AO4ELT5 Proceedings

The LBT Adaptive Secondary Thin Shells

Brusa, Guido (Large Binocular Telescope Observatory), Sosa, Richard (Large Binocular Telescope Observatory), Lefebvre, Michael J. (Large Binocular Telescope Observatory), Vogel, J. Conrad (Large Binocular Telescope Observatory), McMahon, Tom J. (Large Binocular Telescope Observatory), Christou, Julian C. (Large Binocular Telescope Observatory)

The most critical component of an adaptive secondary mirror (ASM) is its thin shell; this is the deformable part of the ASM and therefore the component actually providing the adaptive correction. Moreover, because of its intrinsic nature, this component is also the most delicate and difficult to maintain, requiring special attention every time it is handled. LBT has three thin shells, one for each ‘eye’ of the telescope and one spare. These shells were produced and put in operation between 2006 and 2011 and since then have become the ‘heart’ of the LBT adaptive optics system. In this paper we report on the maintenance and repair activities that have been carried out during the operation of the LBT adaptive secondary mirrors during the past 5-6 years. In particular we discuss regular maintenance operations such as optical-side surface re-coating and magnet re-gluing as well as extraordinary maintenance such as the re-coating of the magnet-side surface. In addition to techniques and tools used for these activities we will also discuss the strategies put in place for the handling of our thin shell in order to protect and preserve these unique assets.

DOI: 10.26698/AO4ELT5.0147- Proceeding PDF

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