Zero-Speed Crossing Avoidance with Three Active Reaction Wheels using Set-Point Angular Momentum Management

Reaction wheels (RW) are common actuators for attitude control of three-axis stabilized satellites. By exchanging momentum with the spacecraft's body, a set of three non-planar RW is able to ensure the off-nadir fine pointing capabilities of agile high-resolution imaging satellites. Nonetheless, due to stiction, RW can cause considerable attitude jitter when their angular velocity is close to zero. This paper proposes a method to analyze the maximum off-nadir pointing angles that are allowable without causing zero-speed crossing for a spacecraft using only three active RW. In sequence, by applying this method for a sun-synchronous mission, it is shown that angular momentum management can be used to give the satellite an adequate roll slewing margin by placing the reaction wheel momentum set point in an appropriate position. This method can be applied to any mission that relies on three active RW and requires high pointing stability.