542 
JPL SAR PROCESSOR DEVELOPMENT IN 
SUPPORT OF FLIGHT MISSIONS 
Chialin Wu 
Jet Propulsion Laboratory 
California Institute of Technology 
Pasadena, CA 91109, USA 
Commission II, ISPRS 
Abstract 
This paper presents an overview of Synthetic Aperture Radar (SAR) signal 
processor development activities at the Jet Propulsion Laboratory (JPL) in 
support of NASA sponsored airborne and spaceborne SAR flight missions. The 
processors being developed include both computer software oriented and 
special-purpose hardware systems. The contents of the paper include a 
summary of the anticipated missions, functional specifications and descriptions 
of the associated processors, and a few related issues. 
1I. ‘Introduction 
Synthetic Aperture Radar (SAR) signal processing for image formation is one 
of the key steps in operating an end-to-end SAR sensor and data system. 
Unlike an optical imaging device where the sensor acquired raw data may 
already be in image form, micro-wave imaging sensor like a SAR acquires raw 
data in a form resembling a holographic representation of the target scene. 
The raw data must go through an extensive amount of processing to forma 
product that is in a conventional and interpretable image format. 
The arithmetic processsing to reduce SAR raw data into imagery can further 
be complicated by a number of factors that are peculiar in each SAR flight 
mission. These factors include the choice of radar frequencies, tolerance 
of sensor attitude and altitude uncertainties, experiment objectives, etc. 
The processor implementation on one hand must be an integrated part of the 
sensor system design such that the method to accommodate mission peculiarities 
would be handled from an overall system optimization point of view. It is 
equally important on the other hand that the processor's performance is 
compatible to real users' needs in terms of data quality and output speed. 
JPL's on-going SAR processor development activities can be categorized into 
those that are supporting current missions, and those for future anticipated 
missions. Current missions include the CV-990 Aircraft flights and Shuttle 
Imaging Radar-B (SIR-B) Experiment. Functional requirements for the associated 
SAR processors are well defined. For some of the future missions, which 
include Venus Radar Mapper, SIR-C Experiment, etc., some assumptions on data 
parameters have to be made. One important objective for the research and 
development on the SAR processor is to also demonstrate the feasibility of 
SAR signal processing at a very high rate -- near real-time data acquisition 
speed. This processing throughput rate is required for the ultimate goal of 
real-time SAR applications in environment monitoring. It also serves a near 
term significance of further ensuring that users needs for image products 
can be met in a timely manner. A programmatic overview of those ongoing SAR 
processor development activities will be given in the next part of this 
paper.