달 탐사 및 유인 활동 수요의 증가로 인해 달 환경에서 안정적인 항법 제공의 필요성이 커지고 있으나, 지구 기반 Global Navigation Satellite System (GNSS)만으로는 달 전역에 항법신호를 송신하기 어렵 다 는 한계가 존재한다. 이를 보완하기 위해 다수의 초소형 항법위성을 달 궤도에 군집 배치하여 전 지점에 독립적인 항법 신호를 제공하는 Lunar Navigation Satellite System (LNSS) 기술이 연구되고 있다. 본 연구는 Elliptical Lunar Frozen Orbit (ELFO) 궤도를 통해 LNSS 임무를 수행하는 6U 큐브위성 기반 자세제어 시스템을 제안한다. 달 궤도 환경은 자기장이 부재하기 때문에 반작용 휠과 추력기를 구동기 로 적 용하였으며, 정밀한 자세제어와 추력기 연료 소모를 최소화하는 휠 모멘텀 관리를 수행한다. 제안한 알고리즘은 MATLAB 기반 Software-In-the-Loop Simulation (SILS) 환경에서 구현하였다. 본 연구를 통해 6U 큐브위성의 제어 알고리즘 성능을 검증하고, LNSS 임무 수행가능성을 확인하였다.

Software-in-the-Loop Verification of a 6U CubeSat Attitude Control System for LNSS

Hyung-Goo Lim, Hyewon Park, O-Jong Kim*

Recent global interest in lunar exploration has been rapidly increasing, with various countries actively carrying out their missions. The United States is advancing the Artemis program to establish sustainable human lunar exploration, while South Korea has successfully operated the Korea Pathfinder Lunar Orbiter (KPLO). In addition to these activities, the inability to utilize Earth's Global Satellite Navigation System (GNSS) on the lunar highlights the need for an independent Lunar Navigation Satellite System (LNSS). The LNSS considered in this study deploys eight CubeSat-based navigation satellites in each of two Elliptical Lunar Frozen Orbit (ELFO) planes, designed to provide stable navigation services across the lunar surface. This study performs Software-In-the-Loop Simulation (SILS) of the 6U CubeSat attitude control for LNSS. The Attitude Determination and Control System (ADCS) combines the thrusters and reaction wheels for attitude control, and uses a strategy to minimize the use of the thrusters by continuously dumping the accumulated wheel momentum. The simulation considers the characteristics of the lunar environment. The absence of a magnetic field makes the use of magnetic torques impossible. And gravity is only about a sixth of the Earth, and there is no aerodynamic drag due to the absence of the atmosphere. Also, periodic eclipses caused by the relative positions of the Sun, Earth, and Lunar impose restrictions on sun sensor availability. Through simulations, we verify the performance of the ADCS algorithm of CubeSat and determine the possibility of performing the LNSS mission.

Keywords: attitude determination and control system, LNSS, wheel momentum dumping

Speaker 임형구 세종대학교