A scale of spectral irradiance has been realized for the 400-700-nm wavelength range based on absolute silicon photodetectors, with the wavelength selected by interference filters. From these data a photometric scale of luminous intensity has been realized. The results were compared to scales based on blackbodies.
The stability of commercial 400W high pressure sodium lamps has been studied to allow the selection of lamps that produce a stable luminous flux on relighting. The properties of the lamps have been studied during the first minutes of starting, their output on relighting in place, and their output after 100' s of hours burning. Lamps have been selected that repeat to + 1% on relighting, and are expected to remain that stable over a life of about 450 hours. The lamps have been calibrated for total luminous flux by sphere comparison, with an uncertainty of +4.6%. These lamps will be used as working standards, and goniometric measurements will be made to reduce the uncertainty.
As part of the Environmental Protection Agency's stratospheric ozone program, the Atmospheric Research and Exposure Assessment Laboratory of the EPA (AREAL) has been given the responsibility of standardizing absolute measurements of incident ultra-violet radiation being obtained by various environmental research activities, both within and outside of EPA. Of primary interest are quantitative UV radiation flux measurements in the environmentally active wavelength range of 280 to 400 nm, including the UV-B range. Measurements of UV-B radiation are associated with a wide variety of research activities endeavoring to quantitatively relate exposure to incident UV radiant energy intensity - particularly changes or effects on human health and on the various environmental ecosystems. A significant amount of UV-B measurement activity in the scientific community is currently underway or is being planned. Currently, many of the UV-B measurements suffer from substantial lack of comparability and credibility due to wide variations in the quality and calibration accuracy of the UV-B measurement instruments used. To ensure that measurements throughout these activities are of known quality, a quality assurance program should be developed. One of the first steps to ensure known data accuracy is to establish a measurement standard for the monitoring instrumentation.
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