尋星儀(Star Tracker)是衛星與太空載具之姿態判斷系統的最關鍵的元件。衛星的主要性能規格受到尋星儀性能的限制極大。大至地球同步通訊衛星小至立方衛星，尋星儀均是衛星的標準配備。而尋星儀中的核心零組件之一就是其鏡頭。
本論文將對尋星儀鏡組優化設計，考慮項目包括場角、成像品質、光般大小等，最終設計了一個小型化、輕量化，同時考量加工成本以及操作性的尋星儀。除可大幅降低未來衛星任務的經費，更是對台灣未來衛星任務的自主性極為重要，有效提升太空領域的研究能量。

The study on the design and optimization of the satellite star tracker lens system
Po-Yu Chen
Advisor: Shu-Chu, Ph.D.
Department of Physics, National Cheng Kung University
SUMMARY
Star trackers are the essential unit equipped on satellites for monitoring posture. The performance specifications of the satellites are greatly limited by the star trackers lens. This paper describes how to use geometric optics aberration as tools, to design satellite star tracker lens. Finally, we design a satellite star tracker lens that is miniaturized, lightweight, and commercially available, which can be properly operated under the On Semiconductor HAS2 CCD chip.

Key words: star tracker, optical system design

INTRODUCTION

In the 21th century, research in outer space has already been a popular field. Most of the studies are carried on varies artificial satellites. Star trackers are the essential unit equipped on satellites for monitoring posture. The performance specifications of the satellites are greatly limited by the star trackers. And, the performance of the star trackers is heavily relying on lens. In this article, we will demonstrate the progress of the lens optimization and design.

MATERIALS AND METHODS

In geometric optics, the ideal optical system at any point on the object plane that emits the same beam through the optical system, converges a point on the imaging plane, and the arrangement of the image points on the image plane The arrangement of the source points on the plane is in an equal proportional relationship. For wave optics, the ideal imaging system should perfectly present the wave front of the object plane on the image plane.
Aberration is the difference between the actual imaging and the ideal of the optical system. The aberration can be described by the ray offset of an ideal imaging point or by the wave front offset of the ideal reference light. Often such an offset is related to the aperture and the angle of view. For example, the imaging positions of the ray incident at different apertures are different, the imaging magnifications of the incident light at different angles of view are different, etc. This paper describes how to use these offsets as tools, to design satellite star tracker lens.

RESULTS AND DISCUSSION

The ultimate goal of this thesis is to design a commercially available star tracker, and there are two elements to avoid when discussing commercialization. One is cost, and the other is user convenience. In terms of practicality, if the mirror is not sensitive to the change in curvature in the tolerance analysis, the difference in imaging effect will not be too large, and the cost of the mold can be saved in production. In terms of weight, the density of the K9 glass is 2.21g/cm3, and the weight of the lens part is only 41.9g, which is in line with the assembly requirements of the mirror.

CONCLUSION

This paper designs a satellite star tracker lens that is miniaturized and lightweight, while considering processing costs and operability. It can reach a field of view of 15 degrees and the maximum distortion of the whole field is less than 0.5%. The spot size of the whole field is less than 128μm, which can be properly operated under the On Semiconductor HAS2 CCD chip.

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