Design and Characterization of a Peltier-Cold Calibration Target for a 110-GHz Radiometer

Blackbody targets are needed for the calibration of radiometers for remote sensing applications. The use of hot and cold references is essential for an accurate calibration. Commonly, the cold loads are made with liquid nitrogen, but for a campaign instrument, this is not a sustainable option. In this paper, we present the design, construction, and characterization of a new cold calibration target for a microwave radiometer operated at 110 GHz for the detection of pressure-broadened spectra from atmospheric ozone. The target is cooled with Peltier elements. Heat transfer simulations were made to optimize the design and minimize temperature gradients. Several tests were performed with a vector network analyzer, a radiometer, and a network of thermometers in order to characterize the blackbody built. Results show a homogeneous temperature along the absorber surface, notably low reflections, and a very high emissivity.