Ocean Surveillance Statistical Considerations
Abstract
Several statistical topics were studied concerning detection of targets on the ocean's surface from a satellite-based radar. First, a desired signal-to-noise ratio was obtained by considering the tradeoff between false alarms and detected targets. For a 0.99 detection probability and 10 to the - 10th power false alarm probability the S/N ratio would be 16 db for a nonfluctuating target. Second, the decorrelation times of sea clutter were calculated and found to be so small that for side-looking radars sea clutter samples are independent from pulse to pulse but found to be so large for forward-scanning radars that one finally obtains decorrelation from sea motion instead of from platform motion. Third, a fluctuating target was considered, and the losses were calculated and compared with those of a nonfluctuating target. Roughly, one needs 1 to 4 db more power to detect a fluctuating target as opposed to a nonfluctuating target. Then, the ionosphere was considered, and the effects of Faraday rotation and the random phase shift were calculated. Degradation varies from intolerable below 900 MHz to negligible at 3 GHz. Next, some of the aspects of data processing were studied; the optimal integration angle was found, the optimal weighting was calculated, and azimuthal position estimators were considered. Surprisingly, optimal weighting gives a pattern only 0.3 db better than uniform weighting. Finally, a way was determined of using an adaptive threshold and soft limiting to maintain a constant false alarm rate.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 27, 1968
- Accession Number
- AD0394650
Entities
People
- Gerard V. Trunk
Organizations
- United States Naval Research Laboratory