Modeling Analog Sun Sensor Current Output

This paper presents the derivation of a new sun sensor model and compares the predicted output to unit test data. The new model has been derived for a generalized rotation of the sensor with respect to the principal axes of the spacecraft. The modeling of the variation of the space output as a general function of the kinematics of the rotation of the sensor and an arbitrary sun location was initially solved using spherical geometry. However, the execution time required for this solution was unacceptable for the strict time constraints of real-time simulation. Therefore, a second method of modeling was derived in cartesian space, which proved to be a concise solution well suited to real-time simulation. This new analog sun sensor model generates predicted output for given sun elevation and azimuth, and sensor orientation angles based on a general analytical function. By varying the sensor sweep angle, the user can construct a current pulse that is accurate over the full range of the sensor.