Transferring an Earth-based Adaptive Optics Technology to Space Telescopes

Lorenzo Dozio, Paolo Mantegazza, Marco Bevilacqua


The present work is aimed at studying the application of a contactless
voice-coil actuation technology, currently developed for some new-generation
earth telescopes, to an hypothetical secondary mirror of a space telescope
subjected to nanometric precision requirements.
The technology involves a large number of electromagnetic actuators
which are not in contact with the optical mirror.
Each actuator is made by a fixed coil wound on a cold finger and a moving magnet,
glued to the rear surface of the thin adaptive mirror.
A stiff backplate provides the position reference.
The gap between the mirror and the backplate is measured
through co-located capacitive sensors.
Since future space telescopes will operate at cryogenics temperatures,
where the material damping is extremely small, the design of high-performance
and stable active shape controllers without detrimental spillover effects is challenging.
Due to the impossibility to exploit aerodynamic damping arising
from the squeezed air film between the mirror and the backplate,
as done on earth-based mirrors, there is the need of finding an alternative
to damp out vibrations.
For this purpose, the current-driven technology implemented in earth-based
applications is replaced by a voltage-driven solution, which provides damping
augmentation by means of eddy currents.
This is crucial in achieving a sufficiently stable dynamic response.
The related limitation in the control bandwidth is fully compatible
with the promptness requirements of the control system for the application under study.


Large aperture space telescopes; Contactless voice-coil actuation; Voltage-driven voice coils; Shape control; Damping augmentation; Optimal output feedback control

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M. Laslandes, C. Hourtoule, E. Hugot, et al., "Space active optics: performance of a deformable mirror for in-situ wave-front correction in space telescopes", Proc. SPIE, 8442, 2012.

M. Manetti, M. Morandini and P. Mantegazza, "Control System Design of Active Primary Mirror for the Advanced LIDAR Concept Satellite", Internal Report, Politecnico di Milano, Milano, 2007.

D.C. Redding, G. Hickey, G. Agnes, et al., "Active Optics for a 16-Meter Advanced Technology Large Aperture Space Telescope", Jet Propulsion Laboratory, Caltech, CA, 2008.

M. Laslandes, E. Hugot, M. Ferrari, et al., "Mirror actively deformed and regulated for applications in space: design and performance", Optical Engineering, Vol. 52, No. 9, 2013.

A. Zuccaro Marchi, P. Hallibert, J. Pereira do Carmo, and E. Wille, "Active optics for space applications: an ESA perspective", Proc. SPIE, 9151, 2014.

J.P. Gardner, J.C. Mather, M. Clampin, et al., "The James Webb Space Telescope", Space Science Reviews, Vol. 123, No. 4, 2006.

P.Y. Madec, "Overview of deformable mirror technologies for adaptive optics and astronomy", Proc. SPIE, 8447, 2012.

R. Biasi, D. Gallieni, P. Salinari, et al., "Contactless thin adaptive mirror technology: past, present, and future", Proc. SPIE, 7736, 2010.

"Announcement of Opportunity: Active Optics correction chain for large monolithic mirrors", European Space Agency, 2014.

M. Manetti, "High precision shape control of massively actuated, magnetically levitated, secondary adaptive mirrors for extremely large telescopes", PhD Thesis, Politecnico di Milano, 2010.

M. Manetti, M. Morandini and P. Mantegazza, "High precision massive shape control of magnetically levitated adaptive mirrors", Control Engineering Practice, Vol. 18, No. 12, pp. 1386-1398, 2010.

M. Manetti, M. Morandini and P. Mantegazza, "Self-Tuning Shape Control of Massively Actuated Adaptive Mirrors", IEEE Transactions on Control Systems Technology, Vol. 22, No. 3, pp. 838-852, 2014.

M. Manetti, M. Morandini, P. Mantegazza, et al., "Modeling and control of massively actuated, magnetically levitated, adaptive mirrors", IEEE International Conference on Control Applications, pp. 860-866, 2010.

M. Manetti, M. Morandini, P. Mantegazza, et al., "Experimental validation of massively actuated deformable adaptive mirror numerical models", Control Engineering Practice, Vol. 20, No. 8, pp. 783-791, 2012.

SCHOTT, glass made of ideas,

M.B. Levine and C. White, "Material damping experiments at cryogenic temperatures", Optical Science and Technology, SPIE's 48th Annual Meeting, pp. 165-176, 2003.

C.-Y. Peng, M.B. Levine, L. Shido, and R.S. Leland, "Experimental observations on material damping at cryogenic temperatures", Optical Science and Technology, the SPIE 49th Annual Meeting, pp. 44-62, 2004.

C.-Y. Peng, M.B. Levine, L. Shido, et al., "Measurement of vibrational damping at cryogenic temperatures for silicon carbide foam and silicon foam materials", Proc. SPIE, 5868, 2005.

A.C. Carrier, B. Romney and R. Mihara, "Damping characteristics of composite petal structure for an 8-m diameter telescope at cryogenic temperature", Proc. SPIE, 5487, 2004.

M. Bevilacqua, "Transferring an Earth Based Adaptive Optics Technology to Space", Master Thesis, Politecnico di Milano, 2015.

H. Kwakernaak and R. Sivan, Linear optimal control systems, Wiley, 1972.

C.C. Lin, K.H. Lu and L.L. Chung, "Optimal discrete-time structural control using direct output feedback", Engineering Structures, Vol. 18, No. 6, pp. 472-480, 1996.

R. Isermann, Digital control systems - Volume 2 : Stochastic control, multivariable control, adaptive control, applications, 2nd edition, Springer-Verlag, Berlin, 1991.

R. Skelton, K.M. Grigoriadis and T. Iwasaki, A unified algebraic approach to linear control design, Taylor and Francis, London, 1998.

J.D. Johnston, J.M. Howard, G.E. Mosier, et al., "Integrated modeling activities for the James Webb Space Telescope: structural-thermal-optical analysis", Proc. SPIE, 5487, 2004.



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