Re: [GZG] Satellite imagery

Hi,

There are several considerations when deciding where to place 
reconnaissance
satellites. This has nothing to do with technology, but just plain 
physics.

- The ability to cover the target at vertical viewing angles.

- The ability to scan the entire orbited object.

- The amount of time it takes to return to the same point on the 
orbited object.

- The limits of the observing optics (the extreme being diffraction 
limited optics.)

So, if your target is at a fixed longitude, very low latitude, and your
optics are excellent, then geosynchronous orbits make sense for this 
role.

For Earth's orbit at the extreme end of the visible spectrum (400 nm) 
you would need
a ~8.75 m diffraction limited telescope to get 2 m resolution (which is 
pretty poor.)

Maybe there is some way to PSB all these considerations (and any I've 
missed) away.
I just don't see them ;-)

Cheers,
Tony C.

On 9-Mar-06, at 12:50 PM, Eric Foley wrote:

> Well, even if satellites today aren't able to do sub 2 meter 
> photography from higher orbits, this by no means says that they 
> couldn't do it in a future where FTL travel is possible.  The 
> government obviously never releases their best satellite photography 
> publicly, but even what they have released (that probably has seen a 
> significant and deliberate drop in quality from what they have in hand

> themselves) is good enough that I personally have no doubt that 
> reading license plates from orbit is a fairly trivial accomplishment 
> for them these days.
>
> This begins to remind me of the debate about planetside weapons versus

> orbital ones, in which it was posited that in the far future 
> satellites and other low flying spacecraft wouldn't really be all that

> safe close to a well protected planet.  Hammer's Slammers posits that 
> just about anything that flies above ground tends to die in their 
> glorification of super hovertanks. I would tend to think that it 
> wouldn't be quite that extreme, but it would be an interesting 
> dynamic.
>
> E
>
> ----- Original Message ----- From: "Tony Christney" 
> <tchristney@telus.net>
> To: <gzg-l@lists.csua.berkeley.edu>
> Sent: Thursday, March 09, 2006 9:27 AM
> Subject: Re: [GZG] Re: Gzg-l Digest, Vol 11, Issue 26
>
>
>> Definitely not talking about geosynchronous satellites. Their orbits 
>> are much too
>> high to be effective at surveillance, i.e. sub 2 meter photography.
>>
>> Tony C.
>>
>> On 8-Mar-06, at 2:19 PM, Glenn Wilson wrote:
>>
>>> UAVs and satellites fulfill different functions. Also, are we 
>>> talking geosynchronous (spelling) satellites?
>>>
>>
>>
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