The EnviSat RA-2/MWR instrument description, processing chain and data products

Within the ESA Ground Segment, all the Radar Altimeter (RA-2) and Microwave Radiometer (MWR) received data will be systematically processed to Level 1B (geolocated and calibrated engineering parameters) and to Level 2 (geophysical data record). All data will be processed in near real time (availability to users within three hours from data take), then reprocessed as Intermediate GDR (within 3 days) and later in off-line (few weeks after data take). The three version of the Level 2 product have the same layout and provide the typical information of the classical GDR altimeter product. The main difference among them is constituted by the increasing quality of the used orbit. Another main feature of the Level 2 RA-2 product is that every received waveform is processed in parallel by four different algorithms (each one optimised for a particular type of surface: ocean, sea ice, ice 1, ice 2). The Level 2 product (in all its versions) contains the results of the four retracking processes. The Level 1b product NRT and Off-line and the Level 2 NRT products are generated in the ESA station, while the IGDR and the Off-line GDR are produced for ESA by the French Processing and Archiving Centre. Concerning the geophysical corrections, it is important to note that the corresponding MWR measurements are used to correct for the wet tropospheric component, while the dry tropospheric component is corrected making use of the pressure field predicted or reconstructed by ECMWF (European Centre for Medium-Range Weather Forecast)