In the work reported in this paper, a lost-in-space star pattern identification algorithm for agile spacecraft was studied. Generally, the operation of a star tracker is known to exhibit serious degradation or even failure during fast attitude maneuvers. While tracking methods are widely used solutions to handle the dynamic conditions, they require prior information about the initial orientation. Therefore, the tracking methods may not be adequate for autonomy of attitude and control systems. In this paper a novel autonomous identification method for dynamic conditions is proposed. Additional constraints are taken into account that can significantly decrease the number of stars imaged and the centroid accuracy. A strategy combining two existing classes for star pattern identification is proposed. The new approach is intended to provide a unique way to determine the identity of stars that promises robustness against noise and rapid identification. Moreover, representative algorithms implemented in actual space applications were utilized as counterparts to analyze the performance of the proposed method in various scenarios. Numerical simulations show that the proposed method is not only highly robust against positional noise and false stars, but also guarantees fast run-time, which is appropriate for high-speed applications.

In this study, a pioneering approach is introduced to elevate the performance of angular rate estimation in scenarios where gyros are not available. Within situations involving angular velocities, star observations exhibit notable variations in centroid accuracy based on their brightness. The critical aspect is the dispersion of starlight across multiple pixels due to the movement of the sensor during the exposure time. These effects culminate in the blurring of star intensity, resulting in the degradation of centroid accuracy. This phenomenon is particularly accentuated in dim stars with a low signal-to-noise ratio. Therefore, to enhance the performance of angular rate estimation, it is imperative to integrate these accuracy differences into the estimation process. The proposed algorithm originates from the idea of detecting faults in parity space, aiming at fault detection and isolation. Stars observed by the star sensor are considered redundant to each other and are used to identify stars with unusually large errors. It is observed that when the proposed method is applied, there is an approximate 40% reduction in the average RMSE of the estimated angular velocity compared to when quality is not considered at all. Additionally, an improvement of around 9% is noted compared to simply excluding values detected as faults.

우주기술과 응용(Journal of Space Technology and Applications; J. Space Technol. Appl. 이하 JSTA )은 한국의 우주과학 및 우주 응용 분야에서 가장 권위 있는 학술단체인 한국우주과학회에서 Journal of Astronomy and Space Sciences 와 더불어 발행되고 있는 공식적인 정기 간행물이다. JSTA 는 2021년 5월 창간호를 시작으로 연 4회 분기별로 발간되고 있으며, JSTA 의 논문과 기고문 은 한국어 또는 영어로 게재 가능하며, 각 논문과 기고문에는 고유의 DOI가 부여된다. JSTA 에 게재 되는 모든 논문과 기고문은 Open Access 정책에 따라 JSTA 홈페이지(https://www.jstna.org)를 통해 누구나 전문을 무료로 열람할 수 있다.

In this study, preliminary trajectory design for debris removal in low Earth orbit using solar sails is explored. Emphasis is placed on regions below 1000 km altitude, where the debris population is rapidly growing. The aim is to propose a mission concept capable of repetitively executing removal processes. The trajectory is intricately crafted, segmented into rendezvous, proximity operations, and deorbiting phases. Safety is prioritized by leveraging walking safety ellipses during proximity operations, ensuring efficient capture of targeted debris. Additionally, the feasibility and limitations of the mission concept are assessed through numerical simulations based on characteristic acceleration, a pivotal performance index of solar sails.