High-precision Astrometry of Saturnian Major Satellites: Halo Reduction and Optical Filter Evaluation

Abstract

High-precision astrometry of planetary satellites is important for refining ephemerides and supporting deep-space exploration missions. We apply the Bilateral-filtered Single-Scale Retinex with Gaussian regularization (BSSR-Gaussian) method to 140 CCD images of Saturn obtained at Yunnan Observatory and evaluate the performance of five Bessell filters (U, B, V, R, and I) together with a clear configuration for optimizing ground-based observations. The BSSR-Gaussian method significantly improves the astrometric performance compared with traditional Median Filtering (MF). The number of valid observations increases by 15.7% on average, while the standard deviation of the (O − C) residuals in right ascension and declination decreases by 28.6% and 31.2%, respectively. Among the tested filters, the I band achieves the highest positional accuracy under long exposures, whereas the R band provides the most stable performance under varying observing conditions. The U, B, and V bands, as well as the clear configuration, are unsuitable for high-precision observations because of insufficient reference stars or severe halo contamination. Our results confirm the general applicability of the BSSR-Gaussian method for halo removal in observations of giant-planet satellites and provide practical guidance for future ground-based astrometric observations.