Sea state monitoring by radar altimeter from a microsatellite.

This thesis constitutes a general survey and a study of significant extensions to the usual conventional satellite radar altimetry. Historically radar altimeter has been configured to the measurement of mean sea level. It is well known that other statistics such as Significant Wave Height (SWH) and wind speed are in principle recoverable from the radar echo and these are currently of great interest. It has been the aim in this thesis to optimize such measurements, for a general meteorological application, with less interest shown in absolute measurement of sea level. Current technology makes possible a total Earth survey using a constellation of small satellites, covering the entire Earth sea surface with short revisit time. Such solutions necessitate less cost, lower power, and less precise attitude control than the scientific satellites used hitherto. The purpose of this thesis is to present a novel two mode radar altimeter for sea state monitoring. SWH is still measured by conventional high-resolution mode, which is not sensitive to off-nadir pointing. An additional novel low-resolution mode is proposed for wind speed measurement. By using this mode, wind speed measurement is much more robust to pointing error than by using conventional high-resolution mode. An improved wind speed measurement can be achieved by using a cost effective small satellite. Some considerable time was also spent on incorporating SAR (Synthetic Aperture Radar) into altimetry techniques to improve the signal to noise ratio. For sea state monitoring the improvements are relatively disappointing, although greater improvement are expected for ice sheet monitoring