Study On Several Key Technologies For High-accuracy Star Sensor

Star sensor is a high precision instrument with star as frame of reference to achieve the three-axis attitude measurement in inertia space. The development of space remote sensing and reconnaissance, and the requirement of astronomical observation put forward the demand of extremely high accuracy measuring instrument in inertia space. The star sensor can meet these requirements. As foreigners have already realized the transition of star sensor in sub-second level, the investigation of high accuracy star sensor has practical significance.The image sensor has a great influence on the accuracy of star sensor, and the low frequency errors of star sensor are mainly due to the optical system. This paper carries out research on several key technologies including the detection performance of large frame array APS image sensor under novel exposure mode, the characteristic and compensation of noise and errors, the impact of optical aberrations to the precision of sub-pixel centroid subdivision and the optical design method of high accuracy star sensor. The main work of this paper are summrized below:1) The logic and relevance of the main technical parameters of star sensor are presented including focal length, field of view, selection of threshold star magnitude and amount of detected stellar, accuracy of single star, integration time, frequency of data update, weight, size and power dissipation. The paper analyzes the characters of APS image sensor, and gives the detection ability, dynamic range, detection probability, field of view and threshold star magnitude under novel exposure mode.2) Analyzes the various influent factors of star sensor accuracy under rolling shutter exposure mode. Builds the model of how the detector noise influents the accuracy. Analyzes the measurement error under different exposure modes of APS image sensor. Analyzes how the exposure mode of rolling shutter influents the accuracy of centroid position. Analyzes the influence to the accuracy of stellar position under dynamic conditions. The model of centroid subdivision is modified and the method of accuracy compensation is given under dynamic coditions.3) Investigates how the optical aberrations influents the centroid position accuracy of hyperfine sub-pixel. Analyzes the difference between PSF model of diffraction-limited and ideal Gaussian function. Analyzes the difference and distribution of centroid position accuracy with different sizes of diffuse spot and window. Zernike is adopted to characterize the aberrations polynomial. Analyzes influence to centroid position accuracy and distribution of primary aberration.4) Investigates the optical system design method of high-accuracy star sensor. Describes the influence of stellar color temperature changes on the measurement accuracy. Establishes a selection model for the wavelength weight of optical system. A new athermal and achromatic method of optical system is presented. The optical design form, results and evaluation are given.5) Builds a high-precision star sensor test system based on APS image sensor. Carries out star measurement experiment inside laboratory and analyzes the experimental results.