The Microwave Humidity Sounder (MHS) is an instrument launched on NOAA's POES

Polar Operational Environmental Satellites

The Polar Operational Environmental Satellite project operates a constellation of weather satellites in polar orbits around the Earth. It is a joint effort between the National Oceanic and Atmospheric Administration and the European Organisation for the Exploitation of Meteorological Satellites...

 satellite series starting with NOAA-18

NOAA-18

NOAA-18 is a weather forecasting satellite run by NOAA. NOAA-N was launched on May 20, 2005, into a sun-synchronous orbit at an altitude of 854 km above the Earth, with an orbital period of 102 minutes. It hosts the AMSU-A, MHS, AVHRR and High Resolution Infrared Radiation Sounder instruments, as...

 launched in May 2005 and European Space Agency

European Space Agency

The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

's MetOp

MetOp

MetOp is a series of polar orbiting meteorological satellites operated by the European Organisation for the Exploitation of Meteorological Satellites. The satellites are all part af the EUMETSAT Polar System. It is intended to replace the soon to be retired TIROS network...

 series starting with MetOp-A launched in October 2006. It is a five-channel passive microwave radiometer, with channels from 89 to 190 GHz. It is very similar in design to the AMSU-B

Advanced Microwave Sounding Unit

The Advanced microwave sounding unit is a multi-channel microwave radiometer installed on meteorological satellites. The instrument examines several bands of microwave radiation from the atmosphere to perform atmospheric sounding of temperature and moisture levels.-Products:Level-1 radiance data...

 instrument, but some channel frequencies have been altered. It is used to study profiles of atmospheric water vapor

Water vapor

Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...

 and provide improved input data to the cloud-clearing algorithms in IR/MW sounder suites.

The Microwave Humidity Sounder has been designed and developed by Astrium EU in Portsmouth UK, under contract to EUMETSAT.

Instrument Characteristics

• Heritage: AMSU-B, HSB
  Humidity Sounder for Brazil
  The Humidity Sounder for Brazil was an instrument launched on NASA's Earth Observing System satellite Aqua launched in May 2002. It was a four-channel passive microwave radiometer, with one channel at 150 GHz and three channels at 183 GHz. It was very similar in design to the AMSU-B instrument,...
  
  
• Swath: 1650 km
• Spatial resolution: 17 km horizontal at nadir
  Nadir
  The nadir is the direction pointing directly below a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface there. Since the concept of being below is itself somewhat vague, scientists define the nadir in more rigorous...
  
  
• Mass: 63 kg
• Duty cycle: 100%
• Power: 74 W (BOL)
• Data rate: 4.2 kbit/s
• Field of View: ± 49.5 degrees cross-track
• Instrument Instantaneous Field of View: 1.1 degrees circular

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	89.9 ± 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