Calibration of the intrinsic parameters of the digital camera of a star tracker based on ground-based observations of stars, taking atmospheric refraction and aberration of light into account.
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| Title: | Calibration of the intrinsic parameters of the digital camera of a star tracker based on ground-based observations of stars, taking atmospheric refraction and aberration of light into account. |
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| Authors: | Vasilyuk, Nikolay N.1 (AUTHOR) nik-vasilyuk@yandex.ru, Nefedov, Grigorii A.2 (AUTHOR), Sidorova, Ekaterina A.2 (AUTHOR), Shagimuratova, Natalya O.2 (AUTHOR) |
| Source: | Measurement Techniques. Nov2023, Vol. 66 Issue 8, p593-609. 17p. |
| Subjects: | Digital cameras, Refraction (Optics), Star observations, Surface of the earth, Stellar atmospheres, Measurement errors |
| Abstract: | The problem of the individual calibration of five elements of the intrinsic orientation of the digital camera of a star tracker is examined: the focal distance of the objective, two coordinates of the principal image point, and two second order coefficients of second-order radial distortion. These elements of the internal orientation form a set of parameters for a mathematical model of digital images of stars taken by a star tracker camera. Stars observed from the earth's surface by the camera being calibrated are used as the calibration test object. The coordinates of the stars are cataloged with very high accuracy, which made it possible to avoid complicated calibration equipment and reduce the calibration problem to a particular problem of digital processing of images of stars. It is shown that the effects of distortion of stars observed from the earth's surface owing to velocity aberration and atmospheric refraction can be taken into account by introducing distortions in the directional vectors of stars taken from the star catalog. Two approaches to solving the calibration problem are considered which take the unknown orientation relative to the earth of the camera to be calibrated into account in different ways. It is established experimentally that the two approaches yield the same results. The discrepancy in the results of the calibration measurements after calibration is reduced by a factor of 32 to a value on the order of the unremovable angular error in determining the visible position of a star in a turbulent atmosphere. The results of an individual calibration of the elements of internal orientation of the camera are used in the program software for the star tracker to correct the systematic error in the measurements of the orientation based on the stars. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | The problem of the individual calibration of five elements of the intrinsic orientation of the digital camera of a star tracker is examined: the focal distance of the objective, two coordinates of the principal image point, and two second order coefficients of second-order radial distortion. These elements of the internal orientation form a set of parameters for a mathematical model of digital images of stars taken by a star tracker camera. Stars observed from the earth's surface by the camera being calibrated are used as the calibration test object. The coordinates of the stars are cataloged with very high accuracy, which made it possible to avoid complicated calibration equipment and reduce the calibration problem to a particular problem of digital processing of images of stars. It is shown that the effects of distortion of stars observed from the earth's surface owing to velocity aberration and atmospheric refraction can be taken into account by introducing distortions in the directional vectors of stars taken from the star catalog. Two approaches to solving the calibration problem are considered which take the unknown orientation relative to the earth of the camera to be calibrated into account in different ways. It is established experimentally that the two approaches yield the same results. The discrepancy in the results of the calibration measurements after calibration is reduced by a factor of 32 to a value on the order of the unremovable angular error in determining the visible position of a star in a turbulent atmosphere. The results of an individual calibration of the elements of internal orientation of the camera are used in the program software for the star tracker to correct the systematic error in the measurements of the orientation based on the stars. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 05431972 |
| DOI: | 10.1007/s11018-023-02272-z |
