ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa


Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2022, Vol. 19, No. 6, pp. 41-49

Determination of the point spread function of an optical system of star trackers

N.A. Stroilov 1 , T.V. Kuptsov 1 , E.A. Bazina 1 , A.V. Nikitin 1 , Ya.D. Elyashev 1 , B.A. Yumatov 1 
1 Space Research Institute RAS, Moscow, Russia
Accepted: 01.12.2022
DOI: 10.21046/2070-7401-2022-19-6-41-49
During the alignment of the optical system of the star sensor it is necessary to evaluate images of single stars or point test objects. It is convenient to carry out such processing using point scatter functions (PSF). According to the function parameters, we can estimate the degree of stellar scattering, the quality of focusing of the instrument, as well as the aberrations of its optical system. If the focusing of the optical system is satisfactory, it is preferable to approximate the Eiri disk by a two-dimensional Gaussian distribution function. The criterion for defocusing the image in this case is the dispersion parameter of the function. However, the Gaussian function gives a rough approximation for defocused images when the maximum intensity falls on concentric rings. For optical systems with significant aberrations, the Gaussian function also gives coarse results, especially for images at the edges of the field of view. This paper compares three approximating functions: 1) a two-dimensional Gaussian function, 2) a rotation-aware Gaussian function, and 3) a function that is the sum of two two-dimensional Gaussian functions. The quality of approximation using the three PSFs has been compared. Their parameters, approximation quality and variance criteria have been compared and evaluated. It is shown that the dual function shows better results for all admissible aberrations and defocusing of the optical system over the whole image field.
Keywords: point spread function, PSF, image processing, focusing, adjustment, optical system, point, test object, star, approximation, approximation function, Gaussian function
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