Preliminary refractivity from clutter (RFC) evaporation duct inversion results from CASPER west experiment

This paper describes how a low cost; marine surveillance radar can be modified for remote sensing of the non-standard lower atmospheric EM propagation conditions. The radar uses the Refractivity-from-Clutter (RFC) technique to estimate atmospheric refractivity profile from sea clutter measurements. For this purpose, a commercial Koden MDS-63R marine radar architecture is converted to a software-defined radar with a vertically polarized 48 dB gain 10 ft. diameter prime focus satellite dish. High speed sampling of the IF data allows all processing to be performed in software. The radar has a 25 kW peak transmit power, uses a long pulse with large range bins, increased clutter power at each bin, and smoother clutter fluctuations due to its design, allowing for better RFC inversions. The radar was deployed in Southern California at Pt. Mugu from September-October 2017 as part of the Coupled Air-Sea Processes and EM Ducting Research (CASPER) West Campaign. Initial results provided demonstrate the radar capability of performing RFC to obtain environmental conditions. The RFC algorithm works by obtaining the environment in which the simulated clutter pattern matches the measured radar data. The environments are simulated by a parabolic wave equation (PWE) algorithm.