This letter relates to the development of satellite reflectarrays able to scan a single dual-polarized beam, based on monolayer resonating cells embedding digital microelectromechanical systems (MEMS). We study general topology constraints to be imposed on the elementary cell to ensure dual-polarized operation, minimal cross-polarization, and a reduced number of MEMS for a given phase resolution. It is shown that an element electrically invariant to a 90 degrees rotation is the most favorable one, and the theoretical considerations are verified by a design example under both normal and oblique incidence.