The Microwave Humidity Sounder (MHS) is a five-channel passive microwave radiometer, with channels from 89 to 190 GHz. It is very similar in design to the AMSU-B instrument, but some channel frequencies have been altered. It is used to study profiles of atmospheric water vapor and provide improved input data to the cloud-clearing algorithms in the IR and MW sounder suites. Instruments were launched on NOAA's POES satellite series starting with NOAA-18 launched in May 2005 and the European Space Agency's MetOp series starting with MetOp-A launched in October 2006, continuing with MetOp-B launched in September 2012 and Metop-C launched in November 2018. The follow on instrument to MHS is MWS on the Metop-SGA satellites.[1]
The Microwave Humidity Sounder was designed and developed by Astrium EU in Portsmouth, UK, under contract to EUMETSAT.
Table 1: Radiometric characteristics of the MHS
| Channel Number | AMSU-B Channel Number | Frequency (GHz) | AMSU-B Frequency (GHz) | Bandwidth (MHz) | Instrument Sensitivity NEDT (K) | Polarization |
| 1 | 16 | 89.0 | 89.0 ± 0.9 | 2800 | 0.22 | Vertical |
| 2 | 17 | 157.0 | 150 ± 0.9 | 2800 | 0.34 | Vertical |
| 3 | 18 | 183.311 ± 1.00 | 183.31 ± 1.00 | 2 x 500 | 0.51 | Horizontal |
| 4 | 19 | 183.311 ± 3.00 | 183.31 ± 3.00 | 2 x 1000 | 0.40 | Horizontal |
| 5 | 20 | 190.311 | 183.31 ± 7.00 | 2200 | 0.46 | Vertical |