Presentation + Paper
13 December 2020 Performance and limitations of using ELT and MCAO for 50 μas astrometry
Author Affiliations +
Abstract
MCAO is essential to perform astrometry with the Extremely Large Telescope (ELT). Differently from the 8m class telescopes, the ELT will be a fully adaptive telescope, and a significant portion of the Adaptive Optics (AO) dynamic range will be absorbed by the correction and stabilization of the telescope aberrations and instabilities. Of particular interest for the ground-based astrometry is the use of Multi-Conjugated AO systems that allow to stabilize the low order field distortions against the transient plate scale instabilities of different origin occurring at the telescope and in the instrument. The instruments have several optical elements relatively far away from the pupil that can potentially challenge the astrometric precision of the observations with their residual mid-spatial frequencies errors. Using a combined simulation of ray tracing and AO numerical codes we assess the impact of these systematic errors at different field of view scales and fitting scenarios. The distortions have been assessed at different sky Position Angles (PA) and indicate that over large field of views only small PA ranges (±1°-3°) are accessible with astrometric residuals 50 µas. A full compliance, at any PA is achievable for 2 arcsec2 FoV patches already with a 3rd order polynomial. The natural partition of the optical system in three segments, ELT-MAORY-MICADO, respectively telescope, MCAO module and instrument, resembles also a splitting of the astrometric problem in the three subsystems that are characterized by different distortion amplitudes and calibration strategies. The result is a family portrait of the different optical segments with their prescription, dynamic motions, conjugation height and AO correctability, leading to trace their role in the bigger puzzle of the 50 μas astrometric endeavor.
Conference Presentation
© (2020) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
G. Rodeghiero, C. Arcidiacono, Jörg-Uwe Pott, S. Perera, G. Pariani, D. Magrin, H. Riechert, M. Glück, E. Gendron, D. Massari, J. Sauter, M. Fabricius, M. Häberle, S. Meßlinger, R. Davies, P. Ciliegi, M. Lombini, and L. Schreiber "Performance and limitations of using ELT and MCAO for 50 μas astrometry", Proc. SPIE 11447, Ground-based and Airborne Instrumentation for Astronomy VIII, 114471Z (13 December 2020); https://doi.org/10.1117/12.2560373
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KEYWORDS
Adaptive optics

Cameras

Distortion

Deformable mirrors

Device simulation

Geometrical optics

Imaging systems

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