SOME CONSIDERATIONS ON THE CRYOGENIC CALIBRATION TECHNIQUE FORMICROWAVE AND MILLIMETER WAVE GROUND-BASED RADIOMETRY

Abstract

This manuscript describes the cryogenic calibration technique applied to the MP3000A radiometer, which
employs a liquid nitrogen (LN2) cooled target as a temperature primary calibration standard (black body). This
instrument has recently been deployed in different parts of Brazil as part of the CHUVA Project field campaigns.
Taking into account that a reliable calibration is critical for data retrieval and analysis, a system calibration was
performed at 22 - 30 GHz (K band) and 51 - 59 GHz (V band) frequency ranges emphasizing the systematic evaluation
of the technique. In order to obtain good results for a number of atmospheric parameters, the brightness temperature
observation errors raised by the radiometer should be below 0.5 K. The results show that the errors and deviations in
the brightness temperatures measurements associated to the LN2 calibration are considered satisfactory. However,
further studies must be carried out in order to better understand all the effects involved in the retrieval of atmospheric
parameters and also to outline system precision enhancements.