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ON-BOARD SAR PROCESSING 
R.W. Okkes 
European Space Research & Technology Centre 
Noordwijk, The Nether!ands 
G. Gaillat 
Matra 
Velizy, France 
R. Schotter 
Dornier Systems GmbH 
Friedrichshafen, Germany 
Comission II 
ABSTRACT 
This paper describes candidate concepts for on-board SAR processing 
covering the associated aspects of applicable algorithms, processing 
system architectures and technology. 
Emphasis is placed on SAR image generation being the most demanding SAR 
pre-processing task. 
i. INTRODUCTION 
The processing of SAR data on-board of the spacecraft may serve two 
objectives: 
a) enhancement of mission capabilities, and 
b) improvement of facilities for data usage. 
Enhancement of mission ~apabilities is achieved because on-board SAR 
imagery generation and coding provides for data volume reduction as 
compared to the amount of raw data generated by the sensor, which 
alleviates data transmission, data handling and on-board recording 
constraints. 
The utilisation of sensor data may be improved because of the inherent 
capability of on-board processors to provide desired data products in real 
time being delivered to local relatively simple ground receiving stations 
for further processing or direct usage. 
The type of processing envisaged can be characterised by its typical 
end-product i.e.: 
a) SAR image generation 
b) SAR image encoding 
c) Data extraction (user oriented processing) 
The image generation step can be considered as a necessary one for all 
follow-on processing and is therefore commonly identified as a 
"pre-processing" step. 
The main processing parameters are related to the multi-look detection 
operation, providing a trade-off between image spatial resolution and the 
amount of "speckle", the latter disturbing component being introduced by 
the coherent microwave signal sensing mechanism. Apart from the selection 
of the multi-look operation the image generation step is essentially not 
effected by the user, which may consider its output as being generated by 
a microwave imaging sensor with predefined system characteristics.