Initial Operation Results of EQUULEUS ADCS: Wheel Unloading Strategies for a Deep Space 6U CubeSat
- Paper number
IAC-23,B4,8,3,x76180
- Author
Mr. Hirotaka Sekine, University of Tokyo, Japan
- Coauthor
Dr. Shunichiro Nomura, University of Tokyo, Japan
- Coauthor
Dr. Ryohei Takahashi, ArkEdge Space Inc., Japan
- Coauthor
Mr. Vinícius Nery, University of Tokyo, Japan
- Coauthor
Mr. Toshihiro Suzuki, University of Tokyo, Japan
- Coauthor
Mr. Riki Nakamura, University of Tokyo, Japan
- Coauthor
Dr. Shintaro Nakajima, Japan Aerospace Exploration Agency (JAXA), Japan
- Coauthor
Dr. Yosuke Kawabata, University of Tokyo, Japan
- Coauthor
Mr. Ryota Fuse, University of Tokyo, Japan
- Coauthor
Mr. Kota Miyoshi, Japan Aerospace Exploration Agency (JAXA), Japan
- Coauthor
Mr. Akihiro Ishikawa, University of Tokyo, Japan
- Coauthor
Dr. Satoshi Ikari, University of Tokyo, Japan
- Coauthor
Prof. Ryu Funase, Japan Aerospace Exploration Agency (JAXA), Japan
- Year
2023
- Abstract
EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) is one of ten CubeSats launched by NASA SLS (Space Launch System) in November 2022. The primary mission of this deep space 6U CubeSat, developed by JAXA and the University of Tokyo, is to demonstrate orbit control technology. It is expected to take more than a year to achieve EML2 (the second Earth-Moon Lagrange point) injection while performing multiple lunar swing-bys and orbit control. After reaching EML2, EQUULEUS will continue scientific observations while maintaining a halo orbit. This paper summarizes the initial results of EQUULEUS ADCS operations, specifically focusing on wheel unloading strategies for a 6U CubeSat in deep space. The 6U CubeSat has small-sized reaction wheels and thus limited angular momentum storage capacity, making it essential to effectively manage angular momentum to sustain three-axis attitude control in a deep space where disturbance torque accumulates. The available fuel for angular momentum management is severely limited due to the size of the spacecraft. This is particularly challenging for EQUULEUS as orbit control is its primary mission, requiring a significant amount of fuel. Furthermore, angular momentum must be strictly managed to guarantee sufficient power generation and maintain spacecraft temperature, even after transitioning from the three-axis control mode to the tumbling mode in case of low battery voltage. Consequently, the EQUULEUS operation efficiently manages angular momentum by utilizing orbit correction control opportunities and SRP (Solar Radiation Pressure). This paper categorizes the angular momentum management method into three phases: 1) Delta-V operation for major orbit changes, 2) TCM (Trajectory Correction Maneuver) operation for minor orbit correction, and 3) cruising. In the Delta-V operation, it is important to continuously perform propulsion operations within a limited time to achieve the mission. Setting an appropriate angular velocity threshold enables the automatic selection of thrusters for unloading while maintaining continuous propulsion system operation. In TCM operations, thruster selection is pre-planned based on the predicted required velocity increment, leading to more robust angular momentum control against uncertain thrust generation. During cruising, utilization of changes in the sun's direction in the body frame enables unloading using SRP. This paper shows the on-orbit results of these methods, and these unloading strategies are applicable for future deep space CubeSat explorations.
- Abstract document
- Manuscript document
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