[Paper Review] Attitude Control of the Asteroid Origins Satellite 1 (AOSAT 1)

Ravi Teja Nallapu, Saumil Shah+2 more|arXiv (Cornell University)|Jan 26, 2017

Astro and Planetary Science3 citations

TL;DR

This paper presents the attitude control system design for AOSAT 1, a 3U CubeSat that uses a reaction wheel and magnetorquers to spin at up to 4 rpm, simulating milligravity conditions on small asteroids. The study analyzes de-tumbling performance and stability under internal mass shifts from crushed meteorites, demonstrating robust control for future low-cost in-orbit centrifuge laboratories in planetary science.

ABSTRACT

Exploration of asteroids and small-bodies can provide valuable insight into the origins of the solar system, into the origins of Earth and the origins of the building blocks of life. However, the low-gravity and unknown surface conditions of asteroids presents a daunting challenge for surface exploration, manipulation and for resource processing. This has resulted in the loss of several landers or shortened missions. Fundamental studies are required to obtain better readings of the material surface properties and physical models of these small bodies. The Asteroid Origins Satellite 1 (AOSAT 1) is a CubeSat centrifuge laboratory that spins at up to 4 rpm to simulate the milligravity conditions of sub 1 km asteroids. Such a laboratory will help to de-risk development and testing of landing and resource processing technology for asteroids. Inside the laboratory are crushed meteorites, the remains of asteroids. The laboratory is equipped with cameras and actuators to perform a series of science experiments to better understand material properties and asteroid surface physics. These results will help to improve our physics models of asteroids. The CubeSat has been designed to be low-cost and contains 3-axis magnetorquers and a single reaction-wheel to induce spin. In our work, we first analyze how the attitude control system will de-tumble the spacecraft after deployment. Further analysis has been conducted to analyze the impact and stability of the attitude control system to shifting mass (crushed meteorites) inside the spacecraft as its spinning in its centrifuge mode. AOSAT 1 will be the first in a series of low-cost CubeSat centrifuges that will be launched setting the stage for a larger, permanent, on-orbit centrifuge laboratory for experiments in planetary science, life sciences and manufacturing.

Motivation & Objective

• To develop a low-cost, reliable attitude control system for AOSAT 1, a CubeSat designed to simulate milligravity conditions on small asteroids.
• To analyze the de-tumbling performance of the spacecraft after orbital deployment using 3-axis magnetorquers and a reaction wheel.
• To evaluate the stability of the attitude control system when internal mass shifts occur due to the movement of crushed meteorites during centrifuge operation.
• To enable future in-orbit centrifuge laboratories for planetary science by de-risking technology for asteroid landing and resource processing.
• To support fundamental studies of asteroid surface physics and material properties through controlled microgravity simulations.

Proposed method

• The attitude control system employs a single reaction wheel for spin-up and 3-axis magnetorquers for de-tumbling and momentum desaturation.
• The system uses a proportional-integral-derivative (PID) control law to regulate the spacecraft's spin rate and maintain attitude stability.
• A dynamic model of the spacecraft accounts for internal mass shifts from crushed meteorites during centrifuge operation.
• Stability analysis is performed using linearized equations of motion to assess system response under varying mass distribution.
• The control architecture includes a detumbling mode that transitions from magnetic torque control to reaction wheel control after deployment.
• Simulations and analytical models are used to evaluate control performance under realistic perturbations and mass shift scenarios.

Experimental results

Research questions

• RQ1 How effective is the magnetorquer-based de-tumbling control system in stabilizing AOSAT 1 after orbital deployment?
• RQ2 What is the impact of internal mass shifts from crushed meteorites on the attitude control system's stability during centrifuge operation?
• RQ3 How does the reaction wheel contribute to maintaining a stable spin rate of up to 4 rpm in the presence of internal disturbances?
• RQ4 What are the dynamic coupling effects between the spinning centrifuge and the spacecraft's overall attitude control system?
• RQ5 Can the combined magnetorquer and reaction wheel system maintain long-term stability under realistic mass shift conditions?

Key findings

• The attitude control system successfully achieves de-tumbling within a few orbits using magnetorquers and reaction wheel control.
• The system maintains stable spin at up to 4 rpm despite internal mass shifts from crushed meteorites, as confirmed by simulation and stability analysis.
• The linearized dynamic model shows that the control system remains stable under varying mass distribution, with no significant loss of control authority.
• The reaction wheel provides sufficient control authority to maintain precise spin rate regulation during centrifuge operations.
• The integration of magnetorquers and a single reaction wheel enables a low-cost, reliable attitude control solution for a spinning CubeSat platform.
• The study confirms the feasibility of using a single reaction wheel for spin control in a low-cost, small-satellite centrifuge laboratory.