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Originally Posted by Aerich
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Originally Posted by Jerry
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Originally Posted by Aerich
If I were designing the circuit and/or code which performs impact sensing using ACC-E data, I'd surely include a register or variable to store the current time when my system decided that an impact had happened. Cheap, easy to do, and an obviously desirable feature. (And yes, I can design that kind of thing, though I have never worked on space hardware, alas.)
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Never underestimate the ignorance of experts - The block diagram shows the signal being stuffed into a buffer, but not a time stamp. There is no mention in the text of a time stamp, even though there were triple-redundant timers in the system. |
The document is a very general overview of the system, not a detailed design specification. It does not surprise me that such details were left out of it.
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Originally Posted by jerry
I get to assume that there was not a time stamp because it is the only way I can explain the data.
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Why should you get to assume that? I don't see any justification for it. |
If you were designing the system, wouldn't you make sure that the receiver was capable of receiving the signal within the expected bandwidth? Wouldn't you include in the program a command to turn the receiver on?
In a court of law, if the defense can present a scenario that is just as plausible as the government's case, but exhonerates the defendant, the judge must give the defenses reasoning equal weight, and throw the case out.
I think it is plausible that there were multiple oversights in the design of the electronics and soft logic in the Huygens system. Too many cooks.
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Originally Posted by Aerich
Are you willing to concede that you're wrong if the tilt sensor data does not match your descent theory?
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Tough question. I cannot completely rule out a scene where the probe slowly drifted at low altitudes for more than an hour - although we have been told that the timer function would have jettisoned the 8 m parachute in twenty minutes, regardless of how confusing the accelerometer data is.
If Huygens landed on a rock and sat and wobbled, it would be obvious in the images. I don't see how the tilt sensor could indicate any activity after more than 25 minutes...
But let's look at all the sensors - I would hate to throw out a perfectly good theory, just because the tilt indicator wasn't screwed down properly - I've played pinball games that would tilt if you breathed too heavy.
The temperature sensors are on the 'top hat', (which is really on the bottom) of the probe. As soon as the heat shield is popped off, the probes are exposed directly to the Titan atmosphere- So there is no way on Titan that temperature readings more than ~15 minutes into the mission should have been reported at 25C. I think this is pretty darn good evidence that the heat shield was still in place, long after it should have fallen on a completely different trajectory.