A Star Image Pre-processing Method of Star Sensor Based on Sobel Operator

star sensors are vulnerable to the interference of stray light when working in space. It is difficult to extract the coordinates of the fixed star image from the star image by means of the centroid method after the binaryzation of star image. To solve the above problem, a novel star image pre-processing method for extracting start image coordinates of star sensor based on Sobel operator is presented in this paper. Firstly, Sobel operator is used to calculate the gradient of all pixels in the star image. All pixel gradients larger than the threshold are retained as a new star image and then the new star image is used as the template to extract the fixed star image from the original star image by the centroid method. Because the stray light interference signals behave as slow signals in the star image, the gradient calculated by these signals is very small, the new star image calculated with Sobel operator is only the fixed star image. The proposed method has good robustness because it can eliminate the stray light interference signals in star image and improve the accuracy of extracting fixed star image coordinates.

Conclusion

For traditional image processing methods that are difficult to effectively extract stellar coordinates from star maps under stray light interference, this paper proposes a Sobel operator based method for extracting stellar image coordinates from star sensors. Based on the experimental simulation results, the following conclusions can be drawn:
1) The method proposed in this article can effectively extract the contours of stars that have not been submerged by stray light. The new star map, calculated by the Sobel operator, only contains the stellar image, thus achieving the goal of eliminating interference signals from stray light in the star map.
2) Combined with image morphology processing, the accuracy of star point centroid extraction has been greatly improved.
3) As the intensity of stray light increases, its coverage in the star map increases, and the number of submerged stars increases. Therefore, this method is suitable for extracting stars that are not completely covered by stray light.
The simulation results processed by the algorithm in this article show that the method has good robustness and universality.