CubeSat

Résumé

vignette|ESTCube-1, un CubeSat 1U estonien. CubeSat, appelé également en France nanosatellite cubique, est un format de satellite artificiel qui est le plus couramment utilisé pour les engins de très petite taille (moins de 20 kilogrammes). Son cahier des charges définit sa forme, sa masse maximale ainsi que certaines des caractéristiques de ses composants et de son fonctionnement. Dans sa forme basique, appelée 1U, c'est un cube (d'où son appellation) de de côté et dont la masse ne doit pas excéder deux kilogrammes. La majorité des CubeSats sont formés par la juxtaposition de plusieurs cubes élémentaires (de 2U jusqu'à 24U). Le cahier des charges définissant les caractéristiques des Cubesats est rédigé en 1999 par l'Université polytechnique de Californie et l'université Stanford (États-Unis). L'objectif en est de réduire les coûts de lancement des très petits satellites et ainsi de permettre aux universités de développer et de placer en orbite leurs propres engins spatiaux. Le pro

Source officielle

https://fr.wikipedia.org/wiki/CubeSat

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SwissCube Inertial Wheel Assembly Electronics

Laurenz Notter

The overall goal is the development of a new control software for the inertial wheel assembly of the SwissCube project. SwissCube is an educational project of several Swiss universities and technical colleges under the supervision of the Space Center of EPFL1. The SwissCube is a pico-satellite which respects the CubeSat standard and is almost entirely built by students from the different participating universities. The inertial wheel assembly (IWA) is composed of the IWA motor, the inertial wheel itself and the command electronics. The system fulfills two functions at the same time: • Stabilization of the spatial orientation of the satellite using the gyroscopic effect (used as a momentum wheel) • Controlled rotation of the satellite around the axis of rotation of the IWA for compensation of in-orbit perturbations as well as reorientation (reaction wheel mode)

2010

Chargement

Is it possible to dock CubeSats in Low Earth Orbit? Challenges are associated with the level of miniaturisation: the docking accuracy is driven by the docking mechanism dimensions. The achievable docking performance with the Guidance, Navigation and Control (GNC) subsystem is constrained by the use of small sensors and actuators. A docking mechanism prototype, tailored for CubeSats was designed, built and tested in the laboratory using a simple experimental setup. Results showed that a lateral precision of 1 cm and a relative angular alignment better than 2 degrees are required to guarantee successful docking. A filtered monocular camera on the chaser satellite and various arrays of light-emitting diodes on the target vehicle were selected for the metrology, due to their potential to achieve a high relative navigation accuracy and to ensure the observability of the system throughout the final approach trajectory. Both docking mechanism and metrology system are contained within 0.5U volume and can thus be used on a wide span of satellite types. The chaser and target have a complete 3-axis attitude pointing capability and are equipped with off-the-shelf CubeSats attitude sensors and actuators, including star trackers and reaction wheels. The chaser is further equipped with a six degrees of freedom low-thrust cold gas propulsion system. The navigation and control functions rely on a linearised coupled dynamic, which includes fuel sloshing effects, and describes the 6 degrees of freedom relative motion between the chaser and target docking ports. Using this dynamic, LQR, LQI, H-Infinity and Mu-Synthesis controllers were investigated and their stability and performance assessed by mean of Mu-Analysis. A comprehensive simulation framework was developed to evaluate the performances of the navigation and control functions and the impact of actuator and sensor errors on the overall docking performance. The environmental and internal perturbations, such as atmospheric drag and fuel sloshing were taken into account. All sensors and actuators required for the docking were modelled, including realistic errors and noise characteristics. Different docking scenarios were investigated based on the different behaviour of the coupled dynamics. Worst-case scenarios such as the loss of sensor signals prior to docking are also tackled. The robustness of the proposed control schemes was assessed by the use of structured singular values. Complementary non-linear Monte-Carlo simulations were also performed to determine the complete GNC performances as well as fuel consumption. Results show that the proposed GNC is robust to the modelled sensor and actuator noises, fuel sloshing, dynamics uncertainties and that a lateral position accuracy better than 5 mm can always be obtained at docking. Furthermore, docking is not affected by the loss of star tracker signals nor by harsh illumination conditions, and can thus take place on a variety of orbits.

EPFL2018

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Mission Design and GNC for In-Orbit Demonstration of Active Debris Removal Technologies with CubeSats

Federico Belloni, Volker Gass, Christophe Dominique Paccolat, Camille Sébastien Pirat, Muriel Richard, Reto Wiesendanger

Within the frame of the ESA's General Support Technology Programme, two In-Orbit Demonstration (IOD) missions using CubeSat technologies were studied. These IODs aim at alleviating the technical risk inherent to new technologies required for Active Debris Removal (ADR) of large space objects, by using small and low-cost CubeSat systems. Rendezvous and docking with uncooperative debris has been only partially demonstrated and still raises technological issues. To test technologies such as the navigation and Rendezvous (RV) sensors or capture systems, our studies show that CubeSat missions are appropriate. Already, Guidance, Navigation and Control (GNC), communications and power technologies have successfully been miniaturised and the corresponding equipments are now available to the CubeSat community. This fact extends the range of feasible CubeSat missions from the initial flight of simple sensors to more complex systems. This paper presents two CubeSat ADR experiments and demonstrates how mission design and GNC can serve the verification or navigation sensors performances as well as the validation of uncooperative debris capture using a net. Each mission is composed of a Chaser and a Target. The former being an 8 Units (8U) CubeSat and the latter a 4U, launched together in a 12U deployer. Both satellites are 3-axis attitude controlled. The Chaser has in addition 3 Degrees of Freedom (DoF) translation capability using 1 mN cold gas thrusters. Both CubeSats will carry GNSS receivers to assist in the determination of range and relative-velocity. The global positioning and attitude data or the Target will be transmitted to the Chaser using an inter-satellite link having the additional capacity to measure the corresponding range. This system provides a reference validation for the RV sensors. The relative position and velocity to be controlled are fully observable. Thus a linear quadratic regulator is appropriate to ensure robust and optimal control. Based on the mission design, various close inspection configurations are demonstrated. To emphasise the feasibility of such missions, a system approach will be briefly addressed. Both missions are analysed using a 6 DoF simulator. The performances and absolute errors of the GNC as well as fuel consumption are provided. Power consumption, Telecom capability and thermal aspects will be shown for sake of completeness. Current issues and limitations of the CubeSat GNC will be discussed, as well as conclusions regarding the feasibility of such missions.

Elsevier2016

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Mission Design and GNC for In-Orbit Demonstration of Active Debris Removal Technologies with CubeSats

Federico Belloni, Volker Gass, Christophe Dominique Paccolat, Camille Sébastien Pirat, Muriel Richard, Reto Wiesendanger

Elsevier2016

EPFL2018