New Type Reflective Optical System Design For A Star Sensor

Star sensors have been widely used on spacecrafts because of the advantages of their high degree accurate allocation. They are also the attitude sensors that enable self-allocation nowadays, so the star sensors have extensive development potential. Optical system, as a part of the star sensor, is operating important function. The large D/f and wide spectral coverage of the system are the trends of development. The text is done with the thoughts above.First and foremost, the development states of the star sensors abroad have been introduced. Then, the conditions in our country to that abroad are compared, and the trends of the star sensors all over the world have been mastered. So, it supplies a general direction of the selection of CCD and the basis structure of the optical system.Consequently, a new style optical system with"reflective lens"is designed. After comparing with other transmission-type optical systems, this paper summaries some advantages of the system: There is no chromatic aberration or second order spectrum; it is easy to reject stray light; it can be light weighted and so on.Thirdly, according to the parameters of the optical system which has been calculated, a coaxial-three-mirror system with a secondary image is designed. Then, the image quality is evaluated and optimized with CODE V, a kind of software of optical design. In order to meet the special requirement of the star sensor, it is necessary to de-focus the optical system. Additionally, a plan of tolerance distribution to supply measurements of tolerances of treatments and alignments is completed. Also, optical efficiency is calculated, and they all meet technical requirements.Finally, according to practical situation of space, it is necessary to design a baffle using LightTools, to reject off-axis stray light which influents optical system and image qualities. The ability of rejecting stray light is enhanced by designing a main mirror baffle and a Lyot stop. So, the length of the baffle is reduced, which also meets the needs of the system. The whole optical system is packaged after designing, to reduce the influence out of space to mirrors.