1 / 24

Properties of the Focal Stations of the Euro50 Mette Owner-Petersen, mette@astro.lu.se

Properties of the Focal Stations of the Euro50 Mette Owner-Petersen, mette@astro.lu.se Lund Observatory, Sweden. Instrumentation for Extremely Large Telescopes Ringberg Castle, Bavaria, 25-29 July 2005. I. Contents. Basic optical layout of the Euro50 Prime focus corrector

roxy
Télécharger la présentation

Properties of the Focal Stations of the Euro50 Mette Owner-Petersen, mette@astro.lu.se

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Properties of the Focal Stations of the Euro50 Mette Owner-Petersen,mette@astro.lu.se Lund Observatory, Sweden Instrumentation for Extremely Large Telescopes Ringberg Castle, Bavaria, 25-29 July 2005 I

  2. Contents • Basic optical layout of the Euro50 • Prime focus corrector • A brief reminder of AO properties & limitations • Focal stations of the Euro50 • The atmospheric dispersion compensator (ADC) • Optical properties of the corrected prime focus (seeing limited) • Optical properties of Nasmyth focus 1 (seeing limited) • Optical properties of Gregorian focus 1 (SCAO, GLAO) • Optical properties of Gregorian focus 2 (DCAO) • Optical properties of Nasmyth focus 2 (DCAO) • Mechanical properties of the focal stations

  3. 1 3 8 6 2 4 7 5 Basic Optical Layout of the Euro50 1 Segmented primary 2 Deformable secondary (DM1) 3 Beamsplitter 4 Intermediate focus (Gregorian focus 1) 5 Collimating mirror 6 Flat deformable mirror (DM2) 7 Focusing mirror 8 Final focus (Gregorian focus 2)

  4. 2 2 1 3 4 Prime Focus Corrector (Seeing Limited Mode) 1 Prime focus 2 Clamshell corrector 3 Achromatic doublet 4 Corrected focus NB: The corrector can be positioned and the corrected focus can be accessed without removing the secondary (DM1)

  5. AO Properties and Limitations A Brief Reminder • PSF properties • Peak Intensity (Strehl Ratio) • Resolution (FWHM) • Contrast (Background Level) PSF profile Observational Importance Strehl Ratio:Detection of faint objects FWHM:Resolving bright objects in crowded fields Contrast:Direct Exo-Planet observation

  6. Model of the Partially Corrected Long Exposure PSF General Valid for ELTs SR = exp( - 2Res ) (Strehl Ratio) Residual wavefront variance: 2Res Residual tip/tilt: αRes (FWHM) Power spectrum of residual fluctuations: Wres (Contrast)

  7. Primary Error Sources • Atmosphere • Telescope Vibrations under Wind Load Dominates for the Euro50 • Thermal Effects

  8. Secondary Error Sources Result: Only partial correction • Fitting Error (Limited spatial resolution of DM) • Aliasing Error (Discrete wavefront sampling) • Servolag Error (Delayed control of DM) • Detection Error (Measurement noise) • Anisoplanatic Error (Correction and measurement at different stellar angles) • Chromatic Error (Correction and measurement at different wavelengths)

  9. Different AO Modes • Single Conjugate Adaptive Optics (SCAO). Both NGS and LGS. One DM and one guide star -> High Strehl but small corrected field. • Ground Layer Adaptive Optics (GLAO). NGS. The easy game. One DM and several guide stars -> Low Strehl but narrow FWHM over a large field. • Multi Conjugate Adaptive Optics (MCAO). Both NGS and LGS. Several DMs and several guide stars -> High Strehl and large corrected field. • Extreme Adaptive Optics (ExAO). NGS. The hard bargain One DM and one Guide Star. Complicated filtering in both image and pupil plane -> Extremely high contrast.

  10. SCAO versus MCAO

  11. Euro50 Overview

  12. Offner-like relay Nasmyth focus 1 Seeing limited ADC Nasmyth focus 2 DCAO Gregorian focus 1 SCAO, GLAO Gregorian focus 2 DCAO LGS Wavefront sensor Focal Stations of the Euro50

  13. The ADC (Preliminary Design) 1 Red ray 2 Blue ray 3 Intermediate cross-point 4 Telescope focal plane 5 Telescope pupil 6 Optical axis hd: Linear dispersion hs: Focus shift

  14. Linear Dispersion at the ORM Site. Z = 45o R: Linear dispersion dA: Diffraction diameter Conclusion: The ADC may not be needed for K-band operation of the Euro 50

  15. Corrected Prime Focus (Seeing Limited) Optical Properties

  16. Nasmyth Focus 1 (Seeing Limited) Optical Properties

  17. Gregorian Focus 1 (SCAO, GLAO) Optical Properties

  18. 60” Strehl color scale Gregorian Focus 1 (Strehl Maps @ 2.2m) SCAO GLAO: 5 Guide Stars in a Cross Infinite outer scale Infinite outer scale 20 m outer scale 20 m outer scale

  19. 4’ 1’ 10’ Infinite outer scale 1’ 10’ 4’ d 20 m outer scale Gregorian Focus 1 (GLAO PSFs @ 2.2m) Guide star configuration

  20. Gregorian Focus2 @ Nasmyth Focus 2 DCAO @ 2.2m Optical Properties Gregorian 2 Nasmyth 2

  21. Gregorian Focus 2 @ Nasmyth Focus 2 (Strehl Maps @ 2.2m) Guide star configuration Infinite outer scale 20 m outer scale

  22. Mechanical Properties Instrument volume Red arrow: Optical axis Black dot: Axial focus *Secondary not removed **Relative to Nasmyth platform ***Sep. of two opt. Axes: 2.29 m

  23. !! Warning !! Estimates of performance are overly optimistic • Wind effects are not accounted for. Must await results from integrated modeling. Will dominate over atmospheric effects. • Only the fitting error and the anisoplanatic error is accounted for. End

More Related