A calibration method of structural model for multi-FOV star tracker based on theodolite crosshair imaging

Abstract

Compared with the traditional single field of view (FOV) star tracker, the multi-FOV star tracker has the advantages of equal measurement accuracy on three axes and better dynamic performance. The measurement accuracy of a multi-FOV star tracker is directly determined by the accuracy of the structural model. However, existing structural model calibration methods cannot be applied to the high precision multi-FOV star trackers with large size and weight. To solve this issue, a calibration method of the structural model for the multi-FOV star tracker based on theodolite crosshair imaging is proposed. An imaging model of theodolite crosshair in star tracker is established which elaborates the relationship between the theodolite angles and the star tracker images. Multiple theodolites are utilized to pair each FOV of the star tracker. In each pair, through collecting the angles measured by the theodolite and the images captured by the star tracker, the rotation between the theodolite frame and the star tracker FOV frame could be solved. Additionally, the rotations between theodolite frames are obtained by mutual collimation of theodolites. Finally, the structural model which contains the rotations between the different FOV frames is acquired by merging the above rotations. Structural model calibration experiments of a multi-FOV star tracker with a large size and weight have been conducted. The experimental result indicated that the mean star angular distance error between FOVs was less than 10 arcseconds. The accuracy of the calibration result met the practical requirements. The proposed method is free from the influence of the size and weight of multi-FOV star trackers and maintains high calibration accuracy.