Envisat ocean altimetry performance assessment: continuity and improvement of the ERS series
Yannice Faugere(1) , Joël Dorandeu(1) , Nicolas Picot(2) , and Pierre Femenias(3)
8-10 rue Hermes, Parc Technologique du Canal,
(2) CNES, 18, Av. Edouard BELIN, 31401 Toulouse Cedex 9, France
(3) ESA, Via Galileo Galilei CP64, I-00044 Frascati, Italy
With more than three years of altimetric measurements over ocean Envisat not only ensures the continuity of the observations provided by ERS-1 and ERS-2, but significantly improves the data quality. The quality assessment of these data is routinely performed at the CLS Space Oceanography Division in the frame of the CNES Segment Sol Altimétrie et Orbitographie (SSALTO) and ESA French Processing and Archiving Center (F-PAC) activities. This poster presents the main results in terms of Envisat data quality and performances: verification of data availability and validity, monitoring of the most relevant altimeter (ocean1 retracking) and radiometer parameters, assessment of the Envisat altimeter system performances.
Envisat carries a new generation of dual frequency radar altimeter (RA-2) which allows correction of ionosphere effects and a Microwave Radiometer (MWR) for wet troposphere path delay retrieval. From statistical and spectral analysis, it appears that a low amount of ocean data is discarded by conventional editing procedures compared to other missions and that a low level of noise is found on 1Hz data. In addition, the presence of a Doris receiver allows high precision orbit determination, highly improved compared to ERS.
Thus the Envisat altimeter mission reaches the high level of accuracy of other precise missions such as T/P and Jason-1. From cross-calibration analysis, also included in this work, the Envisat precise altimeter measurements can be merged with data from other missions in a multi-mission altimeter dataset.