Long-Term Gain Stability Evaluation for Microwave Instruments Using Lunar Radiation

Accurate global observations from space are a critical part of the needed knowledge base for global climate change study. However, atmospheric temperature trends derived from space-borne microwave instruments remains a subject of debate, mainly due to uncertainty arise from calibration error and long-term drift and degradation of instrument. 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. In this study, microwave brightness temperature simulation model for moon’s disk was developed and validated based on ATMS space view observations. This model was then applied to evaluate the 5 years NPP ATMS observations since its launch. Results show that ATMS calibration accuracy and stability can be well assessed by taking moon as PRT.