Abstract
To enable a reliable verification of attitude determination and control systems for nanosatellites, the environment of low Earth orbits with almost disturbance-free rotational dynamics must be simulated. This work describes the design solutions adopted for developing a dynamic nanosatellite attitude simulator testbed at the University of Bologna. The facility integrates several subsystems, including: (i) an air-bearing three degree of freedom platform, with automatic balancing system, (ii) a Helmholtz cage for geomagnetic field simulation, (iii) a Sun simulator, and (iv) a metrology vision system for ground-truth attitude generation. Apart from the commercial off-the-shelf Helmholtz cage, the other subsystems required substantial development efforts. The main purpose of this manuscript is to offer some cost-effective solutions for their in-house development, and to show through experimental verification that adequate performances can be achieved. The proposed approach may thus be preferred to the procurement of turn-key solutions, when required by budget constraints. The main outcome of the commissioning phase of the facility are: a residual disturbance torque affecting the air bearing platform of less than 5 × 10−5 Nm, an attitude determination rms accuracy of the vision system of 10 arcmin, and divergence of the Sun simulator light beam of less than 0.5° in a 35 cm diameter area.
Highlights
The growing interest in the development of highly capable nanosatellites for a wide range of scientific missions [1,2,3,4,5] demands a substantial increase of the traditionally low success rate of this kind of miniaturized platforms, which were originally conceived for educational or technological demonstration purposes
Increasingly more studies are found in the literature addressing verification approaches of mission critical subsystems, such as the power [6], propulsion [7], attitude determination and control (ADCS) [8,9], and guidance, navigation, and control [10,11] ones, considered alone or in combination [12,13,14]
For designing and implementing our testbed, we considered as the target application scenario the one of nanosatellite missions in Low Earth Orbit (LEO) for remote sensing, in-orbit demonstration (IOD), or Earth observation, whose pointing requirements often fall in the range from tens of arcminutes to one degree [31,32,33,34]
Summary
The growing interest in the development of highly capable nanosatellites for a wide range of scientific missions [1,2,3,4,5] demands a substantial increase of the traditionally low success rate of this kind of miniaturized platforms, which were originally conceived for educational or technological demonstration purposes. Being typically budget-driven, the reported implementations, despite being effective, often overlook final performance verification, which is either absent or covering some parts of the facility only [29,30] Within this context, the Microsatellite and Space Microsystems Lab at University of Bologna has recently developed a 3DoF testbed, aimed at nanosatellites ADCS hardware and algorithms verification. Other subsystems include a Helmholtz cage for geomagnetic field simulation, a Sun simulator, and a metrology vision system for ground-truth attitude measurement (see Figure 1) Their development and verification required substantial efforts, aimed at achieving good performances, while meeting a rather low cost-cap (20 kEuro).
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