A report discusses the problem of controlling the maneuvers of multiple spacecraft flying in formation and, more specifically, making the entire formation rotate about a given axis and synchronizing the rotations of the individual spacecraft with the rotation of the formation. Such formation flying is contemplated for mission in which the spacecraft would serve as platforms for long-baseline-interferometer elements and the synchronized rotations would be needed for slewing of the interferometers. Starting from (1) a particle model of the dynamics of the spacecraft formation, (2) a rigid-body model of the spacecraft-attitude dynamics, and (3) an assumption that one spacecraft would serve as the reference for the positions and orientations of the other spacecraft, the report presents a mathematical derivation of control laws for formation flying in the absence of gravitation and disturbances. A simplified control law suitable for implementation is also derived. Results of a computer simulation for three spacecraft flying in a triangular formation are presented to show that the control laws are effective.
This work was done by Fred Y. Hadaegh and Kenneth Lau of Caltech and Paul K. C. Wang of the University of California for NASA’s Jet Propulsion Laboratory.
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Synchronizing Attitudes and Maneuvers of Multiple Spacecraft
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Overview
The document discusses a technical report on the synchronization of attitudes and maneuvers of multiple spacecraft flying in formation, specifically focusing on the challenges of rotating the entire formation about a given axis while ensuring that individual spacecraft synchronize their rotations accordingly. This capability is crucial for missions involving long-baseline interferometry, where multiple spacecraft act as platforms for collecting data.
The report outlines the development of control laws necessary for achieving this synchronization, starting from a particle model of spacecraft dynamics and a rigid-body model of spacecraft attitude dynamics. It assumes one spacecraft serves as a reference for the positions and orientations of the others. The authors derive mathematical control laws that can be implemented in the absence of gravitational influences and external disturbances. They also present simplified control laws that are practical for real-world applications.
The work was conducted by Fred Y. Hadaegh and Kenneth Lau from the California Institute of Technology, along with Paul K. Wang from the University of California, under the auspices of NASA’s Jet Propulsion Laboratory. The report emphasizes the novelty of the research, noting that the problem of deriving implementable control laws for formation rotation and attitude synchronization had not been previously addressed.
The document details the motivation behind the research, which stems from the operational requirements of deep-space interferometers that necessitate precise control over the formation's rotation and the individual spacecraft's attitudes. The authors employed Lyapunov’s Direct Method to derive nonlinear control laws for formation rotation and attitude synchronization, providing a priori estimates for tracking error norms. The analytical results were validated through computer simulations using typical spacecraft models, demonstrating the effectiveness of the proposed control laws.
In summary, this report presents a significant advancement in the field of spacecraft formation flying, offering practical solutions for synchronizing the maneuvers of multiple spacecraft. The findings have implications for future deep-space missions that rely on coordinated operations of multiple spacecraft, enhancing the capabilities of space exploration and scientific observation.
