Re: Spy Satelites

[Andy Dougherty <doughera@LAFAYETTE.EDU>]

On Mon, 13 Dec 1999, Richard Tarara wrote:

> A recently launched commercial satellite that can take hi-res photos (for
> sale) has a resolution of 3 meters.  It was openly stated in their info that
> resolutions down to a meter were possible (with unclassified equipment).

Atmospheric turbulence is also an important limiting factor.  The
resolution angle typically quoted is something like 0.5 seconds of arc for
visible light.  In some cases, adaptive optics can help bring that
resolution down closer to the diffraction limit.  There is an old (and
almost surely dated) article on adaptive optics in the April 1991 Physics
Today (pg. 50 or so).

    Andy Dougherty              doughera@lafayette.edu
    Dept. of Physics
    Lafayette College, Easton PA 18042