Developing Vicarious Calibration for Smallsat Microwave Instruments using Lunar Radiation

A key issue for microwave cubesats and small satellite constellation is a consistency calibration algorithm. Permanent Reference Target (PRT) with high stability and well-known microwave brightness temperature can not only help to evaluate the instrument calibration accuracy, it can also being used to evaluate the long-term calibration stability of microwave sensors. Radiation of the Moon is very stable in microwave spectrum, attribute to its stable geophysical property. The only factors that change the magnitude of lunar microwave radiation in satellite observations are its surface temperature, which is determined by its phase angle, and its position in the Field of View (FOV). Therefore, there is potential to take the Moon as PRT to evaluate the calibration accuracy and assess the long-term calibration stability for microwave radiometers. In this study, microwave brightness temperature simulation model for moon’s disk was developed and validated based on ATMS space view observations. To demonstrate the effectiveness of proposed lunar calibration model, 5 years lunar observations from NPP ATMS were collected and evaluated by the model simulations. Results show that ATMS calibration accuracy and stability can be well assessed by taking moon as reference calibration target