4MOST metrology system lab calibration and performance

Roland Winkler; Thomas Liebner; Deborah Sobiella; Carlos Rodriguez Alvarez; Thomas Fechner; Wilbert Bittner; Dietrich Feuerstein; Bjorn Leseberg; Thomas Hahn; Lea Rektorschrek; Ulrike Lemke; Daniel Sablowski; Alexander Pramskiy; Florian Rothmaier; Ingo Stilz; Michael Lehmitz; Scott Smedley; Hakan Onel; Steffen Frey

doi:10.1117/12.2630358

29 August 2022 4MOST metrology system lab calibration and performance

Roland Winkler, Thomas Liebner, Deborah Sobiella, Carlos Rodriguez Alvarez, Thomas Fechner, Wilbert Bittner, Dietrich Feuerstein, Bjorn Leseberg, Thomas Hahn, Lea Rektorschrek, Ulrike Lemke, Daniel Sablowski, Alexander Pramskiy, Florian Rothmaier, Ingo Stilz, Michael Lehmitz, Scott Smedley, Hakan Onel, Steffen Frey

Author Affiliations +

Proceedings Volume 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V; 121882A (2022) https://doi.org/10.1117/12.2630358
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

The 4-meter Multi-Object Spectroscopic Telescope (4MOST) instrument uses 2436 individually positioned optical fibres to couple the light of targets into its spectrographs. The AESOP fibre positioner is mounted at the Cassegrain focus of the VISTA telescope, which houses the fibres in a hexagon-like structure with a diameter of 535 mm that covers a 2.5 deg diameter field of view on the sky. Fibres are positioned relative to fixed fiducial fibres. The metrology system determines the position of the fibres on the focal surface of the telescope relative to the fiducial fibres. The location of the fibres needs to be measured to better than 3 micron RMS in the focal surface, approximately 0.05 arc seconds on sky. Four imaging cameras are mounted on the VISTA spider vanes that look through the entire optical train, including primary and secondary mirror as well as the wide field corrector (WFC) / atmospheric dispersion compensator (ADC) unit. We recreated the setup for the metrology system in the lab with similar dynamic behavior but different optical design due to the lack of the VISTA telescope. We demonstrate the metrology system measurement accuracy in lab conditions on the full scale test stand. We also show how we measure distortions induced by optical path and the calibration procedure as a precursor for commissioning on the telescope. In particular, we present a method how to measure the surface shape of any optical surface with approx. 10 nm accuracy over its entire optically active surface.

Conference Presentation

Citation Download Citation

Roland Winkler, Thomas Liebner, Deborah Sobiella, Carlos Rodriguez Alvarez, Thomas Fechner, Wilbert Bittner, Dietrich Feuerstein, Bjorn Leseberg, Thomas Hahn, Lea Rektorschrek, Ulrike Lemke, Daniel Sablowski, Alexander Pramskiy, Florian Rothmaier, Ingo Stilz, Michael Lehmitz, Scott Smedley, Hakan Onel, and Steffen Frey "4MOST metrology system lab calibration and performance", Proc. SPIE 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V, 121882A (29 August 2022); https://doi.org/10.1117/12.2630358

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available