COSMO Site and Design Advancement (COSADA)

Principal Investigator: Maurice Wilson

Institution name: National Center for Atmospheric Research (NCAR) High Altitude Observatory

Scientific Objetives

COSMO will be an observatory housing the Large Coronagraph, which will have a 1.5-meter aperture in order to study the magnetic field behavior of the Sun’s corona.  An international site survey has commenced to determine which regions around the world provide favorable weather conditions and climate for such an observatory to gather precise data when observing the Sun.  The primary conditions of interest for the current phase of the site survey include the local wind dynamics and local aerosol abundance.   Amongst many meteorological parameters, the local wind velocity and aerosol optical depth will be used to compare the Sun-observing conditions between various sites.

After assessing six potential sites, in the second phase of the project, NCAR has narrowed potential COSMO locations to the following locations: Magdalena Ridge Observatory (New Mexico), Cerro Tololo Inter-American Observatory (Chile) and Teide Observatory (Izaña, Spain). These sites were selected based on scientific viability, including weather, sky brightness, and other considerations. NSF NCAR will continue working with communities at those three sites as data assessment continues. During this second phase, NCAR will be in close contact with the sites to ensure the suitability of the site. The project goal is to link coronagraphic measurements of near-Sun radiance with aerosol-constrained inferences derived from direct-Sun and sky photometry. In this sense, the comparability between photometric measurements done with different photometric instruments (Cimel-AERONET and Prede-Skynet) is critical.

Future plans involved working on Cimel-Prede comparability as well as performing a joint diagnostics of circumsolar sky brightness using coronagraphic measurements and aerosol optical inversions at Izaña.