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The Microwave Humidity Sounder (MHS): in-orbit performance assessment

The Microwave Humidity Sounder (MHS) is the high-frequency microwave radiometer of the ATOVS (Advanced TIROS Operational Vertical Sounder) instrument suite of the IJPS (Initial Joint Polar System), the current joint EUMETSAT-NOAA programme for operational satellite meteorology. Five MHS models have been built by Astrium Ltd under EUMETSAT contract, two of which are currently operational on the NOAA-18 and Metop-A satellites. The MHS instrument replaces the former AMSU-B in the operational microwave sounder suite. This paper provides a summary description of the MHS instrument and describes in some detail its in-orbit performance and functionality, along with a comparison with similar instruments. The in-orbit performance has been extensively assessed during the SIOV (Satellite In-Orbit Verification), the first part of the commissioning phase aimed at activating the payload and verifying its operation, and is periodically monitored throughout the mission life. The performance relevant to the SIOV and operational phase of the MHS instruments on both NOAA-18 and Metop-A are presented. With respect to its predecessor AMSU-B, the MHS instrument constitutes a sensible improvement in terms of radiometric sensitivity and calibration accuracy, while allowing full continuity of the acquired data and relevant processing.