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Measuring Turbulence in Domes

Measuring Turbulence in Domes. Jeff Fines University of Hawai‘i, Manoa - BSEE Craig Nance W.M. Keck Observatory 25 July 2008. Overview. Background Initial Tasks Redesign Deployment Obtained Data Conclusion. 1. Fig. 1: Astronomical Seeing. Fig. 2: DBSAS. Background.

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Measuring Turbulence in Domes

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  1. Measuring Turbulence in Domes Jeff Fines University of Hawai‘i, Manoa - BSEE Craig Nance W.M. Keck Observatory 25 July 2008

  2. Overview Background Initial Tasks Redesign Deployment Obtained Data Conclusion 1

  3. Fig. 1: Astronomical Seeing Fig. 2: DBSAS Background Scintillation and Seeing Turbulence Temperature Gradients Stirring Atmosphere In-Dome Seeing Displaced-Beam Small Aperture Scintillometer (DBSAS) Structure Constant Goal Summit Installation Feasible? 2

  4. RX TX Fig. 4: Basic System *not drawn to scale Fig. 3: Pathways Initial Work Unpack & Install Familiarization DBSAS Set-Up Point-to-point, 2- and 3-path System Design 3

  5. Fig. 5: Initial Configuration in Keck II Dome Fig. 6: Lowest Structure Constant Observed Initial Deployment Unique Opportunity 2nd Week Obtained Data 6:49pm - 9:18pm Observed Sensitivity of System 5.56∙10-16 m-2/3 over 63 m path Rated Sensitivity of System 10-16 m-2/3 over 100 m path 4

  6. Fig. 7: System Alignment Fig. 8: Ideal strength for minimum error Technical Difficulties Measurement Snag Cycled System Checked Connections System Alignment 2 Person Requirement SENSITIVE Signal Strength Ch. 1 – Yellow Ch. 2 – Green 5

  7. Fig. 10: Angle Compensation Fig. 9: Before and After *not drawn to scale Redesign Easy Set-Up More Compact Angle Correction New Cable RS-485 Summit Simulation 6

  8. 21 m

  9. Fig. 11: Structure Constant over Time Fig. 12a: Log Linear Relationship is “suggested” Fig. 12b: Correlation from first deployment Analyzing the Data Day-Time Data 12:13pm – 3:20pm Observed Correlation Inner Scale of Refractive Index Fluctuations Small sample of data “Suggested” Log Linear Relation 8

  10. Fig. 13: System on Cabinet Conclusion Robust System Improved Reliability Appliance-Like Sensitive System Calibration Maintenance Installation is feasible New Location Trained Operator 9

  11. Acknowledgements W.M. Keck Observatory Craig Nance Sarah Anderson Hualalai Warehouse Crew HQ Mechanical Shop Summit Crew Akamai Internship Program Lynne Raschke, Scott Seagroves, David Le Mignant Center for Adaptive Optics, NSF Grant Scintec Bettina Schrauf, Todd Reed TMT Tony Travouillon The Akamai Internship Program is funded by the Center for Adaptive Optics through its National Science Foundation Science and Technology Center grant (#AST-987683). 10

  12. Thank You

  13. Full-Width Half-Maximum (FWHM) FWHM = [ (CN2∙H) / (6.8∙10-13) ]0.6π Where CN2 = Structure Constant H = Path Length π = the unit for arc sec a

  14. Conclusion Has Objective been fulfilled? Summarize findings. What is to come next for the DBSAS? 9

  15. Rated Sensitivity of System: 10-16 m-2/3 over 100 m path Observed Sensitivity of System: 5.56∙10-16 m-2/3 over 63 m path Ratio of Rated to Observed: 1 to 8.825 Analyzing the Data **Description of graph. **What does it all mean?? Fig. 5: Initial Configuration 7

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