Results of aperture area comparisons for exo-atmospheric total solar irradiance measurements.

Exo-atmospheric solar irradiance measurements made by the solar irradiance community since 1978 have incorporated limiting apertures with diameters 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. A National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) sponsored international comparison of aperture area measurements of limiting apertures provided by solar irradiance researchers was performed, the effort being executed by the National Institute of Standards and Technology (NIST) in coordination with the EOS Project Science Office.

An Oil-Bath-Based 293 K to 473 K Blackbody Source.

A high temperature oil-bath-based-black-body source has been designed and constructed in the Radiometric Physics Division at the National Institute of Standards and Technology, Gaithersburg, MD. The goal of this work was to design a large aperture blackbody source with highly uniform radiance across the aperture, good temporal stability, and good reproducibility. This blackbody source operates in the 293 K to 473 K range with blackbody temperature combined standard uncertainties of 7.

A Third Generation Water Bath Based Blackbody Source.

A third generation water bath based black-body source has been designed and constructed in the Radiometric Physics Division at the National Institute of Standards and Technology, Gaithersburg, MD. The goal of this work was to design a large aperture blackbody source with improved temporal stability and reproducibility compared with earlier designs, as well as improved ease of use. These blackbody sources operate in the 278 K to 353 K range with water temperature combined standard uncertainties of 3.

High Accuracy Measurement of Aperture Area Relative to a Standard Known Aperture.

Precise knowledge of the area of apertures used in high precision radiometry is extremely important. A method is presented here for the determination of the area of round and irregularly shaped apertures by comparison to a standard aperture which has been measured by other means to high accuracy. The method presented here is quick and has no physical contact with the fragile edge of the aperture opening.