Determination of the optical system parameters for a CMOS APS based star sensor

CMOS APS based star sensor is a new generation of attitude sensor produced to keep up with the development of aerospace technology.Determination of the optical system parameters such as the spot shape and size,the effective aperture,the field of view and the focal length is the precondition to perform optical design of the star sensor.This paper gives the analysis and the calculation of these parameters based on a selected CMOS APS.The spot shape and size are determined to minish the sub-pixel centroiding error caused by the distortion of the point spread function due to the pixel sampling effect of the CMOS APS.The effective optical aperture is related to the magnitude threshold of the stars that can be detected by the sensor.So the aperture can be determined through the energy calculation from the radiation of the objects to the response of the sensor.The determination of the field of view and the focal length needs firstly to fulfill the probability of navigation stars capture for the realization of the autonomous star recognition in the whole sky,and secondly to take the relative errors into consideration.