Passive magnetic attitude stabilization system of the EduSAT microsatellite

Abstract

Passive magnetic attitude stabilization systems are simple, easy to realize, cheap, and do not require software development and on-board energy consumption. Owing to these features, passive magnetic attitude stabilization systems were selected for the EduSAT (Educational Satellite) microsatellite, a student-built satellite funded by the Italian Space Agency, scheduled to be launched in the last quarter year of 2010. The passive magnetic attitude stabilization system is based on a permanent magnet, which provides a restoring torque to align an oriented axis of the satellite with the Earth's magnetic field direction, and an energy dissipation system, which can consist of a set of permeable rods magnetized by the oscillation of the geomagnetic field along their axis. UNISAT-3 attitude determination results after 1 year from its launch demonstrated the necessity of an accurate design and manufacturing process of soft magnetic strips. Predicting system performance in orbit and evaluating the obtainable accuracy are not trivial: the main problem is knowing the effective magnetization of the permeable rods. The paper deals with sizing, choice of material, manufacturing process, and arrangement of a set of permeable rods on board the EduSAT microsatellite on the basis of previous flight experience

Optimal geometry and materials for nanospacecraft magnetic damping systems

“…This approach is quite involved and computation intensive, therefore, not particularly suited for long-term attitude motion numerical propagation. A simplified model has been proposed in [24] and successfully applied for example in [17,18,29,30]. This model has been recently elaborated further, leading to an analytical solution for the hysteresis curves, given an initial condition [14].…”

“…The Earth's magnetic field model is a 10th-order International Geomagnetic Reference Field [33]. The passive magnetic attitude stabilization consists of a pivoting permanent magnet of magnetic moment m = 0.33 Am 2 and two orthogonal arrays of strips in the plane orthogonal to the permanent magnet, as shown in available Nd-Fe-B magnets, verifying that no resonance conditions occur due to the coupling of attitude and orbital motion, as described in [15][16][17][18]. In the numerical simulations presented in Figs.…”

“…Design procedures for evaluation of permanent magnet dipole, depending on the system parameters, such as satellite inertia, orbital height, and inclination, can be found, for example, in [15][16][17][18].…”

“…Actually, a range of values for the magnetization level reached in satellite damping systems is given in the literature. Depending on the rod geometry, material, and treatment, magnetization levels of the order of 0.1 T, 0.7 T, 0.015 T, 0.14 T, 0.07 T, and 0.15 T are reported in [1,3,14,17,18,19], respectively. This shows that the "optimal" material choice, clearly related to the overall geometry of the system, is ill defined and needs further investigation.…”

Volume magnetization for system-level testing of magnetic materials within small satellites

“…The use of an excitation (magnetizing) & sense (or pickup) coil is an accepted method of hysteresis measurement [21]. Recent empirical testing of hysteresis rods for PMAC systems have been performed by two main groups: Ivanov et al [25] (also [26]) use a small excitation solenoid (only magnetizing one hysteresis rod), while Santoni et al [27] (also [28], [29]) use a larger excitation solenoid capable of magnetizing a large array of rods. We present a method of using the Helmholtz cage itself as the excitation coil, as it is able to supply a uniform magnetizing field in a large volume and in any direction.…”