Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2017, Vol. 14, No. 2, pp. 9-23
Geometric calibration of high-precision star tracker by starry sky
P.S. Smetanin
1 , G.A. Avanesov
1 , R.V. Bessonov
1 , A.N. Kurkina
1 , A.V. Nikitin
1 1 Space Research Institute RAS, Moscow, Russia
Accepted: 14.03.2017
DOI: 10.21046/2070-7401-2017-14-2-9-23
This work is devoted to experimental study of a high-precision star tracker calibration technique by real astronomical objects – stars on the celestial sphere. The high-precision optical head (OG-VT) based on the OZK-125/4 lens and CMOS image sensor CMV20000 has been used in experiments and the obtained images of the celestial sphere stars are analyzed. An algorithm of star tracker geometric calibration is considered.
Recommendations are given for selecting starry sky frames suitable for calibration and the concept of ratio of stars filling the field of view is introduced. During the experiments, the following star tracker calibration parameters are defined step by step: principal point coordinates, focal length and generalized distortion function. In addition, the orientation angles are calculated. The calibration parameters dependence on temperature, as well as influence of determining the focal length and accuracy of principal point coordinates on the accuracy of determining generalized distortion function are considered. An experiment on finding dependence of of estimation accuracy of generalized distortion function on stars’ spectral classes has been conducted.
The resulting accuracy of OG-VT calibration parameters as well as obtained orientation parameters are estimated. Theoretical and experimental calibration parameters are compared. Relative star angular positions on night sky would be known with high accuracy, thus providing for an advantage of the proposed star tracker calibration technique, compared with others methods using ground optical equipment.
Keywords: geometrical calibration, distortion, orientation parameters, star tracker, focal length, principal point, stellar classification, temperature, accuracy estimation
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