Improving the measurements of high frequency radar: Reduced averaging times and bistatics

Abstract

High Frequency radar has been operational with the US Coast Guard since May 2009. The long-range SeaSonde is a key component of the national HF radar network. Default SeaSonde processing on long-range systems only captures 92% of the M2 tidal current velocity and hence 85% of the tidal energy due to a 180-minute averaging time. Reducing this averaging time would help improve the surface current measurements of the SeaSonde system. A study was undertaken to analyze the radial processing of the long-range SeaSonde. Radial current files were generated using a sixty-minute radial averaging and compared with the default one hundred and eighty minute average. This was performed at five stations in the northern section of the Mid Atlantic Regional Association Coastal Ocean Observing System (MARACOOS) for a two-week period. This study has implications for the thirty-five long-range radars operating in the United States and the approximately eighty-six long-range radars operating around the globe. The hope being that the shorter averaging time will lead to increased accuracy of the measured surface currents. This in turn will lead to more effective search and rescue cases for the US Coast Guard. Another study was conducted to measure the impact that bistatic radar has on the measurements of surface currents. A 13 MHz radar network was used to test to see if elliptical current measurements would decrease the uncertainty of a total surface current measurement. A three-week record of hourly radial and elliptical measurements were used and combined in several configurations to test the impact of the elliptical currents. Initial findings show that the elliptical current measurements decreased the uncertainty of the total vector calculation and reduced gaps due to missing radial data.