Optical Design For Catadioptric Star Sensor With Large Aperture

As a high-precision attitude measurement instrument,the optical system is the most important part of the star sensor.It is mainly used to measure the attitude of spacecraft by imaging the target star,which is widely used in satellite and other fields.However,with the development of space technology,the requirements for the attitude accuracy of spacecraft are more and more high.It is necessary to detect stars with higher star as reference target.In order to improve the detection ability of star sensor,it is required that its optical system should be able to reduce distortion and chromatic aberration as much as possible on the basis of a wider spectral range and a larger pupil diameter.In this paper,an optical system of a large aperture,catadioptric star sensor is designed,and the energy distribution of the star point is analyzed.Finally,through the analysis of the experimental results of the dispersion spot test,it is verified that the optical system designed can meet the imaging requirements.Firstly,the development of star sensors at home and abroad and the optical system of large aperture star sensors are introduced.Based on the demand of star sensor for star detection,the detection ability of star sensor is analyzed from the aspects of star signal energy,CCD star energy,signal-to-noise ratio calculation and star detection probability calculation,and the interrelation between the main parameters and technical indexes of star sensor optical system is studied,so as to determine the field of view,aperture,central wavelength and other parameters of the designed optical system And the size and distortion of diffusion spots.Secondly,this paper focuses on the design and image quality evaluation of the optical system of the large aperture star sensor for the detection of 15 stars.In this paper,an improved Cassegrain system,a set of aperture correction spherical lens and a set of field correction spherical lens are used to design a star sensor catadioptric optical system with spectral range of 450-950 nm,half field of view of 1.4~o,aperture of 250 mm,focal length of 425 mm,which can correct astigmatism,field curvature and distortion.Based on the primary aberration theory,the initial structural parameters of the system are optimized by ZEMAX software.The secondary shielding ratio of the optical system is 0.43,80%of the energy of the imaging point is concentrated in 30?m,the maximum distortion is 0.081%,the optical modulation transfer function(MTF)is greater than 0.75 at the Nyquist frequency of 33.3 lp/mm,and the maximum magnification color difference is-1.67?m.Among the 20 Monte Carlo analysis results,the performance function of the 13th structure is the best,which is 4.97516?m,and the performance function of the 20th structure is the worst,which reaches 7.79957?m.The above indexes meet the imaging requirements of star sensor for 15 star dark star detection.The above indexes meet the imaging requirements of star sensor for detecting 15 stars.Finally,through the analysis and simulation of the star image mathematical model of star sensor,it is theoretically verified that the Gaussian energy distribution model is suitable for the star point energy distribution of star sensor.The results show that 80%of the energy of star image points accounts for the size of diffuse spots within 2×2 pixels(30?m).The designed optical system of large aperture star sensor meets the requirements of dark star detection.