Article View: sci.space
Article #7871Re: satellites
From: Phil R. Karn
Date: Tue, 12 Jan 1988 19:20
Date: Tue, 12 Jan 1988 19:20
19 lines
1443 bytes
1443 bytes
> In fact, it is possible to get better than the diffraction limit, as synthetic > aperature radars have shown. Take several images from different points,(from > a satelite, easily done by just taking a few sequential pictures, since the > stelite is moving) and image-process your little brains out. Aperture synthesis doesn't "get better than the diffraction limit", it decreases the diffraction limit by building a system with a very large effective aperture. It's like having a telescope with a very large virtual mirror where only small portions of the signal gathering area is actually "filled in". You can get extremely high resolution images if you *simultaneously* photograph the same target from two or more widely separated satellites, and then *coherently* add the two images with an accuracy on the order of a small fraction of a wavelength. This is entirely practical at radio wavelengths (VLBI and SAR being two examples), but at optical wavelengths? Good luck! Phil
Technical Details
Message-ID:
<1705@faline.bellcore.com>Path:
arc1-ca.pugleaf.net!utzoo!linus!husc6!hao!gatech!rutgers!bellcore!faline!karnReferences:
<873@uop.edu> <2166@umd5.umd.edu> <4910@well.UUCP> <1952@netsys.UUCP> <7169@apple.UUCP>Show Full Headers
Complete Article Headers
Path: arc1-ca.pugleaf.net!utzoo!linus!husc6!hao!gatech!rutgers!bellcore!faline!karn From: karn@faline.bellcore.com (Phil R. Karn) Newsgroups: sci.space,sci.crypt Subject: Re: satellites Summary: synthetic aperture radars Message-ID: <1705@faline.bellcore.com> Date: 12 Jan 88 19:20:10 GMT References: <873@uop.edu> <2166@umd5.umd.edu> <4910@well.UUCP> <1952@netsys.UUCP> <7169@apple.UUCP> Organization: Bell Communications Research, Inc Lines: 19