EVOLUTION OF DIGITAL GROUND SAR PROCESSING SYSTEMS 
J.' Gredel,.H. Schröter 
DFVLR, Deutsche Forschungs- und Versuchsanstalt 
für Luft- und Raumfahrt 
Federal Republic of Germany 
Commision II 
ABSTRACT 
án increasing number of airborne and spaceborne Synthetic Aperture Radar 
(SAR) systems are used for a variety of remote sensing applications and more 
than 30 digital SAR processors have been developed worldwide since the launch 
of SEASAT. 
Presently there are four types of digital SAR processors, existing or under 
development. Typical implementation concepts are: 
* software on a general purpose computer, primarily used for algorithm 
development and experimental purposes 
. software on a minicomputer augmented by array processor(s), used for 
experimental purposes as well as for operational tasks with low through- 
put requirements 
. multiprocessor systems designed for high throughput operational process- 
ing 
. hardware configurations for Real Time and Near Real Time processing 
This paper presents the evolution of the different SAR processors in a retro- 
Spective view and describes the actual status of all known ongoing develop- 
ments based on a survey, that was updated periodically over the last three 
years. 
A cautious extrapolation of future processor development concludes the 
paper. 
1. INTRODUCTION 
The development of digital SAR processing technology for civil application 
has been triggered primarily by the first spaceborne L-band SAR carried on 
the SEASAT satellite. Although appropriate digital processing systems were 
not available during the lifetime of the satellite fAug./Oct. 1978), shortly 
after several systems became operational and a variety of additional exper- 
imental systems have been developed meanwhile. 
À first survey of SAR processors was presented by Guignard (1981) and updated 
later by Raney (1982) and Gredel (1982/83). The present paper finally con- 
cludes the series of updates with latest available information. It has to be 
seen in context with more detailed information prepared for this conference 
(Working Group II-5). More than 30 different processing systems from 16 
organisations in North America, Europe and Japan are briefly characterized in 
terms of hardware configuration, algorithm, throughput and application. 
Future plans are mentioned and references are given. 
The relevant information has been compiled from questionnaires that were 
returned from organisations known to develop or operate SAR processing sys- 
tems.