Design and evaluation of an active secondary mirror positioning system for a small telescope

Sinn, Andreas; Prager, Patrik; Schwaer, Christian; Schitter, Georg

doi:10.1117/1.jatis.8.2.029007

Cited by 3 publications

(1 citation statement)

References 27 publications

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“…Therefore, a Strehl ration of 0.85 is awarded to the primary mirror, which equates to an allowed RMS wavefront error of 34 nm. A further main contributor to wavefront aberration is the secondary mirror, which is planned to be active and positioned relative to the primary by means of optical metrology 22 …”

Section: Error Budgetingmentioning

confidence: 99%

Active lateral support system for a thin 1-meter meniscus mirror with virtual fixed points

Schwaer,

Sinn,

Schroeer

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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.This publication presents an active lateral support system for the thin 1-m meniscus mirror of a Ritchey-Chrétien telescope system. The goal is to keep the mirror at its position under varying external influences, such as gravity and temperature, therefore maintaining the alignment and optical image quality. To achieve this, the lateral support consists of eight actuators, based on stepper motors with gearboxes, with local force measurement and three laser triangulation sensors to measure the mirror’s lateral position. A cascaded control structure with local force feedback in the inner loop and position feedback in the outer loop is proposed. In the outer loop, three single-input single-output PI-controllers are implemented to maintain mirror position in the three lateral degrees of freedom. The developed system is able to position the mirror with root mean square errors of 0.27 and 0.18 μm in translational directions and 5.1 μrad in the rotational direction over the operational altitude range with a slewing speed of 0.2 deg / s.

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Section: Error Budgetingmentioning

confidence: 99%

Active lateral support system for a thin 1-meter meniscus mirror with virtual fixed points

Schwaer,

Sinn,

Schroeer

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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Investigation of the parameters of a power truss for fixing mirrors in a telescopic complex for an ultra-low-orbit spacecraft

Peresypkin,

Volotsuev,

Taneeva

2024

E3S Web Conf.

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The design parameters of a power structure for fixing mirrors in the optical circuit of surveillance equipment intended for installation on an ultra-low-orbit spacecraft are being investigated. The optical scheme contains the main and second mirrors, as well as an additional flat mirror with an inclination of forty-five degrees to the optical axis of the main mirror. This flat mirror reverses the direction of the optical rays reflected from the earth's surface and directs the rays at the main mirror. To reduce the weight of the power structure, taking into account the requirements for dimensional stability and vibration resistance, a power truss with conical and unclosed cylindrical sections is considered. As a result of the research, the mass and size parameters of the power truss were obtained, which can serve as the basis for further development of a promising ultra-low-orbit optical system.

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Characterization of an active secondary mirror positioning system for a small telescope

Sinn,

Kreuzmair,

Schwaer

et al. 2024

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI

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This publication presents the characterization of a modular, active secondary mirror positioning system for a small commercial off-the-shelf Ritchey-Chrétien telescope. Relative displacements between primary and secondary mirror are measured using absolute dimensional metrology, requiring no light from the scientific application. Feedback control is implemented to compensate the measured deviations in three degrees of freedom, by means of a custom-made active mount for the secondary mirror. Tip, tilt, and piston of the secondary are controlled to their calculated ideal position with a closed-loop bandwidth of 2 Hz. The proposed system is characterized under asymmetric thermal influences, which include the small impact of gravitational disturbances, using a Shack-Hartmann wavefront sensor and an artificial star. The conducted experiments successfully demonstrate the applicability of the implemented active compensation approach, decreasing the RMS wavefront error by a factor of more than 7, effectively reducing the introduced optical aberrations.

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Design and evaluation of an active secondary mirror positioning system for a small telescope

Cited by 3 publications

References 27 publications

Active lateral support system for a thin 1-meter meniscus mirror with virtual fixed points

Active lateral support system for a thin 1-meter meniscus mirror with virtual fixed points

Investigation of the parameters of a power truss for fixing mirrors in a telescopic complex for an ultra-low-orbit spacecraft

Characterization of an active secondary mirror positioning system for a small telescope

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