1. The High Altitude Observatory (HAO) at the National Center for Atmospheric Research (NCAR) The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. COSMO Large Coronagraph Preliminary Design Review Site Analysis and Selection Steve Tomczyk National Center for Atmospheric Research Boulder, Colorado – Nov 16, 2015

2. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Site Analysis and Selection Not a site survey Considered only Mauna Loa (ML) and Haleakala (HA) Neither site has been approved for construction Study drew heavily on previous work GONG site survey (included both ML and HA) DKIST site survey (included HA) Published literature Augmented with ML sky brightness, ML seeing, ML particulate measurement

3. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Mauna Loa Site owned and operated by NOAA Active volcano 3353m altitude HAO operation of MLSO since 1965

4. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Haleakala Mees is most likely location for COSMO LC Excellent infrastructure Limited real estate Difficult permitting 3054m altitude

5. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Criteria Considered Sky brightness Aerosol content Clear time fraction Atmospheric seeing Environmental conditions Volcanic and seismic activity Existing infrastructure Permitting Space availability Cost

6. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Sky Brightness

7. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Sky Brightness Monitor Built for DKIST site survey (Lin and Penn, 2004) 9350 measurements at HA taken by DKIST 18546 measurements at ML taken by HAO

8. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Site Analysis and Selection 450nm 530nm 890nm 940nm Both sites are excellent

9. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Aerosols Scattering varies as λ -γ γ = 4 for pure Rayleigh scattering γ = 1 for Mie (aerosol) scattering Higher value of γ = lower aerosol content

10. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Particles Mauna Loa taken by HAOHaleakala taken by DKIST These particle counts are usually associated with clean rooms

11. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Clear Time Fraction ParameterHaleakalaMauna Loa Survey start date7/12/198525/5/1989 Survey end date18/12/199116/9/1993 Days in data set22031576 Fraction of clear time for entire period (“Ca”)55.6558.07 Fraction of clear time after removal of instrumental downtime (“Cw”)64.4364.98 Fitted intercept of site transparency power spectrum-9.33-9.74 Fitted slope of site transparency power spectrum-1.34-1.52 Average extinction coefficients0.09430.0930 Standard deviation in extinction coefficients0.01580.0263 From GONG site survey (Hill et al., 1994)

12. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Shadowing from DKIST at HA

13. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Seeing HA, measured with SHABAR + SDIMM by DKIST ML, measured with SHABAR by HAO Differences unclear Comparison difficult

14. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Seeing MLSO COSMO spatial resolution requirement is 2″ at 1074 nm Seeing budget is 1.67″ Entrance aperture height

15. COSMO PDR (November 16-17, 2015) Site Analysis and Selection Site Analysis Summary ParameterMauna LoaHaleakala Sky Brightness~0.9ppm at 940nm~1.4ppm at 940nm Aerosols  ~ 2.3 (fewer airborne particles)  ~ 1.6 Seeing1.67″ at 15m height Mean seeing is acceptable, but median seeing is not. Difficult to compare with data from Mauna Loa. Observing Time65.0%64.4% Hours lost to shadow067 CleanlinessClass 2500 equivalentClass 10,000 equivalent General Environmental ConditionsBenign temperatures, wind, etc. Volcanic Activity Higher risk of seismic events and magma producing eruptions. Some seismic events possible, but risk is much smaller Permitting Expedited process through NOAA. Some restrictions on materials. Historically difficult and costly Infrastructure Requires upgrade to data lines. However no need to relocate operating COSMO instruments (ChroMag and K-Cor) More developed. Available Building SpaceSpace is availableLimited to ZLO And Mees footprints Both sites acceptable, ML preferred

16. COSMO PDR (November 16-17, 2015) Site Analysis and Selection References H. Lin, M.J. Penn, 2004, “The Advanced Technology Solar Telescope Site Survey Sky Brightness Monitor,” PASP, 116:652 F. Hill et. al., 1994, ”The Global Oscillation Network Group Site Survey Part II.: Results,” Solar Physics 152:351 F. Hill et al., 2004, “ATST Site Survey Working Group Final Report”, ATST Report 21. S. Tomczyk and D.F. Elmore, “Sky Brightness at Mauna Loa and Haleakala”, 2015, COSMO Technical Note #9. S. Tomczyk, “HAO SHABAR Instrument and Observations”, 2013, COSMO Tech Note #19. S. Tomczyk, “COSMO Site Cleanliness Report”, 2015, COSMO Technical Note #26. S. Tomczyk, P. Oakley and P.G. Nelson, 2015, “COSMO Large Coronagraph Site Evaluation and Selection”, COSMOLC-DE-7400.