1. Vacuum System Vibration Analysis on the Keck Telescopes Michael Cooney W.M. Keck Observatory

2. Background Secondary Mirror Secondary Mirror Vacuum System Vacuum System Why Reduce Vibrations Why Reduce Vibrations Creating Test Plans Creating Test Plans

3. The Job Test Setup Test Setup Data Collection Data Collection Data Reduction Data Reduction Data Analysis Data Analysis

4. Test Conditions Keck 1 and 2 Keck 1 and 2 Taking Data Taking Data Two Regulators Two Regulators

5. Keck 1 Secondary Mirror Acceleration Average acceleration is less, especially at higher frequency Average acceleration is less, especially at higher frequency 80 Degree Elevation Pink: Old System Blue: New System

6. Keck 1 Displacements Displacement larger with the new regulator at 15Hz and 19Hz Displacement larger with the new regulator at 15Hz and 19Hz 80 Degree Elevation Dark colors: Old System Light colors: New System

7. Keck 1 Mirror Movement Mirror is pistoning at low frequencies Mirror is pistoning at low frequencies Mirror is tilting in y at low frequencies Mirror is tilting in y at low frequencies Piston Effect: Pink is New; Blue is OldTip-Tilt Effect: Pink is New; Blue is Old

8. Keck 2 Secondary Mirror Acceleration Average acceleration is less Average acceleration is less Acceleration around 20 Hz is larger Acceleration around 20 Hz is larger Dark Colors: Old System Light Colors: New System

9. Results Keck 2 Above 30Hz frequency shows less displacement Above 30Hz frequency shows less displacement Concerned with displacements between 10Hz and 30Hz Concerned with displacements between 10Hz and 30Hz 80 Degree Elevation Yellow: Old System Pink: New System

10. Keck 2 Mirror Movement Mirror is pistoning at low frequencies Mirror is pistoning at low frequencies Mirror is tilting in y at low frequencies Mirror is tilting in y at low frequencies Piston Effect: Pink is New; Blue is OldTip-Tilt Effect: Pink is New; Blue is Old

11. Conclusions Keck 1 Keck 1: Keck 1: Unexpected pistoning, tip-tilt, and displacements are larger Unexpected pistoning, tip-tilt, and displacements are larger Acceleration is less Acceleration is less Amplified natural resonance of telescope Amplified natural resonance of telescope Stiffer structure? Stiffer structure? Coupling issue to contend with Coupling issue to contend with More tests to verify data More tests to verify data

12. Conclusions Keck 2 Keck 2: Keck 2: Displacements on a whole are acceptable Displacements on a whole are acceptable Pistoning and tip-tilt are mostly same or lower Pistoning and tip-tilt are mostly same or lower Acceleration mostly lower Acceleration mostly lower Feed forward system to take out displacement Feed forward system to take out displacement

13. Acknowledgements Jason Chin Jason Chin Dwight Chan Dwight Chan Ed Wetherell Ed Wetherell Sarah Anderson Sarah Anderson Malika Bell Malika Bell W.M. Keck Observatory W.M. Keck Observatory Center for Adaptive Optics Center for Adaptive Optics University of Hawaii-Manoa University of Hawaii-Manoa Funding provided through the Center for Adaptive Optics, a National Science Foundation Science and Technology Center (STC), AST-987683 Funding provided through the Center for Adaptive Optics, a National Science Foundation Science and Technology Center (STC), AST-987683