Gyroless Nanosatellite Attitude Estimation in Loss of Sun Sensor Measurements

The paper introduces gyro-free attitude estimation methods for sun and eclipse phases. First of all, traditional and nontraditional attitude estimation approaches are investigated relying on sensor measurements from magnetometer, and sun sensor. For the nontraditional approach, vectors are placed in Wahba's problem and the loss function is minimized by Singular Value Decomposition (SVD) method. The coarse attitude information and their variances from SVD are used in the extended Kalman filter (EKF) as linear measurements in order to estimate the satellite's attitude and angular rate. With using the same filtering parameters and initial conditions in traditional EKF, a comparison is made for the sun phase of the orbit. However, for the eclipse period (in loss of Sun sensor measurements), two additional methods are introduced as the prediction method, and traditional EKF based on only magnetometer measurements. An accuracy performance analysis is performed, for different phases, a switching algorithm is used for better attitude and rate estimation.