Jeff Liebermann wrote:
On Fri, 31 Oct 2008 16:27:47 -0400, "Ed Cregger"
wrote:

Perhaps someone can answer a question or two about synthetic aperture radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K

As others have mentioned, that's not synthetic aperture radar. See
the article at:
http://en.wikipedia.org/wiki/Synthetic_aperture_radar
for explanations and references. Note that either the target or the
radar has to be moving for SAR to work. A mess of small transmitters,
scattered over a wide area, will also work. A rotating radar antenna
(phased array, bedspring, or dish) will not work.

One example is the SRTM (Shuttle Radar Topography Mission), which used
interferometry and a synthetic aperture radar to map the planet. In
this case, the shuttle was moving and the ground was relatively
motionless.
http://fas.org/irp/program/collect/ifsar.htm
http://www2.jpl.nasa.gov/srtm/
Since there was only one space shuttle in orbit, the antenna must both
xmit and receive.


Not precisely true in the case of InSAR.. One transmitter, two
receivers. A Tx and Rx can share, but the second receiver needs its own
antenna. (Modern phased arrays can segment a long array into two receive
arrays to do InSAR, as well).