High-sensitivity spectral resolution MM-wavelength 18–23 GHz radiometer

High-sensitivity, high-spectral-resolution solar observations in the millimeter wavelength are scanty. A sensitive radiometer with 1 GHz resolution, operating between 18 and 23 GHz in conjunction with a 13.7 m diameter antenna has been in regular operation since the end of 1987. At present, each frequency is sampled for 100 ms, soon to be improved to 50 ms. Details of this instrumentation, including the processes of calibration, data acquisition, and reduction are described here. Also, preliminary observations of an active region and of the burst components are briefly described.