The Radar Altimetry mission: RA-2, MWR, DORIS and LRR

The Altimetry mission on Envisat will extend the time series of observation s started by ERS-1, and the new features of the RA-2 instrument will improv e the quality of the measurements in many respects. The new on-board algori thms for tracking the surface, the larger range window and the extra low-re solution mode will all improve data acquisition over the important ice-shee t margins and over most land and wetland surfaces. New, in-situ ionospheric corrections from the dual radar frequency will be a significant improvemen t on the model-based corrections used on previous missions. The more precis e DORIS orbit will improve the precision of all measurements, particularly in near-real time. The near-real-time products will be built with the same algorithms as the offline final precision products (only some auxiliary inp ut data may differ), thus providing near-high-quality geophysical-data-reco rd products within 3 hours of observation to support near-real-time oceanog raphy.