Estimates of Radial Current Error from High Frequency Radar using MUSIC for Bearing Determination

Quality control of surface current measurements from high frequency (HF) radar requires understanding of individual error sources and their contribution to the total error. Radial velocity error due to uncertainty of the bearing determination technique employed by HF radar is observed with both direction finding and phased array techniques. Surface current estimates utilizing Multiple Signal Classification (MUSIC) direction finding algorithm with a compact antenna design are particularly sensitive to the radiation pattern of the receive and transmit antennas. Measuring the antenna pattern is a common and straightforward task that is essential for accurate surface current measurements. Radial current error due to the a distorted antenna pattern is investigated by applying MUSIC to simulated HF radar backscatter for an idealized ocean surface current. A Monte Carlo type treatment of distorted antenna patterns is used to provide statistics of the differences between simulated and estimated surface current. RMS differences between the simulated currents and currents estimated using distorted antenna patterns are 3-12 cm/s greater than those using perfect antenna patterns given a simulated uniform current of 50 cm/s. This type of analysis can be used in conjunction with antenna modeling software to evaluate possible error due to the antenna patterns before installing a HF radar site.