Estimating Sun Vector Based on Limited In-Orbit Data

Abstract

This paper introduces an attitude and orbit determination system, in particular a sun vector determination algorithm, for HORYU-IV nano-satellite by Kyushu Institute of Technology (Kyutech). Usually, nano-satellites cannot use sensors with high specs because of limited budget and onboard space. In order to achieve the required accuracy of attitude determination, estimation algorithms combining different sources of attitude information should be used. One of the HORYU-IV missions has required sun vector information. In order to detect the sun angle, six sun sensors, which have originally been designed and developed by the authors, and five solar panels have been used. However, due to the narrow field of view and to the saturation property of these sensors, the duration of sun detection is quite limited. At a non-detection period, a gyro sensor is used in order to propagate the attitude. However, the sensor has the bias error in its measured value. Hence, the Extended Kalman Filter has been used in order to estimate the sun vector and the bias error of gyro sensors. A simulation result shows that the algorithm can estimate the sun vector in 1deg accuracy.