Ground-based microwave radiometer design and real-time calibration for ocean remote sensing

A multi-frequency, ground-based microwave radiometer (MWR) for ocean remote sensing has been designed and developed in this paper. It will be used on the offshore oil platform and provide atmospheric soundings of physical temperature and liquid water vapor using channels in the oxygen resonance band (6.8GHz) and water vapor resonance band (23.8GHz). The other channels at 10.7GHz, 18.7GHz and 37GHz are used as atmospheric windows, each with dual polarization. The measurements at various combinations of these frequencies and polarization will obtain many geophysical parameters such as the sea-surface temperature, near-surface wind speed, sea ice types and so on. The multi-frequency microwave radiometer is a five frequencies, ten channels and linear polarization system. The receiver is working at total-power mode with super heterodyne style. And the data processing and system control unit is used of operating mode control, data acquisition and digitizing, automatic gain control, state control of the radiometer system and communication with the remote computer system by asynchronous serial interface. Besides, an absolute calibration and a quasi-real-time calibration method used in the multi-frequency MWR are presented and the relative result is also discussed, which guaranteed the high resolution of the multi-frequency microwave radiometer system.