1. Laser guide star adaptive optics at the Keck Observatory Adam R. Contos, Peter L. Wizinowich, Scott K. Hartman, David Le Mignant, Christopher R. Neyman, Paul J. Stomski, Jr., and Douglas Summers W.M. Keck Observatory SPIE Astronomical Telescopes and Instrumentation Conference 23 August 2002, Waikoloa, HI 4389 - 42

2. Talk Outline  Overview  Sky Coverage for LGS and NGS Modes  Optical Path  New LGS AO Hardware  System Upgrades & Issues  Laser Guide Star  Future  Summary

3. Overview  Traditional AO with NGS –Bright star in close proximity ~ 1% coverage –Sodium LGS for nearly complete coverage Still require an NGS, but can be much dimmer  Keck II System Upgrades for LGS AO –Low Bandwidth Wavefront Sensor (LBWFS) –Tip/Tilt Sensor (TTS), using quad-cell APDs –Software control –Laser system (described in following talk)  Scheduled for integration in 2003

4. Sky Coverage: NGS and LGS 1 Bahcall & Soneira, 1981; 2 Keck Report 208, 1996. NGS LGS

5. Optical Path Highlighted AO Bench Elements: 1-Image Rotator 2-Tip/Tilt Mirror 4-Deformable Mirror 6-IR Dichroic 12-Sodium Dichroic 13-Field Steering Mirrors 14, 15-Wavefront Sensing Camera and Focus Camera Stage 17-Beamsplitter 18-Low Bandwidth Wavefront Sensor, Tip/Tilt Sensor & Stage 19-Acquisition Camera

6. LBWFS & TTS Description  Low Bandwidth Wavefront Sensor –Shack-Hartmann lenslet array sensor –304 subapertures (240 active) –Photometrics 512x512 CCD detector –Readout every few sec. to few min.  Tip/tilt Sensor –Quad-lens –Fiber-fed APDs  Mounted on 3-axis tip/tilt stage  Beamsplitter cube –90% to TTS, 10% to LBWFS

7. System Upgrades & Issues (1)

8. System Upgrades & Issues (2)

9. System Upgrades & Issues (3)

10. 1st Laser Propagation (12/01)  Laser power ~ 17 W  FWHM ~ 1.4” (seeing ~ 1”)  Magnitude ~ 9.5

11. Future

12. Summary of LGS AO at Keck  Achieved first laser propagation  AO upgrades being incorporated for LGS  Integration milestones throughout 2003 –LGS AO on world’s largest optical telescope will become incredible tool for astronomy –First operational LGS on an 8-10 m telescope

14. System Flow & Control