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The Microwave Humidity Sounder (MHS) is one of the European instruments carried on MetOp-A. MHS is a five-channel, total power, microwave radiometer designed to scan through the atmosphere to measure the apparent upwelling microwave radiation from the Earth at specific frequency bands. Since humidity in the atmosphere (ice, cloud cover, rain and snow) attenuate microwave radiation emitted from the surface of the Earth, it is possible, from the observations made by MHS, to derive a detailed picture of atmospheric humidity with the different channels relating to different altitudes. Temperature at the surface of the Earth can also be determined.
MHS works in conjunction with four of the American instruments provided by the National Oceanic and Atmospheric Administration (NOAA), namely the Advanced Microwave Sounding Unit–A1 (AMSU-A1), the Advanced Microwave Sounding Unit–A2 (AMSU-A2), the Advanced Very High Resolution Radiometer (AVHRR) and the High Resolution Infrared Sounder (HIRS). Along with these instruments, MHS is already in operation on the NOAA-18 satellite, which was launched in May 2005, and it will also form part of the payload on NOAA-N' to be launched in 2008. MHS represents a significant enhancement in performance over the AMSU-B currently flying on the earlier NOAA-15,-16 and -17 satellites.
In conjunction with these American instruments, the MHS instrument will provide improved data for weather prediction models with a resulting improvement in weather forecasting..
MHS is intended primarily for the measurement of atmospheric humidity. It will measure cloud liquid water content. Furthermore, it will provide qualitative estimates of precipitation rate.
MHS helps to ensure the continuous and improved availability of operational meteorological observations from polar orbit whilst providing Europe with an enhanced capability for the routine observation of the Earth from space, and in particular, to further increase Europe's capability for long-term climate monitoring.
The Microwave Humidity Sounder (MHS) instrument is a five-channel self-calibrating microwave rotating radiometer on the nadir-facing side of the MetOp-A satellite and is designed to scan perpendicular to the direction flight (across track) at a rate of 2.67 seconds per scan. The swath width of the scan is approximately +/- 50°. The scan is synchronised with the AMSU-A1 and A2 instruments, with MHS performing three scan cycles for every one performed by the AMSU instruments.
The MHS incorporates four receiver chains at 89 GHz, 157 GHz and 190 GHz, with the 183 GHz data sampled in two discrete bands to provide the five channels. The fifth channel is achieved by splitting the 183.311 GHz signal into two channels, each with a different bandwidth.
The scanning of the MHS instrument is synchronized to the scanning of the AMSU-A1 and AMSU-A2 instruments. This allows additional ground processing of data to be performed, using data from selected channels from several of these instruments at the same time. This will provide additional scientific information, which would not otherwise be available from any one instrument alone.
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The NOAA series Platform and MetOp-A Programme
The NOAA-POES series are regarded as the backbone of the US meteorological program. The current POES series satellites are named simply NOAA-9 through NOAA-17 in order of launch. The program has evolved over several years starting in 1960 with TIROS. The philosophy of NOAA is to maintain at least two operational satellites in complementary orbit. The POES satellites will operate till 2010.
All NOAA-POES satellites have a circular, sun-synchronous polar orbit with a nominal flight height of 833 km. The even numbered satellites cross the equator at local solar times of approximately 7:30 and 19:30, while the odd-numbered satellites cross the equator at local solar times of approximately 2:30 and 14:30.
For further details concerning the NOAA satellites look at the NOAA internet sites ( NOAA - documentation ).
The Meteorological Operational satellite programme is a new European undertaking providing weather data services that will be used to monitor climate and improve weather forecasts. The MetOp-A programme’s series of three satellites has been jointly established by ESA and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), forming the space segment of EUMETSAT's Polar System (EPS). MetOp-A has been designed to work in conjunction with the NOAA satellite system whereby the two satellites fly in complementary orbits. MetOp-A’s polar orbit is Sun synchronous, so that the satellite track along the Earth is always at the same local time, in this case in the mid-morning. NOAA will continue to operate its mid-afternoon orbit satellite service as part of the Polar Orbit Enviromental Satellites (POES) system.
The MetOp-A satellites, have been designed to embark instruments provided by NOAA, EUMETSAT, ESA and other European partners. MetOp-A will have different performances than the actual NOAA system due to a platform designed with high pointing accuracy, full on board recording capacity, digital high rate and low rate communication system, encryption capability and an increased payload.
Other Instruments on the Metop-A platform include the Advanced Scatterometer ASCAT, the Global Ozone Monitoring Experiment GOME-2, the Global positioning system Receiver for Atmospheric Sounding GRAS, the High Resolution Infrared Sounder IASI, the Advanced Microwave Temperature Sounder AMSU, the Advanced Very High Resolution Radiometer AVHRR.
MetOp-A’s main objectives are to furnish data for operational meteorology and climate monitoring. Many of the above instruments will give detailed information on the atmospheric temperature/humidity profiles, essential for weather forecasting.
If you would like to have more information about the MHS data, please contact firstname.lastname@example.org.