Antenna calibration for oceanographic radars using aerial drones

We describe using small drone aircraft for antenna pattern measurements (APMs) of high-frequency (HF) oceanographic radars for observing ocean surface currents. Prior studies show that accurate surface current measurements using HF radar require APMs. Typically APMs are obtained using small research vessels carrying radio signal sources or transponders in circular arcs around individual radar sites. This procedure is expensive because it requires sea-going technicians, a vessel, and other equipment necessary to support small boat operations. Furthermore adverse sea conditions and obstacles in the water can limit the ability of small vessels to conduct APMs. We have found that drone aircraft can conduct APMs at lower cost and in a broader range of sea states with comparable accuracy. This simplified process for obtaining APMs can lead to more frequent calibrations and improved surface current measurements.