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Originally Posted by PeteB
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Originally Posted by jerry
My interpretation is clearly speculative
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snip! The horizontal scale was given in clock time onboard the probe (as CET): 2 hours and 27 minutes on the parachutes and about 1 hour and 10 minutes on the surface. She said that those times were taken from the probe's timer/clock, not from the nominal expected times from the pre-entry mission profile.
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Thank you, this is the type of verification I have been looking for all along! It identifies the source, both instrumentally and the scientist.
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Originally Posted by PeteB
Your imagined timeline for the entry is complete bunk.
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No it is not. Look what would have happened if I am right:
Huygens software was designed to optimize the data stream to Cassini, keeping the buffers full of the data considered most important in each altitude segment. Huygens only had a lookup table to determine the altitude above ~ 30km, so if the descent through the upper atmosphere was much faster than expected, the altitude vrs. Time table is meaningless.
Below ~40 km, Huygens had both the time-at-altitude table and the radar data to consider, but a sanity check was run on the radar data, and if it didn’t pass, the look-up table was still used to decide what altitude the probe was at - If the gravimetric force was greater than expected, the accelerometers may have still been recording accelerations above the expected gravimetric force, so the probe would have assumed it was still falling, even though it was sitting on the ground.
The software would not have even polled the penetrometer data until the time-at-altitude chart was complete. Once it did, it would then send the landing report to Cassini, more than an hour after the landing actually occurred!
Whether this scenario is possible or not depends upon which data Huygens was using to determine altitude below 40 km – the radar data, or the time-at-altitude data. There was a single bit flag sent with the report saying which was used (the radar data was also duplicated in the housekeeping report). Elias has told us that the accelerometer and Doppler Radar reconstruction only differed slightly from the ‘origin descent profile’, but what data was used in the original construction below 40 km? Radar, or the look-up table?