Analysis of the system dynamics of small deployable telescopes and the impact of support structures

This paper presents a systematic analysis of the system dynamics of small telescope systems with an aperture below 0.5 m and total weight below 150 kg for deployable operation on support structures with limited mass and stiffness. Structural modes, introduced by either foundation or subcomponents, typically limit the achievable bandwidth of telescope systems to the single Hertz range. Identifying performance-limiting factors is crucial for further improving the pointing and tracking performance. This knowledge allows the optimization of the system for high closed-loop bandwidths and, therefore, enables applications with a demand for high dynamics and fast motion, such as uncrewed aerial vehicle (UAV) tracking. In this work, the dynamics of support structures, the telescope mount, and subcomponents are investigated in the frequency domain by a combination of finite element method (FEM) simulations and in situ measurements from motor encoders and accelerometers. A mean absolute percentage error of 20 % is achieved between FEM simulations and measurements. Laboratory results are further validated by outdoor experiments, indicating the transferability of dynamic characteristics to deployable field operation. The analysis demonstrates that compliant coupling between support structures and ground mainly influences the system dynamics in the low-frequency range. Passive damping measures are investigated for the improvement of the system dynamics, with the first resonance of the altitude axis observed at 7 Hz without damping and 20 Hz with damping. Additional investigations cover the impact of different foundations, damping strategies, ground fixation, inertia variation, and load dynamics. Based on identifying resonance modes and weak spots, recommendations for structural enhancement are provided. These findings support the design of deployable telescope systems with improved dynamic performance and higher closed-loop bandwidths, enabling their use in demanding applications that require fast and precise tracking. • Systematic evaluation of the system dynamics of a small deployable telescope system for operation on lightweight structures with limited stiffness, damping, and mass properties. • Demonstration of the drastic impact of supportive structures on system dynamics, especially in the low frequency range, and the beneficial impact of introducing measures to improve damping. • Identification of mode shapes and mechanical weak spots by a combination of FEM simulations and experimental measurements, providing valuable insight for structural enhancements to extend the system bandwidth.