Work

Preliminary Study on the Radiating Brightness Temperature Bias for the Microwave Calibration Target Based on Inner-Kernel PRT Measurement

Year: 2026

Type: article

Abstract: The array-shaped microwave calibration target (MCT) is widely applied in the radiometer payloads, with the advantages of compact size and Lambertian thermal radiation. However, it has been noticed that the vertical temperature gradient at unit tips introduces notable brightness temperature (BT) bias, obstructing the achievement to high-accuracy calibration. Meanwhile, the direct testing on the temperature of the coating layer remains as a difficult task, especially when the MCT is mounted on the space-borne payloads, so the BT of the MCT is hard to be accurately determined. In this work, the authors explore the possibility to estimate the BT based on the widely applied platinum resistance thermometer (PRT) in the unit kernel. It is shown in the thermal measurement of a uniform background that the PRT tested temperature at different heights of metal kernel can be distinguishable, and the temperature difference variation agrees with the trend of target-ambient temperature difference. While the PRT has been widely applied to test the aperture temperature homogeneity of the array-shaped MCT, the results in this work indicate that the PRT has the potential to practically detect the vertical temperature gradient in units, which is directly related to the BT bias. Furthermore, the possible manners and main obstruction factors in projecting the PRT tested temperature difference to the BT bias estimation are discussed in this work.

Source: IEEE Geoscience and Remote Sensing Letters

DOI: 10.1109/lgrs.2026.3729968