A Dual-Spinning, Three-Axis-Stabilized CubeSat for Earth Observations

e Microsized Microwave Atmospheric Satellite (Micro) combines two traditional control approaches: a dual spinner and a three-axis gyrostat. Unlike typical dual spinners, the purpose of Micro’s  cubesat bus and spinner assembly is to actuate a  cubesat payload, not to add gyroscopic stiffness. An orthogonal triple reaction wheel assembly will both counter the angular momentum from the payload and rotate the satellite’s bus about its orbit-normal vector to maintain bus alignment with the orbital frame, resulting in a zero-angular-momentum system. e payload spins about the spacecra velocity axis to scan successive swaths of the Earth. However, the cubesat form factor restricts the velocity axis to be along the spacecraminor axis of inertia. is orientation leaves the spacecra at a gravity-gradient-unstable equilibrium. Further, imperfect cancellation of the payload’s angular momentum induces nutation behavior. An extended Kalman lter is implemented on a -bit  microcontroller to combine gyroscope, limb sensor, and magnetometer data to provide attitude estimation accuracy of approximately  arcminutes. Simulations show that the reaction wheels can consistently maintain pointing to within  arcminutes for orbits above  kilometers with the payload rotating at . hertz.