[Beowulf] Re: blackbox on Mars?

[Geoff Jacobs]

Jim Lux wrote:
> At 06:32 AM 10/30/2006, Jim Lux wrote:
>> At 12:45 AM 10/30/2006, Jakob Oestergaard wrote:
>>> On Fri, Oct 20, 2006 at 04:21:31PM -0400, Robert G. Brown wrote:
>>> ...
>>> ...
>>> > geosync on Earth, and if the military and weather programs have
>>> given us
>>> > nothing else, they've given us simply gangbusters orbital cameras.  I
>>> > mean who on this list hasn't gone on Google Earth yet?  Through
>>> EARTH's
>>> > atmosphere and from EARTH orbit you can see my house here:
>>> >
>>> >   35^\circ 59' 17.10"N
>>> >   78^\circ 58' 50.22"W
>>> >
>>> > At 512 feet you can clearly make out my Ford Excursion in the
>>> driveway,
>>> > see the row of cypruses along the back, see the white table on my back
>>> > deck that is about 4' across, see an azalea bush out front (next to
>>> the
>>> > sidewalk) that is about 1.5' across.  And this isn't the world's best
>>> > camera or as high resolution as they could manage, even through
>>> Earth's
>>> > soupy atmosphere.
>>>
>>> Mmm... Except... The high res images are from a plane because you can't
>>> really make out the fine details from a satellite through the earth's
>>> atmosphere.
> 
> It's true that most of the Google Earth images are aerial photos, but
> I would imagine that one can get 10s of centimeter resolution from orbit
> on Earth (assuming that clouds aren't in the way).   An old surveillance
> satellite (Corona) was doing better than 2 meter resolution in the 1970s.

Absolutely. Assume modern recon sats use a primary mirror similar in
size to the Hubble primary (both made by Perkin-Elmer). Calculating the
Rayleigh limit for an Improved Crystal satellite such as that launched
with USA 186 (Apogee 1050km, Perogee 264km) gives a max resolution of
7.9cm at 600nm and min resolution 31.5cm at 600nm. Space Imaging
typically quotes max res. of 1m with IKONOS. DigitalGlobe says 61cm in
B&W with their satellites.

I would suspect that methods for dealing with atmospheric degradation is
the secret sauce in the NROs architecture, especially WRT real-time
applications of IMGINT.

-- 
Geoffrey D. Jacobs

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