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In 2002, two spaceborne microwave radiometers were launched to provide new observation data. One sensor is the Advanced Microwave Scanning Radiometer (AMSR), aboard the Advanced Earth Observing Satellite-II (ADEOS-II) of the National Space Development Agency of Japan (NASDA). The other is AMSR-E, aboard Aqua of the National Aeronautics and Space Administration (NASA). AMSR and AMSR-E are almost identical sensors, and have lower frequencies 6 and 10 GHz, in comparison with preceding sensors, such as the Special Sensor Microwave/Imager (SSM/I). In addition to geophysical products currently retrieved from the SSM/I, new products of sea surface temperature and soil moisture have been retrieved from AMSR and AMSR-E by using those lower frequencies. Eleven Principal Investigators were assigned by NASDA to develop algorithms to retrieve geophysical products, and their programs have been installed at the Earth Observation Research Center of NASDA. Geophysical products are currently being validated by several methods, such as using existing in situ data, employing instruments in field observations, and comparing data with other sensor's data.
Shibata et al. (Sat,) studied this question.