HF Radar Calibration with Automatic Identification System Ships of Opportunity

Of more than 100 HF Radars operating within the Integrated Ocean Observing System (IOOS), more than half run either without recommended receive antenna pattern calibrations or with out-of-date calibrations, despite potential compromises to data quality.Cost is the primary inhibitor of frequent calibration, which generally requires a technician to drive a small vessel with mounted transponder in arcs around the antenna.Large vessels now broadcast their positions and speed approximately every 10 seconds using the Automatic Identification System (AIS).Echo from these vessels also appear as signals in real-time HF Doppler spectra.We propose using AIS ship position and speed, along with corresponding HF Doppler ship echo, to determine receive antenna patterns in near real time.The methods proposed here will result I a software product which would both reduce the cost of calibration of IOOS HF radars and significantly improve IOOS surface current data quality.