Lunar-Intrusion Resilient Calibration Algorithm Developed for a Compact Atmospheric Microwave Sounder (CAMS) Onboard TY-16 Small Commercial Satellite
Abstract
The compact atmospheric microwave sounder (CAMS) aboard the commercial TianYan-16 satellite is a cross-track scanning radiometer with two separate cold-space view on its left and right sides. During on-orbit operation, the Moon regularly intrudes into one deep-space view (DSV), producing abnormal cold-space counts and undermining the instrument’s two-point calibration accuracy. This work presents an adaptive method for detecting and correcting lunar contamination leveraging the linear correlation between dual DSV measurements. First, uncontaminated observations with stable radiation are extracted from long-term datasets to build an inherent linear mapping model between the two DSVs and solve for fixed conversion coefficients representing their natural radiation offset. Two discrimination indicators are then applied for contamination detection: one identifies single-field radiation anomalies via sequence dispersion, while the other monitors the relative deviation between bilateral DSV data, which rises drastically once lunar intrusion (LI) occurs. Combined indicators automatically label contaminated samples. Rather than simple data replacement, the established linear coefficients are used to reconstruct the uncontaminated radiometric values of the corrupted DSV from the unaffected measurements for high-precision correction. The reconstructed DSV data are subsequently adopted for on-orbit two-point calibration. Requiring no auxiliary data, this method handles both mild and severe lunar interference to maintain long-term calibration stability and improve data quality. Validated against September 2025 CAMS Level-1 data with severe LI, the approach reduces the residual standard deviation (STD) of contaminated cold-space counts by 74%–92%. Channel-wise corrections reach tens of kelvin across channels, peaking at about 27 K in the 183.31-GHz water vapor channel. The dual-DSV scheme effectively suppresses lunar-induced anomalies and provides a reliable calibration solution for future satellite microwave missions.