The two faces of the METIS Adaptive Optics system

1. The two faces of the METIS Adaptive Optics system Remko Stuik, Stefan Hippler, Andrea Stolte, Bernhard Brandl, Lars Venema, Miska Le Louarn, Matt Kenworthy, Rainer Lenzen, Eric Pantin, Joris Blommaert, Alistair Glasse, Michael Meyer, and the METIS consortium

2. Outline The science & METIS AO System The SCAO system The LTAO system Conclusions

3. Summary • METIS • mid-IR imager & Spectrograph • 3rd on ESO Roadmap: ELT-MIR • Phase A: • Internal SCAO • External LTAO(ATLAS  ?) • Strong consortium • Refining science &requirements • Preparing kick-off • Definition Interfaces • Includes LTAO

4. Instrument Baseline 1. An imager at L/M & N band with an 18˝×18˝ wide FOV. The imager includes: • Coronagraphy at L/M and N-band • Long slit, low-resolution (R ~ 5000) spectroscopy at L/M & N • Polarimetry at N-band [TBC]. 2. An IFU fed, high resolution spectrograph at L/M band • [2.9 – 5.3μm] with a FoV of ≈0.4˝×1.5˝ and • a spectral resolution of R≈100,000. All subsystems work at the diffraction limit • METIS requires AO correction

5. Science versus AO Requirements The Science • Discovery and Characterization of Exoplanets. • CircumstellarDisk Structure and Evolution • Formation and Evolution of Stars and Star Clusters. • Physics and Chemistry of the Solar System. • Formation and Evolution of Galaxies. • Unique Scientific Opportunities. The AO System • High Contrast/Low residual jitter • Correction over a larger field of view • Embedded sources • Tracking on moving sources • High sky coverage/Extended sources • Flexible AO system

6. The two faces SCAO • Excellent on-axis • Integrated in METIS • Minimize residual jitter • ‘simple’ first light AO BUT: • Requires bright GS • Low sky coverage • No performance in field • Strong drop towards edge LTAO • Wide(r) field performance • Accepts fainter GS(s) • Increased sky coverage BUT: • Decreased on-axis • Separate system • Larger jitter • Increased complexity Note: Both systems required to reach full potential of METIS

7. SCAO Implementation • SCAO internal to METIS • Cold, low (M)IR background • Dichroic first optic inside METIS • Cold! • Splits at ~2.5 micron • Full METIS field ~18x18” • Large field selector • Full METIS field • Allows or field de-rotation • ~40x40 sub-apertures • Reduced complexity • IR WFS • Embedded sources • Selex experience Gravity • Pyramid WFS • Detector available • But extended sources? Dichroic ELT Focus METIS Entrance Window Field Selector ADC? Pupil de-rotator

8. SCAO Simulations • Currently running YAO simulations • Specific science cases • Include spiders, segmentation,… • Investigate static speckles • But currently limited to AO impact only • Provide input METIS science team • Next slide • To do: WFE/vibrations • telescope + instrument • Stefan Hippler, Matt Kenworthy & RS

9. Massive YAO Simulation for the METIS INM • 2 Seeing Conditions (0.6 & 0.8”) • 4 Zenith angles (0, 30, 45, 60°) • 4 Off-axis angles (0, 10, 20, 30°) (18x18”) • 9 Star brightnesses (K=7..15) • 4 Wavelengths (2.0(WFS), 3.5, 4.7, 10.0 µm) • 37 meter, 11.1 central obscuration • Spiders + segmentation included • 40x40 subapertures, Shack-Hartmann WFS, K-band only(!) • ~Paranal atmosphere, Outer scale 25 m, K=13 Sky Background • 1 sec integration @ 1000 Hz, 3e- RON, 0.56 throughput to WWFS

10. SCAO Sky Coverage Forget getting any sky coverage on random targets

11. LTAO I • Phase A: • Facility LTAO: ATLAS • Next phase: • Pre-focal station? • Directly attached to METIS? • Piggybacking on Harmony LTAO • Relaxed specs  own solution? • Several free parameters • LGS locations • Trade-off performance, clear LGS path & clear science path • NGS off-axis distance • Inside METIS (re-use SCAO)? • External WFS? • NGS Tomography? • NGS order • Determines limiting magnitude • Requirement by LTAO system?

12. LTAO Simulations 2.2 µm 3.7 µm 10 µm AO Only Best case scenario ESO Octopus Simulations/Miska Le Louarn AO + Telescope Only

13. LGS Constellations LGS Constellation • ~insensitive to LGS guide star asterism Easy to provide full clear aperture • NGS position within 30” Simple scheme NGS within METIS FoV Simple scheme NGS 15-30” outside FoV Tomography on NGS outside this range • Not very sensitive to 2x2 or 1x1 NGS scheme But might need to sense e.g. focus for LGS • Faint NGS possible Impact sky background TBD Seems possible to use faint star near Science Target Radius to prevent obscuration NGS brightness NGS off-axis distance • Only photon noise • Vmag =20  100 ph/s • Sky background optimization • J+H+Ks • ~31000ph/s/sq”~2 e-/s/pixels Internal pick-up METIS V~28 V~23

14. Conclusions • METIS requires an AO system to meet its science requirements • Requires both SCAO and LTAO [at first light] • Reaching the diffraction limit (>60% @ N) relatively easy with a simple AO system • High Strehl, Stable PSF very likely • Can use standard components developed for other AO systems • >93% @ N requires more work/full end-to-end investigation • Parallel development of an external LTAO system • Enhancing the sky coverage • Further improving PSF stability in field • Might use internal WFS for Lower Orders and/or NGS tomography • Still much work to do • Full integrated modeling of all effects • Verifying input data atmospheric modeling • Cross-coupling of effects • Impact of telescope vibrations, etc..