[Beowulf] Re: blackbox on Mars?
gdjacobs at gmail.com
Mon Oct 30 23:26:22 EST 2006
Jim Lux wrote:
> At 02:23 PM 10/30/2006, Geoff Jacobs wrote:
>> Jim Lux wrote:
>> > reduce the variance. Something else to do with that Beowulf sitting in
>> > your garage..
>> I believe these techniques require multiple, short exposure samples.
>> Apparently, KH-12s have a capability for real time video. I expect the
>> frame rate from such would make multi-sampling a difficult noise
>> reduction method to apply.
> See, e.g., http://citseer.ist.psu.edu/95070.html
> David Tyler,"PARSEC...", We describe a speckle imaging reconstruction
> code written for very fast image reconstruction on a parallel computing
> platform such as the IBM SP2. We describe the algorithms used for all
> stages of image reconstruction and present results of a sensitivity
> study using data obtained with the Maui Space Surveillance Site 1.6-m
> If that isn't a cluster app.....
I was mulling the exposure time required to achieve acceptable SNR, as
well as the number of samples per frame, and wondering whether the
instrument could collect enough data to assemble a video stream with
acceptable frame rate.
>> IR imagery is one thing to think about. Radar is another. X band radar
>> > (9-10 GHz) easily gives you 3cm sorts of resolution, especially with
>> > processing.
>> IR imagery does allow remote sensing at night, but it is affected by
>> weather. Also, IR typically has less resolution.
>> Radar allows all-weather remote sensing. Radar antennas are more easily
>> compacted for launch, too. However, you won't find Joe Taliban humping
>> the Hindu Kush with SAR (unless you can image his Kalishnakov).
> Sure you can, if you know where to look. The real challenge is
> separating the slow moving human from the ground clutter. Humans make a
> fine radar target (being big jelly bags with high dielectric constant,
> they have a fairly decent RCS). Could one resolve individual features
> like fingers and toes? Might be a bit tricky. Track a moving car as RGB
> asked? Not a problem. Again, the challenge is getting suitable
> coverage.. you want the angle of incidence to be something other than
Computers can track differentials in an image fairly easily. I don't
think doppler wouldn't be necessary to cull an image.
However, I gather an AESA radar is fairly adaptable, so the operator can
choose whichever imaging mode is appropriate on a satellite so equipped.
> (so you have some doppler to help remove clutter), but that
> implies low satellite height, which means you need lots of them for 24/7
Satellites as surveillance instruments have always had the disadvantage
of obeying predictable schedules with very large holes. At $2B a piece,
top of the line kit like the KH-12 or Lacrosse will never be available
in numbers the Pentagon would like.
Mass manufacturing satellites with somewhat less resolution, but in
greater numbers, would be an interesting solution, and probably
sufficient if you're just counting tanks and airplanes and don't need
the extra resolution.
> Check out Discoverer II or "Space Based Radar"
I found a paper published by Toyota(!) which investigates rcs of a human
at 76ghz. Interesting stuff.
Unfortunately, the DARPA site is not playing nice for me today. However,
I found this.
Among other things, wearing wool gives you a -20 dB cut at this
frequency. Of course, it's easy to overcome such problems by simply
pounding through more power.
Geoffrey D. Jacobs
Go to the Chinese Restaurant,
Order the Special
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