Microwave Imager/Sounder (MIS)
The National Polar-orbiting Operational Environmental Satellite System (NPOESS) is developing the Microwave Imager/Sounder (MIS) as replacement for the Conical-scanning Microwave Imager/Sounder (CMIS).The NPOESS MIS will continue the legacy measurements of the DMSP Special Sensor Microwave Imager/Sounder (SSMIS) and the Special Sensor Microwave Imager (SSM/I) that are critical to operational weather forecasting, climate monitoring and earth science. The first MIS sensor is scheduled to fly aboard the second NPOESS spacecraft (C2), which is expected to launch in 2016. The MIS will perform key measurements for NPOESS including Soil Moisture and Sea Surface Winds. Other environmental parameters related to conical-scanning microwave radiometers and MIS include Atmospheric Temperature and Moisture Profiles, Sea Surface Temperature, integrated atmospheric moisture and precipitation measurements.
The NPOESS IPO competitively selected the Naval Research Laboratory (NRL) in 2008 to design and build the MIS because of its demonstrated experience and knowledge developing the first space-borne polarimetric microwave radiometer, WindSat, operating successfully since 2003. As part of the MIS design work there is a need to process analysis data and compute the performance of the antenna system to enable comparison with sensor specification requirements. To achieve this goal, CPI was tasked by NRL to adapt the WindSat Ground Data Processing System (GDPS) software for use with MIS. CPI was selected because of its highly rated implementation of the WindSat GDPS. This was a natural transition for CPI because of its prior involvement in developing the WindSat GDPS, and the MIS sensor sharing many channel configurations similar to the WindSat instrument. The retrieval algorithms developed as part of the WindSat GDPS are being adapted to retrieve the same physical quantities from the MIS data, thereby enabling a rapid and smooth implementation of the MIS GDPS.
In tandem with the GDPS development, CPI is involved with NRL personnel in MIS land algorithm development, Faraday rotation correction, and antenna design. A physically-based land algorithm is currently being developed to simultaneously retrieve the soil moisture, land surface temperature and vegetation water content for a range of surface types. The algorithm has been rigorously validated against global in-situ data and has demonstrated great science potential in the study of soil moisture response to precipitation, ITCZ (Intertropical Convergence Zone) propagation, drought detection, and heat wave evolution. Work is also in progress to estimate the correction due to Faraday rotation to improve the wind retrieval accuracy in the data provided by WindSat and MIS. Faraday rotation occurs due to the linearly polarized field components in the microwave radiation becoming rotated through an angle as a consequence of charged particles and the Earth's magnetic field. Correcting for this rotation is important for improving the accuracy of wind vector retrievals in the Windsat and MIS programs. As part of the MIS project, analysis tools are also being developed to process analysis data and compute the performance of the antenna system to enable comparison with sensor specification requirements. This includes computing high-level parameters in the antenna specifications, and showing visual representations of antenna performance to make it understandable.
The MIS sensor concept showing key aspects of the electrical and mechanical sensor subsystems (Graphic courtesy of Naval Research Laboratory).
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