Quote:
|
Originally Posted by Jerry
Quote:
|
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.)
|
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.
Quote:
|
I get to assume that there was not a time stamp because it is the only way I can explain the data.
|
Why should you get to assume that? I don't see any justification for it.
Quote:
Quote:
|
But aside from all that, your basic story (that impact happened early, and noone on the Huygens team has the slightest clue) borders on the ludicrous. The table on page 193 (PDF page 17) shows that the internal accelerometer (ACC-I) and tilt (TIL) sensors are both sampled continuously throughout the portions of the descent where you claim an unexpected impact happened. It strikes me as unlikely in the extreme that the Huygens scientists could fail to notice an impact event on these sensors. And they'd know when it happened too.
|
The ACC-I accelerometer data was only stored a sample rate of 1cps during the descent portion of the mission (modes 1-3). If I am correct, yes there may be a small blip in this data at 20 minutes, just seconds after the 3 meter parachute is deployed. That blip could easily be missed.
The tilt meter is another story: If I am correct, it should display a constant value for the last ~hour of the aerial descent, and it should be the same as any tilt recorded after landing. This is a very good - perhaps the best - test of my hypothesis.
|
Are you willing to concede that you're wrong if the tilt sensor data does not match your descent theory?
Quote:
|
Is this why the Descent profiling team characterized the descent after the tropopause as being surprisingly calm? Is this why they find the optical images so confusing?
|
No. They said surprisingly calm, not stopped altogether. (Which would be quite obvious on the tilt sensor. Just read a document which said it has 0.5 degree accuracy. With that level of accuracy it ought to be quite capable of discriminating flight from rest on the ground.)
Quote:
|
It is clear from the design of the mission no one imagined anything more or less than perfectly Newtonian gravimetric forces. Not even dark matter.
|
Why should they have imagined crazy theories of gravity which match no known data? We've got a pretty long history of navigating successfully in space using Newtonian physics (which we KNOW is incorrect, but we also know it's correct enough for interplanetary flight purposes).
(For that matter (ahem), why bring in dark matter? AFAIK, dark matter theories still have gravity working the same way. They just posit matter which we haven't observed to account for the behavior of the known universe. So far as I know, no part of dark matter theory would predict an impact on the navigation of spacecraft like Cassini or Huygens.)