Measurement of wave slope asymmetry from a Multistatic Space Lidar Constellation: Theory and preliminary analysis of Wind direction Retrievals
Résumé
Recently, the National Ocean Partnership Program funded the phase A of a lidar cubesat mission: Rainbow. This mission aims to provide information about surface height, surface vector winds, sea-ice, coastal land surface and liquid water clouds. Depending on the final system characteristics, it could also contribute to our knowledge of coastal ocean turbidity and ecology. We propose here to focus on the wind vector retrieval. Wind is a major source of momentum to the upper ocean and modulates the coupling between the atmosphere and the ocean. In littoral areas, wind influences economic activities like ship navigation and fisheries. The Lidar can provide a retrieval of wind properties closer to the coastlines and at a finer scale than typical microwave systems. We will present the theoretical basis of how the lidar can retrieve the wind speed through the surface roughness measurement [1] and wind direction from the multistatic measurement of the wave slope asymmetry. It is well known that the upwind and crosswind components of the mean square slope are drastically different [2] and several lidar receivers looking at the laser light coming from different directions will be sensitive to this asymmetry. The CALIPSO lidar mission has conducted several large off-nadir angle maneuvers (10° to 30° off-nadir) that show this signature of wind direction but with a limited ability for retrieval because it's a single monostatic system. We will present a preliminary analysis of these data and an overview of the features of the Rainbow mission that will allow us to retrieve wind vector from a cubesat lidar constellation.