In-flight calibration and monitoring of the TROPOMI-SWIR module

Abstract. During its first year in operation the SWIR module of the TROPOMI instrument was calibrated in-flight and its performance was monitored. In this paper we present the results of the in-flight calibration and the ongoing instrument monitoring. This includes the determination of the background signals, noise performance, ISRF stability and stray-light stability. From these results, the number of incurred dead and bad pixels due to cosmic-ray impacts is determined. The light-path transmission is checked by monitoring internal lamp and diffuser stabilities. Due to its high sensitivity for Earth radiation on the eclips side, the calibration strategy for the background (i.e. dark flux and offset) monitoring was adjusted. Trends over the first full year of nominal operations reveal a very stable SWIR module with little to no degradation. The number of newly incurred dead and bad pixels is negligible since the start of operations. Assuming linear degradation of various component, the SWIR module is expected to keep performing within expected parameters for the full operational lifetime.