INVERSION OF SYNTHETIC APERTUR,E R,ADAR (SAR) - MSpace ...

and large power supply l¡ecause the along-tlack lesolution is detelminecl ì:y
the physical length of the antenna apertule in the RAR system. The size of
antenna anc{ power specification are severe constraints if an imaging raclar- is
to be operatecl on a satellite or other spaceclaft, SAR, in which the alongtrack
lesolution is detelminecl by signal plocessing equivalent to a longel
sylthetic apeltule, oveLcomes these ploblerns.
In 1952, C. Wiley of the Gooclyeal Airclaft Co. developed an irnaging
raclal witlr fi'equency of 75 MHz, initially ca,lled Doppler beam-sharpeni,tt g
sysfem, whose idea cal l¡e traced back to the papel by Shelwin et al. 1981.
An ilclepentlent experiment with a Dopplel plocessing ladal rvas concluctecl
by the University of lllinois gtoup in 1953 using an airl¡orne coherent X-
barrd pulsecl radar (Brown et al. 113]). The resealch being clevelopecl at the
Univelsity of Illinois rvas transfer::ecl to the Univelsity of Micliigan about 1956
(Ulaby ei ø1. [103]. The classifiecl clevelopment of SAR systems took place
at tlie Ulivelsity of Michigan ancl also at a numbel of cornpanies during the
late 1950's and eally 1960's. The fir'st unclassified papel clesclibing a SAR
systern can be founcl in Curtona et al, 122]1.
The first operational SAR was the Goodyear AN/APQ-102 system. It
rvas an X-barcl (3 crn) horizontally polarized systern built fol militaly use
(Nfoore [80]). hr i969, the synthetic aperture GEMS (Goodyear Electronic
Mapping Systern) l¡ecame available comrnelcially (Moole [80]).
The fir'st extensive geological mapping using ailborle SAR rvas conducted
in easteln Panarna by the United States Auny Engineering Topography Lab
in 1967 (MacDonald [68]). There liad been nirimal success in obtaining
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