Saturn Experiment Might Be Salvageable 27
komissar writes "The Seattle Times has a recent update on possible salvaging of the Atkinson Saturn experiment.
With some work, the data may be recoverable."
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Saturn Experiment Might Be Salvageable
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"Hello again, Peabody here..." -- Mister Peabody
Great quote... (Score:3, Insightful)
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)
Re:Great quote... (Score:2, Informative)
Re:Great quote... (Score:3, Informative)
Nothing new (Score:5, Informative)
Computational efforts required on Earth only? (Score:4, Interesting)
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.
Re:Computational efforts required on Earth only? (Score:1)
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
I disagree with your reading of TFA (Score:3, Interesting)
I
Re:I disagree with your reading of TFA (Score:3, Funny)
Claims are unsubstantiated.
Source?
--MQ
Re:I disagree with your reading of TFA (Score:2)
Re:I disagree with your reading of TFA (Score:2)
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
Re:I disagree with your reading of TFA (Score:2)
Binary phase-shift keying (Score:1)
I find it a little confusing too, but as described in last year's IEEE Spectrum article on the Cassini relay doppler shift problem [ieee.org], the radio link from Huygens used neither frequency nor amplitude modulation, but rather phase modulation:
This is not clear.. (Score:2, Interesting)
Its an important difference - if they can retrieve the A-Channel data, they can re-generate the lost picture data from that channel too..
Re:This is not clear.. (Score:1)
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.
Ambiguity (Score:1)
how did they know to start listening? (Score:3, Interesting)
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.
They were already listening anyway (Score:1)
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
Why only one chance at transmit? (Score:4, Interesting)
Re:Why only one chance at transmit? (Score:1)
Re:Why only one chance at transmit? (Score:1)
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.