Passive Solar Homing Control Using an Angle-Responsive Tunable Optical-Property Device

This study presents the angle-selective tunable optical-property (ASTOP) device that passively modulates optical property with incident solar angle to produce controlled solar radiation pressure (SRP) torque. When mounted on spacecraft with centrally located solar-array panels, ASTOP restores a nonzero torque arm effect and enables passive solar homing-monotonic convergence of the sun angle without sustained precession. Design requirements are derived from the generalized spinning sail model, and long-duration attitude simulations confirm convergence within ten days with an initial spin-axis misalignment. The ASTOP device offers a practical fuel-free attitude-control solution via SRP.