Session
Technical Session 3: Year in Review
Location
Utah State University, Logan, UT
Abstract
This research presents the results of an in-orbit test of the orbital altitude control for a micro-satellite equipped with the first space-demonstrated high-density small cold gas jet thruster. In the field of micro-satellites, the application of thrusters to practical missions has not yet progressed due to their high cost, mechanical and electrical incompatibility with the satellite bus system, and increased operational risks. By contrast, the demand for orbit control functions has been increasing in recent years with the expansion of micro-satellite applications. The76kg satellite "ALE-2", which was jointly developed by Tohoku University and ALE Co., Ltd., has the world's first challenging mission to artificially generate shooting stars by ejecting small substances (meteor source) from the ejection device fixed on the satellite body. To avoid collision of the ejected meteor source with other flying objects, the mission must be performed in a sun-synchronous orbit at an altitude of less than 400 km, which is lower than that of the International Space Station. However, it is required to maintain the mission orbit autonomously because the orbit decay is large due to the effect of atmospheric drag. In addition, to release the meteor source at an arbitrary orbital position, it is essential to manipulate the ground track by raising and lowering the orbital altitude. Therefore, ALE-2 needs to control the orbit altitude actively and with arbitrary amount of change. In this study, the reaction control system (RCS), which satisfies the orbit change capability, mission requirements, and compatibility with the satellite bus system, is installed on ALE-2 to perform space demonstrations of orbit control and to evaluate the operational performance of the thruster. ALE-2 will be the first to be equipped with a cold gas jet thruster developed by Patched conics, LLC. It is estimated that the thruster is capable of changing altitude more than 1 km by continuous drive for one orbital period. Using this RCS, the following three criteria were set as the evaluation criteria: (Minimum) the orbit altitude can be actively changed by the thruster, (Full) the orbit altitude can be controlled by an arbitrary amount of operation and can be increased more than 1 km per orbit, and (Extra) the mission orbit can be transferred according to the meteor source release plan. ALE-2 was launched on December 6, 2019, and the in-orbit test of the RCS started four months later. Although the RCS was not able to achieve its initial orbit change capability due to an anomaly in the power supply system, various kinds of tests were conducted under conditions that allowed continuous thruster operation. It was confirmed that the orbit altitude was increased by 0.4 km per orbit. In addition, the fault detection, isolation and recovery (FDIR)function was effectively performed against any kinds of anomalies of RCS during in-orbit operation. Therefore, a sustained orbital altitude of 400 km was expected to be achievable using the onboard RCS.
In-orbit Demonstration of Reaction Control System for Orbital Altitude Change of Micro-Satellite ALE-2
Utah State University, Logan, UT
This research presents the results of an in-orbit test of the orbital altitude control for a micro-satellite equipped with the first space-demonstrated high-density small cold gas jet thruster. In the field of micro-satellites, the application of thrusters to practical missions has not yet progressed due to their high cost, mechanical and electrical incompatibility with the satellite bus system, and increased operational risks. By contrast, the demand for orbit control functions has been increasing in recent years with the expansion of micro-satellite applications. The76kg satellite "ALE-2", which was jointly developed by Tohoku University and ALE Co., Ltd., has the world's first challenging mission to artificially generate shooting stars by ejecting small substances (meteor source) from the ejection device fixed on the satellite body. To avoid collision of the ejected meteor source with other flying objects, the mission must be performed in a sun-synchronous orbit at an altitude of less than 400 km, which is lower than that of the International Space Station. However, it is required to maintain the mission orbit autonomously because the orbit decay is large due to the effect of atmospheric drag. In addition, to release the meteor source at an arbitrary orbital position, it is essential to manipulate the ground track by raising and lowering the orbital altitude. Therefore, ALE-2 needs to control the orbit altitude actively and with arbitrary amount of change. In this study, the reaction control system (RCS), which satisfies the orbit change capability, mission requirements, and compatibility with the satellite bus system, is installed on ALE-2 to perform space demonstrations of orbit control and to evaluate the operational performance of the thruster. ALE-2 will be the first to be equipped with a cold gas jet thruster developed by Patched conics, LLC. It is estimated that the thruster is capable of changing altitude more than 1 km by continuous drive for one orbital period. Using this RCS, the following three criteria were set as the evaluation criteria: (Minimum) the orbit altitude can be actively changed by the thruster, (Full) the orbit altitude can be controlled by an arbitrary amount of operation and can be increased more than 1 km per orbit, and (Extra) the mission orbit can be transferred according to the meteor source release plan. ALE-2 was launched on December 6, 2019, and the in-orbit test of the RCS started four months later. Although the RCS was not able to achieve its initial orbit change capability due to an anomaly in the power supply system, various kinds of tests were conducted under conditions that allowed continuous thruster operation. It was confirmed that the orbit altitude was increased by 0.4 km per orbit. In addition, the fault detection, isolation and recovery (FDIR)function was effectively performed against any kinds of anomalies of RCS during in-orbit operation. Therefore, a sustained orbital altitude of 400 km was expected to be achievable using the onboard RCS.
