As an expert in altimetry, CLS is involved in the Radar-Altimeter (RA-2) calibration onboard ENVISAT, which was launched in March 2002.
CLS is in charge of two different types of calibration:
Absolute calibration: determination of the absolute bias of RA-2 by comparing tide gauge measurements with altimetry measurements.
Relative calibration: long term monitoring of the RA-2 drift.
CLS tasks:
Absolute calibration of RA-2 in the western part of the Mediterranean Sea
- To compare altimeter data with tide gauge measurements which are not under altimetry tracks, a specific method of comparison was developed.
In situ measurements were propagated towards the satellite tracks by the use of specific algorithms and through geophysical models. The two types of data were corrected from mean sea surface, tides and atmospheric effects.
- Each tide gauge used in the study was absolutely referenced to the geoid. Then, CLS computed an absolute bias for several periods of time of the ENVISAT mission.
Relative calibration of RA-2 over the global ocean
- To monitor the potential drift of RA-2, the altimeter data will be compared to a global tide gauge data set. A relative bias will be computed throughout the ENVISAT mission.
Institutions:
Activities are carried out for ESA.
Users:
Results on data quality are sent to ESA which delivers the data to the users.
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