Why 20"?

Post #121,245 by Another Scott 10/14/03 10:39:15 PM Reply	Why 20"? Why did you pick 20" in your example? That's probably on the small end of mirror sizes for this application. The Hubble Space telescope's mirror is [link\|http://www.coseti.org/9008-065.htm\|2.4 m in diameter]. It was probably exceeded in resolution by several [link\|http://users.ox.ac.uk/~daveh/Space/Military/milspace_recon.html\|military satellites]. That page claims resolutions as small as less than 10 cm. [link\|http://www.digitalglobe.com/products/standard.shtml\|Digital Globe] is claiming that they have 60 cm/2 foot resolution from their [link\|http://spaceflightnow.com/delta/d288/011015quickbird.html\|Quickbird] satellite. It claims to be the highest resolution commercial imagery satellite available. Your points about atmospheric turbulence, etc., are well taken, though there are [link\|http://z.iwethey.org/forums/render/content/show?contentid=80136\|ways] to get around some of them. ;-) Being able to count toe hairs from 150 miles up probably isn't feasible anytime soon though, as you rightly point out. :-) Cheers, Scott.
Post #121,246 by deSitter 10/14/03 10:50:23 PM Reply	Re: Why 20"? 1) 10 cm = 4 inches :) 2) The Hubble would not work if pointed at Earth. It's extremely sensitive to infrared radiation. Plus differential heating would ruin the performance. 3) 20in is a big telescope. I'm assuming military satellites use Maksutov-type closed-end optics. Putting up, say, a 40in telescope would be an enormous undertaking on the level of the Hubble scope. I doubt a corrector plate that big, that did not go geometrically apeshit when moving in and out of the Earth's shadow, could be made. -drl
Post #121,251 by ben_tilly 10/14/03 11:43:49 PM Reply	So don't go in the Earth's shadow A polar orbit covers the whole Earth eventually, and keeps you in a constant orientation vs the Sun. Cheers, Ben "good ideas and bad code build communities, the other three combinations do not" - [link\|http://archives.real-time.com/pipermail/cocoon-devel/2000-October/003023.html\|Stefano Mazzocchi]
Post #121,269 by drewk 10/15/03 8:54:15 AM Reply	Is that a technical term? ... go geometrically apeshit ... === Implicitly condoning stupidity since 2001.

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