ATTITUDE DETERMINATION FOR THE CUBESAT SPLASH USING A MAGNETOMETER AND SUN SENSOR

The estimation and control of a satellite’s attitude are critical for mission success, ensuring precise orientation for power generation, communications, and payload operations. This paper presents a comprehensive comparative study of three attitude-determination methods—Quaternion Estimator (QUEST), first-order Alpha Filter, and Extended Kalman Filter (EKF)—applied to the conceptual CubeSat SPLASH. MATLAB simulations of magnetometer, digital sun-sensor, and rate-gyro measurements, each corrupted by realistic noise profiles, were conducted under a 400 km equatorial orbit scenario. Performance metrics include root-mean-square (RMS) attitude error, convergence time after a step disturbance, and onboard computational time. Results show that the Alpha Filter, while computationally lightest, yields the highest steady-state error (≈0.5° RMS) and slowest disturbance recovery; QUEST achieves moderate accuracy (≈0.2° RMS) with minimal drift but requires simultaneous dual-vector measurements; and the EKF attains the best overall performance (≈0.1° RMS) at the cost of increased processing effort. Detailed analysis of error time histories and sensitivity to sensor noise is provided. These findings inform the selection of attitude filters for CubeSat missions, balancing precision needs against processing constraints.