High-resolution imaging in the visible on large ground-based telescopes

1. High-resolution imaging in the visible on large ground-based telescopes The Adaptive Optics Lucky Imager Jonathan CrassInstitute of Astronomy, University of Cambridge Craig Mackay, Rafael Rebolo-López, David King, Victor González Escalera, Marta Puga Antolín, Antonio Pérez Garrido, Lucas Labadie, Roberto López, Alex Oscoz, Jorge Andrés Pérez Prieto, Luis Rodríguez-Ramos, Sergio Velasco, Isidro Villo SPIE Astronomical Telescopes and Instrumentation June 2014, Montreal

2. Outline • Motivation and background • The Adaptive Optics Lucky Imager • AO and lucky imaging systems • Optical design & systems • On-sky results • Future work

3. Motivation • How to get diffraction limited imaging in the optical? • Adaptive optics • It’s hard to do AO at optical wavelengths • Lucky imaging • Only works on telescopes up ~2.5m in diameter • Combine the two together – diffraction limited imaging in the visible

4. Adaptive Optics and Lucky Imaging HST - ACS Lucky – 10% Fourier – 20% Fourier – 50%

5. High-Efficiency Lucky Imaging • The sharpest images come from the smallest fraction of images. • Often the poorer quality images are only smeared in one direction. • Garrelet al (PASP, 2012) suggested making the lucky selection in Fourier space rather than image space.

6. High-Efficiency Lucky Imaging High-efficiency lucky imagingMackay 2013, MNRAS, 432, 702

7. About AOLI • Initially for the 4.2m William Herschel Telescope • Lucky Imaging based science instrument: • 4 × 1024 square EMCCDs (E2V CCD201) providing 2000×2000px imaging region • Pixel scale of 18-55 milliarcseconds in I-band • Field of view ranging from 37.5 to 112.5 arcseconds • AO component: • ALPAO 241 actuator deformable mirror (DM241-25) • Non-linear curvature wavefront sensor • Comprises 2 EMCCDs

8. Non-linear Curvature Wavefront Sensor nlCWFS offers: • High sensitivity to low and high orders • Reconstruction with ≈100-1000 fewer photons than conventional techniques Talk 9148-81 – Friday 11:05am (Jonathan Crass)The AOLI low-order non-linear curvature wavefront sensor: laboratory and on-sky results

9. AOLI Optics

10. Wavefront sensor layout

11. Science Camera

12. Poster 9147-294 – Wednesday (Marta Puga Antolín)An atmospheric turbulence and telescope simulator for the development of AOLI Calibration System

13. AOLI at the WHT • The initial run had four key aims: • To collect data from the nlCWFS for post-processing analysis and reconstruction. • To collect data using the science camera to verify its optical quality and sensitivity. • To collect synchronised data between the nlCWFS and science camera to allow comparison between reconstructed wavefronts and the science image. • To collect data with the calibration system to verify its characteristics against on-sky data.

14. AOLI at the WHT

15. AOLI at the WHT

16. On-sky data

17. On-sky data: Real-time lucky

18. On-sky data: Post processing Velasco et al., 2014, MNRAS (In Prep)

19. Summary & Future Work • Summary • The combination of AO and lucky imaging allows diffraction limited imaging in the visible. • The AOLI science camera data matches well with design specification. • Issues experienced on first on-sky run identified and solutions implemented or proposed. • Future Work • Redesign of some mechanisms and supports within instrument to improve performance. • Fully develop AO system to provide diffraction limited imaging at the WHT. • AOLI has the potential to feed not only an imaging camera but also an integral field spectrograph or other instruments. • Aim to revisit the WHT in 2015.