A new approach to retracking ocean and coastal zone multi-mission altimetry
Jennifer Freeman(1) and Philippa A.M. Berry(1)
De Montfort University,
Leicester LE1 9BH,
The primary function of satellite radar altimeters has historically been the measurement and monitoring of the ocean surface. Most researchers utilise pre-processed altimeter products., optimised for precise range measurements to an ocean surface, using retracking algorithms which assume a Brown model waveform. However, a significant number of echoes returned from the ocean surface do not conform to this model. As the coast is approached, the percentage of Brown model echoes decreases rapidly, and the standard processing algorithms reject most of the data.
This paper presents results obtained by reprocessing ocean echoes using a rule-based expert system, which includes both Brown model algorithms and a range of algorithms configured to identify and retrack to ocean components within complex returns. This system also permits a much greater proportion of echoes from sea-ice to be successfully retracked.
Using this system, ocean echoes from the Topex, Jason-1, ERS-1, ERS-2 and Envisat missions have been reprocessed globally, including the ERS-1 Geodetic Mission. Utilising this huge multi-mission dataset, a global comparison is made with results from standard altimeter products, and the enhancements in data quantity and quality which can be achieved using this approach is quantified.