A real-time data acquisition and signal processing system for isro's airborne synthetic aperture radar (asar)

An On-board Real Time Data Acquisition and Signal Processing (DASP) System has been developed for Indian Space Research Organisation's (ISRO) C-band Airborne Synthetic Aperture Radar (ASAR). One of its constituent, the Data Handling and Control Unit (DHCU) assists the operator in centralised initialisation, configuration, control and monitoring of the complete ASAR system during flights and also carries out data acquisition, recording and certain motion compensation related tasks. The other digital unit, the Real Time Processor and Display (RTPD) system, is utilised for continuous monitoring of ASAR performance during imaging sessions and also performs estimation of some parameters critical for ASAR motion compensation. The RTPD system is configured for generating a true multi-look selectable limited swath ASAR image with moderate resolution or a full swath image with a reduced resolution. It carries out, in real time, azimuth signal compression of the range compressed radar returns, tracking of Doppler Centroid frequency and fine estimation of the along track velocity of the aircraft using autofocus technique. The line-by-line scrolling multi-look ASAR image is displayed on a high resolution display monitor, along with certain important annotation parameters in engineering units for image identification. The system also supports an off-line processing mode, wherein quick look ASAR images can be generated by replaying the raw data, recorded on a High Density Digital Tape recorder. The multi-processor hardware architecture of RTPD is based on Motorola's DSP56001 digital signal processors. This paper describes the design requirements, configuration details, processor algorithm, architecture details and salient performance features of this Real Time Data Acquisition and Signal Processing system for ASAR.