Sub-pixel Information Recovery in Crowded Stellar Fields with PhotSat Simulations

Abstract

The PhotSat mission will deliver high-cadence, all-sky photometry in the ultraviolet and visible bands, but its large detector pixel scale places the instrument in a strongly undersampled regime, limiting performance in crowded stellar fields. In this work, we investigate whether sub-pixel information naturally encoded in repeated Phot-Sat observations can be recovered through multi-frame image reconstruction. We develop a reconstruction pipeline based on the Drizzle algorithm and apply it to realistic Phot- Sat simulations. Using synthetic stellar catalogs with known ground truth, we compare a native-resolution aligned baseline with sub-pixel reconstructions to quantify improvements in effective resolution and source separability. Sub-pixel reconstruction reduces the effective PSF width by approximately 55% and increases the fraction of resolved stellar pairs from 17.6% to 57.8%, particularly at small angular separations, without introducing systematic flux biases. An application to simulated observations of the globular cluster 47 Tucanae provides qualitative validation under realistic crowding conditions. Despite intrinsic limitations, our results demonstrate that sub-pixel reconstruction can enhance the scientific return of PhotSat, representing a valuable scientific tool.