SWIMSAT: A real-aperture radar to measure directional spectra of ocean waves from space - Main characteristics and performance simulation

The project SWIMSAT aims to measure the directional spectra of waves from space using a real-aperture radar with a low-incidence, conical-scanning beam. This system's design is based on airborne versions developed in France and the United States. In this paper, the authors present the satellite measurement principle and instruments. For this study, the authors developed a simulation method to analyze the sensitivity of wave spectra, taking into account radar observation conditions (spatial resolution, signal-to-noise ratio, integration time, etc.) and inversion processing parameters (noise level and range displacements during temporal integration). The simulation method and results are presented in this paper. The study enabled validation and refinement of the satellite concept. The simulations show that in the chosen configuration, SWIMSAT is capable of measuring wave spectral properties in wind-sea conditions (at dominant wavelengths over approximately 70 m) and swell conditions (at significant wave heights over approximately 1.5-2 m, depending on wind). Unlike for synthetic aperture radar observations, the performance of SWIMSAT in terms of minimum detectable wavelength is independent on the wave propagation direction.