Bandwidth Compression Of Synthetic Aperture Radar Imagery By Quantization Of Raw Radar Data

Aircraft and spacecraft employing Synthetic Aperture Radar (SAR) as a sensor will either have to perform on-board processing before telemetry or directly transmit the raw radar returns back to a ground station for processing. Although complete or partial on-board processing deservedlyis receiving careful attention, present technology seems to favor ground station processing requiring extremely high data rates to telemeter the raw radar returns. The usual bandwidth compression strategies utilizing redundancies in the scene being transmitted are inapplicable, however, since the radar returns from even adjacent resolution cells are approximately uncorrelated. Therefore, we turned to quantization of the radar returns to achieve some data rate reduction. In this study, we have investigated the effects of quantization by observing output images after one-bit, two-bit, and eight-bit quantization of the raw radar data. By comparison with the original image (ground truth), we can determine the degradation resulting from data or bandwidth reduction by quantization. Furthermore, the telemetry data rate can also affect output picture quality since transmission errors may be functions of the data rates. To investigate this circumstance, we introduced bit errors with probabilities of 2-4 and 2-7. The former being much higher than that expected in "normal" operation, presents a worse case situation, while the latter may be fairly indicative of telemetry links of early space missions using SAR's. We present output images that have been contaminated at these bit error rates.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.