Attitude Determination Algorithm Using Earth Sensor Images and Image Recognition

This paper describes a new algorithm to determine the attitude of micro-/nano-satellites using an Earth sensor. For recent micro-/nano-satellites, the requirements for attitude determination accuracy are becoming more stringent, despite its limited volume. Since Earth sensors have the advantage of smaller size, some studies have presented using them as attitude sensors; however, they could not achieve fully automatic processing in real-time. Therefore, we have developed an algorithm that effectively combines geometrical consideration and image recognition technology, thus realizing high autonomy, robustness, and real-time processing. The validity of this algorithm is confirmed through ground experiments. The algorithm operates at a rate of 0.2 Hz and achieves an accuracy of 0.1–1 deg, which is similar to the accuracy of a coarse sun sensor. Furthermore, it is capable of determining the three-axis attitude using only an Earth sensor and a GNSS receiver for position information. This study proves that the bus equipment required for attitude determination systems in micro-/nano-satellites can be reduced, thereby contributing to increased design freedom.