Invited - Adaptive Secondary Mirror Development at TNO

TNO High Tech Industry, 2264CK, Delft, The Netherlands.

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Published online: 22 September 2025

Abstract

Adaptive Optics (AO) is a key technology to enhance the imaging performance of ground based astronomical telescopes, compensating the atmospheric aberrations through an adaptive mirror. To enhance the efficiency of these AO systems, many observatories aim to integrate the adaptive mirror within the secondary mirror of the telescope, resulting in an adaptive secondary mirror (ASM). TNO is developing ASM’s based on a unique and highly efficient electromagnetic actuator technology, which high force output enable the use of relatively thick mirror shells (>3,5mm) and no need for active cooling through their high energy efficiency. These aspects lead to an overall highly robust and reliable ASM system, which is considered a key requirements for such active components that are built into the heart of the telescope. TNO has realized two prototypes ASM systems for the NASA IRTF telescope (~24cm,and 36 actuators, readily installed and tested) and the UH-88 telescope (~62cm and 204 actuators, currently going through factory acceptance testing). Building on to these prototype results is the development of mature ASM systems aimed to serve the world largest ground based observatories, including the ASM for the KECK telescope (~1.4m and ~3400 actuators).