Given the complexity and specificity of star sensors, it is difficult to conduct a thorough research on them in the short term. Therefore, this article mainly introduces some key technologies (hardware and software aspects) of star sensors. Mainly including:
As the CCD imaging part is the foundation of the subsequent work of the star sensor, the quality of the star map also determines the quality and accuracy of the subsequent work, so it is one of the key technologies of the star sensor. This section studies the principles of CCD imaging and image signal transmission, analyzes the role of relevant timing drive control signals in the entire image transmission process, determines the design concept of using a state machine to generate relevant timing drive signals, and adopts VHDL language as the hardware description language to describe timing drive signals.
As the first step in subsequent image data processing, its importance is reflected in the fact that high-precision and fast star coordinate extraction can provide higher accuracy for subsequent algorithms, improve the accuracy of output attitude, and improve the overall attitude update rate. The main content of this section is to analyze and study the key steps of star point extraction, including threshold calculation, star map threshold segmentation, connected domain analysis, interpolation and subdivision positioning algorithm of star point coordinates, and propose an improved threshold centroid algorithm to improve the extraction accuracy.
Attitude calculation is the final step in the entire star sensor workflow, and its calculation results determine the accuracy and update speed of the star sensor attitude. This article studies static determination algorithms and dynamic estimation algorithms for attitude determination, and compares typical static determination algorithms through simulation to obtain the algorithm with the best relative performance. In terms of dynamic algorithms, predictive Kalman filtering is introduced into the attitude estimation of star sensors and verified through simulation. And relevant research was conducted on the selection of weight parameter matrices.
(4) System accuracy analysis and experimental calibration methods.
This section mainly analyzes the main determining factors of star sensor accuracy, analyzes their sources and influencing factors, and introduces various error calculation methods and total error calculation formulas. Introduced the indoor and zenith testing and calibration methods, and finally conducted accuracy simulation tests on the entire star sensor system.
Due to the high precision and complexity of its structure, the absolute accuracy of star sensor systems is determined by the comprehensive technology of various aspects. This article only provides relevant introductions to a few of these aspects. There is still a lot of room for improving the performance of star sensors. For example, the CCD timing drive can be directly designed and implemented using ASIC circuits, without the need for programmable logic devices. This can reduce resource utilization and save energy consumption. In terms of dynamic attitude estimation, the predictive Kalman algorithm can be further improved to simplify calculations and further improve the attitude update rate.
The mainstream star sensors and the vast majority of photoelectric sensitive devices with high precision requirements for star sensors are CCD, and the exploration of their technology still has practical significance.
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TY-Space Technology (Beijing) Ltd. is professional focusing on advanced attitude optical sensors, especially Star Trackers for space industry.
