![]() This article outlines the development and feasibility of novel autonomous WOL strategies. Such procedure is known as desaturation or Wheel Off-Loading (WOL). If this occurs, the angular momentum must be removed from the wheel, reducing its speed while providing an opposite torque on the Spacecraft (S/C) to avoid drifts of the attitude. These actuators are highly reactive and precise however, when one wheel reaches the maximum angular rate, it is said to be saturated and can not produce torques anymore. ![]() Īll of these platforms use Reaction Wheels (RWs) to reject the attitude disturbances and control the orientation. Following the success of MarCO, several deep-space CubeSats missions have been scheduled, such as NEA Scout, Lunar IceCube, Lumio, Juventas & Milani and M-Argo. Now they are planned to be used by national space agencies also for interplanetary missions, with a high scientific return. When they were first designed, CubeSats were addressed to Low Earth Orbits (LEO) missions, mainly for educational purposes. ![]() In the last years, the space sector has been characterized by a strong push in the nano-satellite class, enabling possibilities of exploration and technological demonstrations at relatively low costs. Sensitivity analyses are also carried out on the initial angular momentum components and the center of mass displacement to check the robustness of the algorithms. During the coasting arcs, the solar arrays are tilted and several hours are required, depending on the Sun direction and intensity, but the propellant is completely saved. The trajectory is shown to have negligible differences with respect to the nominal one, since the thrust is corrected accordingly. The off-loading during the cruising arcs employs the gimballed thruster and takes typically 3 h, granting a mass savings of more than 99% with respect to the usage of a reaction control system. The strategies decision-making is autonomously carried out by a state machine. The M-Argo CubeSat is selected as case study to test the techniques along its deep-space trajectory. The dumping on the third axis can be still accomplished by imposing a specific attitude trajectory with the motion of either the gimbal or the arrays drive mechanism. The momentum accumulated along two body axes can be removed by either offsetting the main thruster with a gimbal mechanism or by tilting differentially the solar wings. This work elaborates the possibility of off-loading the reaction wheels without the need of carrying a bulky and expensive reaction control system or the field-dependent magnetotorquers. Deep-space CubeSats missions require careful trade-offs on design drivers such as mass, volume, and cost, while ensuring autonomous operations. ![]()
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