft, when basic, inexpensive testing isn't being carried out? If the test would cost 30,000$ (a few days of well-paid outside experts time, plus expenses and travel), as a critical portion of a 300,000,000$ mission, how is it not done?

    The only agreement that should be accepted by an agency purchasing a part is that they won't use the specifications of that part to replicate exactly the same device. I'm sure that they paid a high premium for the transceiver. Why wouldn't they have access to the documentation and spec sheets? This use of NDA's is dangerous.

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