Utilizing digital micromirror devices for spacecraft attitude control with initial diffraction effects for varying incidence angles

This paper investigates the application of Digital Micromirror Devices (DMDs) to spacecraft attitude control through the modulation of solar radiation pressure (SRP). By reconfiguring the orientation of individual micromirrors, a DMD functions as a spatially reconfigurable reflective surface that can shape both the normal and in-plane components of SRP, thereby enabling propellant-free, three-axis momentum management. An overview of the SRP force and torque model as applied to DMD-based surfaces is presented, followed by an initial extension of the model to account for diffraction effects arising from the periodic micromirror geometry. When uniformly commanded, a DMD may be approximated as a blazed grating, producing wavelength- and incidence-angle-dependent angular redistribution of reflected solar energy that departs from purely specular reflection. Using a geometric projection model and a first-order diffraction approximation, the angular width of the dominant diffraction lobe is estimated as a function of incidence angle across representative wavelengths in the solar spectrum. The results indicate that diffractive effects become increasingly significant at shallow incidence angles and longer wavelengths, reducing the effective normal SRP component and increasing the in-plane component, thereby supporting diffraction as a viable physical mechanism for augmenting SRP-based spacecraft attitude control using DMDs.