Airborne optical system for remote sensing of ocean waves

A compact, turret-based optical system has been designed and constructed for passive imaging of ocean waves using a small aircraft. The purpose of the system is to collect time series of images, which are mapped to a common geodetic surface in order to extract the space-time characteristics of the waves. This is achieved by staring at a fixed geodetic location and by accurately measuring the imaging geometry. The system was designed to be compact and lightweight for future installation on an unmanned aerial vehicle and has been installed on a small, manned, single-engine aircraft for testing and experimentation. Initial tests have confirmed successful operation of the staring capability at moderate distances to a fixed target array on land and to the nearshore region with shoaling gravity waves. Images were mapped to a common reference frame on a geodetic surface at the mean ocean level, and a three-dimensional spectrum of the space-time data cube of the mapped image modulations exhibits the expected, well-resolved dispersion surface for surface gravity waves. This paper describes the data collection system, the processing procedures, and the preliminary results.