Preliminary results of aperture-area comparison for exo-atmospheric solar irradiance

Abstract

Exo-atmospheric solar irradiance measurements made by the solar irradiance community over the past 25 years incorporated limiting apertures measured by a number of metrology laboratories using a variety of techniques. Knowledge of the aperture area is a critical component in the conversion of radiant flux measurements to solar irradiance. An Earth Observing System (EOS)-sponsored international comparison of aperture area measurements of limiting apertures provided by solar irradiance researchers is under way, the effort being executed by the National Institute of Standards and Technology (NIST) in coordination with the EOS Project Science Office. Apertures that have institutional heritage with historical solar irradiance measurements are measured using the absolute aperture measurement facility at NIST. The measurement technique employs non-contact video microscopy using a high-precision stage. The aperture area comparison aims to quantify the relative differences between the participating institutions' aperture area measurements. Preliminary results of the comparison will be reported.