Design Of A Catadioptric System For Star Sensors With Wide Field Of View

Star sensors measure the attitude of spacecrafts by identifying the stars in their field of view. This paper addresses the design of catadioptric systems for star sensors. Their reflective part is the Schwarzschiid configuration and the refractive part consists of three lenses made of the same material. This system has small central obstruction and a wide field of view. It can improve accuracy of star sensors. Only one surface is aspheric. This design reaches focal length 43.56mm, field of view 20? and relative aperture 1:1.2.Firstly, the content and the value of this study are introduced. It is set forth that to widen the field of view of optical system is very significant for improving its star identification success ratio and attitude measurement accuracy and decreasing the size of its guide star catalog. Also, the development and the optical system of star sensors are reviewed.Secondly, the establishment of the guide star catalog and its star identification technology are introduced. The working principle of star sensors is interpreted.Thirdly, the method of determination of its performances including its entrance pupil, focal length, field of view, spectral ranges, and center wavelength etc. Performance values about this design are presented. And the criterions for evaluation imaging quality are given in detail.Finally, the aberrations of reflective systems with two mirrors are analyzed. It is shown that the Schwarzschiid spherical system is better than Cassegrain and Gregorian spherical systems in terms of aberration correction. Aberrations can't be corrected perfectly since Schwarzschiid spherical systems have not enough parameters. Lenses are added to correct aberrations in order to widen the field of view. Lateral color aberration is calculated and the possilrility using lenses composed of the same refractive material is interpreted. Then the result is given and the performance of the obtained design is evaluated.