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Saturn Experiment Might Be Salvageable

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  • Great quote... (Score:3, Insightful)

    by keiferb (267153) on Monday January 24, 2005 @10:58AM (#11455310) Homepage
    "I think right now the key lesson is this -- if you're looking for a job with instant and guaranteed success, this isn't it."

    That's from the professor in charge. On the plus side, he'll never forget to turn on one of his experiements ever again. =) Seriously, though, it's great to hear that the data may not be lost.
    • Re:Great quote... (Score:2, Informative)

      by QMO (836285)
      I couldn't see where it said that it was Atkinson that forgot. It seemed to give the impression that someone else was supposed to have done it, but it didn't really say.
      • On Thursday, Idaho scientist David Atkinson said that someone failed to turn on a radio receiver for the instrument he needed to measure the winds on Saturn's largest moon.
    • It was ESA's fault (no one is saying exactly whose fault in ESA). They created the command sequences for the Casssini/Huygens decent. They missed flipping the bit to turning on one of the two receivers. How can you forget something so important? NASA/JPL/ESA did this as a "joint" venture, so ESA had that responsibility for the Cassini programming at that point in the mission.
  • Nothing new (Score:5, Informative)

    by Frans Faase (648933) on Monday January 24, 2005 @11:45AM (#11455840) Homepage
    Sorry, to say, but the article referenced does not give any new information. The data is lost and an attempt is being made to reconstruct the path of the huygens probe using the doppler shift of the signal picked up by several radio telescopes on earth. This require huge computational efforts which can take several months to be completed.
    • by Anders Andersson (863) on Monday January 24, 2005 @01:40PM (#11457425) Homepage

      I thought they were planning to use the radio telescopes for this (reconstructing the path of the probe) long before they learned that the Channel A receiver wasn't going to be operational. Or, what was that Very Long Baseline Interferometry experiment meant for? Merely detecting the presence of a signal?

      I suppose that one advantage of doing the same measurements via two receivers (one on Earth, the other on Cassini) would be the ability to reconstruct the path in two dimensions, thereby learning not only how fast the probe travelled, but in what direction (sideways or down).

      I guess most of that computational effort may be to properly extract the true signal from all the other noise they probably recorded, much like the SETI@Home project does in a distributed fashion. However, no amount of computation can properly compensate for the loss of a receiver listening from a different position, if that's indeed what the receiver onboard Cassini was meant to do. Even if they had a dozen radio telescopes on Earth listening simultaneously, they would all detect the same doppler shift, telling them essentially nothing but the speed of Huygens relative to Earth only. As it was close to mid-day where Huygens landed on Titan, the Sun (and Earth) were close to zenith, and we would primarily be measuring descent speed, not lateral speed.

      Has anybody seen a scientific explanation of the details of the doppler wind experiment, such as what measurements the Channel A receiver was supposed to perform and how it would deliver its results to Earth? I'm pretty sure three hours of analog recording of a high-frequency carrier wave would constitute way too much raw data to transmit to Earth for later analysis, so I assume some processing must be performed already onboard Cassini. If so, performing the same process for the signal received directly via the radio telescopes shouldn't take considerably longer time, once it has been properly extracted from the noise.

      • Ah, I now realize this is exactly what interferometry is about, detecting the same signal with multiple receivers and seeing how they differ in doppler shift. Even the Earth doesn't provide that much of an angle as seen from Titan, so I admit it would be an achievement if they managed to reconstruct the path based on the data they got.

        Still, I guess the ability to measure such slight differences in doppler shift would depend more on the sensitivity of the receivers, than on computational power. They do nee

    • The head of the space probe mission to Titan said today that much of the data from a botched experiment designed by a University of Idaho professor was recovered by radio telescopes on Earth...Idaho scientist David Atkinson said that someone failed to turn on a radio receiver for the instrument he needed to measure the winds on Saturn's largest moon. Because of that error, data transmitted by the gear on the Huygens lander was not received by the Saturn-orbiting Cassini spacecraft for relay to Earth.

      I

      • The signal is extremely weak (the output was only something like 10 watt, similar to a mobile phone). As I understood it, they will only be able to reconstruct the carrier signal, and not be able to retrieve the actual data sent on that carrier signal. They are going to use frequency variations in the carrier signal to reconstruct the path of the probe. (These frequency variations are refered to as the Doppler effect.) The huygens probe at a set of detectors (some of them also using doppler effects) to meas
        • That doesn't make sense to me. Are you saying that the modulation of the carrier (for the data) was weaker than the dopler effect? That seems nutty. If it's true, how were they expecting to recover the data in the first place?

          I mean, think about it--both the data and the dopler effect are going to show up as variations in the frequency of the carrier wave (or, if you prefer, in a change in the amplitude of the signals received at frequencies near the nominal carrier frequency). From the point of view o

  • This is not clear.. (Score:2, Interesting)

    by adeyadey (678765)
    Does anyone know if they are trying to actually retrieve the A-channel data, or are they just analysing the carrier for dopler-shift to get the data for this experiment?

    Its an important difference - if they can retrieve the A-Channel data, they can re-generate the lost picture data from that channel too..
    • Its an important difference - if they can retrieve the A-Channel data, they can re-generate the lost picture data from that channel too..

      If I am not mistaken, the images were compressed (JPEG-like) when transmitted. Compressed images tend to be very sensative to missing portions. I think they would need a pretty clean signal to extract decent images, and I doubt they have that. You can probably get doppler info from choppy signals, but not compressed images.
  • See, that's the problem. "Someone" forgot to flip the bit. Makes it sound like they weren't sure who was supposed to do it. If the person who was supposed to turn the experiment on had only KNOWN that they were supposed to turn it on, this probably would have been done.
  • by menscher (597856) <menscher+slashdot&uiuc,edu> on Monday January 24, 2005 @04:58PM (#11460449) Homepage Journal
    Silly question, but at what point did they realize there was a problem? If they didn't find out there was a problem until after failing to receive channel A data from the orbiter, then the radio waves from the probe would have already passed the Earth also.

    Did they somehow know that they'd forgotten to flip the switch before any data was transmitted?

    Or maybe the transmit time was several days, and they only missed the first few hours?

    Just trying to make sense out of this, since the journalists obviously don't have a clue. Hopefully someone who worked on the project can respond.

    • If they didn't find out there was a problem until after failing to receive channel A data from the orbiter, then the radio waves from the probe would have already passed the Earth also.

      They learned that there was a problem when the Cassini relay transmission came in loud and clear at ESA, but with Channel B data only. At that time there would have been no point in enabling the Channel A receiver, as Cassini had already lost contact with Huygens.

      The radio telescopes listened to the signal from Huygens di

  • by Vellmont (569020) on Monday January 24, 2005 @06:59PM (#11462066)
    I tried a few days ago, but couldn't find much information on the design of the Huygens probe. One thing I don't quite understand is why they only planned to transmit the data once, then leave Huygens for dead? Is it because of the extreme cold of the planet and they couldn't prove enough heating + insulation, or were there other factors involved? The vaccum of space is rather cold too, but electronics seem to work OK.
    • My understanding from a radio interview was that the lander was battery powered and that it was a power issue.
      • My understanding from a radio interview was that the lander was battery powered and that it was a power issue.

        Further, Cassini only passes by Titan roughly about once every 2 months. The battery is not going to last for 2 months, and the probe may have sank in mud by then anyhow.

        Probably the only way to have power for 2+ months is to use the contraversial "nuke packs" rather than chemical batteries. There is not enough sunlight to use solar power there.

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