RA-2/MWR in-flight performance - preliminary results

The EnviSat-1 satellite embarks an innovative radar altimeter, the RA-2, which represents a new generation of radar altimeters compared the earlier ERS altimeters and TOPEX/Poseidon. This is due to its use of many advanced features such as autonomous resolution selection a robust "model free" tracker and its ability to telemeter individual echo samples. EnviSat also embarks a radiometer, the MWR which provides the altimeter with the tropospheric correction. Before the measurements from the RA-2 are exploited the instrument and the data processing system will be commissioned and a verification activity will be performed. During this activity the operation of the instrument in-flight operation will be verified and its functionality optimised. The measurement performance of the instrument and the overall system will also be evaluated, including verification of the instrument auxiliary data retrieval and correct use of these data in the ground processing algorithms. Finally, calibration and validation of the data products are performed such that, at the end of the commissioning phase, the data may be fully released for scientific exploitation. In this paper we will outline the strategy and procedures adopted to tune the parameters used on-board and in the on-ground processing. We show results before and after the optimisation activities as well as comparison with pre-flight simulations. Also, we will show the RA-2 measurement performance of range and sigma-0 as well as the performance of its tracker. In particular the tuning of the autonomous range resolution selection logic is a challenging task and we will show the results of this activity. Finally we will show the status of the in-flight calibration of the Range and Sigma-0.