Experimental determination of the reference plane of shaped diffusers by solar ultraviolet measurements

Gröbner, Julian; Blumthaler, M.

doi:10.1364/ol.32.000080

Cited by 12 publications

(14 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…By adapting calculations performed for similar diffusers [ Bernhard and Seckmeyer , 1997; Hovila et al , 2005], we estimated that the reference plane for irradiance calibrations could be about 2 mm behind the diffuser's top. Recent experimental evidence conflicts with theoretical calculations, indicating that the offset for shaped diffusers may exceed the height of the diffuser [ Manninen et al , 2006; Gröbner and Blumthaler , 2007]. Preliminary tests with the UV9 diffuser have indicated that its reference plane could be as much as 5 mm behind the diffuser's top.…”

Section: Discussionsupporting

confidence: 55%

Comparison of ultraviolet spectroradiometers in Antarctica

et al. 2008

View full text Add to dashboard Cite

[1] Solar ultraviolet irradiance has been monitored in Antarctica for almost two decades by a network of spectroradiometers established by the National Science Foundation. Data have been used for investigating increases in ultraviolet radiation in response to ozone depletion, validation of satellite observations, and the establishment of ultraviolet radiation climatologies and trends. To assess the quality of data collected, measurements of the monitoring spectroradiometer installed at Arrival Heights (78°S, 167°E) were compared with an independently calibrated, state-of-the art instrument, which was installed next to the monitoring system for a three-month campaign. Measurements of the two instruments differed by 5-7% on average. The discrepancy is quantitatively explained by the different irradiance scales used by the two systems, a bias in determining the reference plane of fore-optics, drifts of calibration standards, some temperature-dependence in the transmission of the entrance optics, and nonlinearity of one of the systems. The wavelength accuracy of data from both instruments was also tested with two commonly used correlation methods. Wavelength shifts determined with the two methods agreed to within 0.003-0.006 nm. Results of the campaign suggest that data collected by the monitoring instrument are of adequate quality for submission to the Network for the Detection of Atmospheric Composition Change.

show abstract

Section: Discussionsupporting

confidence: 55%

Comparison of ultraviolet spectroradiometers in Antarctica

et al. 2008

View full text Add to dashboard Cite

show abstract

“…Similar findings based on solar ultraviolet (UV) irradiance measurements were reported for a dome-shaped diffuser of type J1002 commonly used in solar UV spectroradiometers [3]. It is of great importance, particularly for the international quality assurance projects of monitoring solar UV irradiance [4][5][6][7], to improve the accuracy of the distance determination to be able to calibrate the spectroradiometers as reliably as possible.…”

Section: Introductionsupporting

confidence: 69%

“…In the earlier analyses of the diffuser reference planes, the angular responsivities were assumed to be cosinusoidal and the sources and detectors were assumed to be spatially uniform [1]. The point-source and point-detector approximation was used in [2,3]. However, the radiation sources used were approximately rectangular and some of the diffusers were noted to have significantly noncosinusoidal angular responsivities [1].…”

Section: Introductionmentioning

confidence: 99%

Determining the irradiance signal from an asymmetric source with directional detectors: application to calibrations of radiometers with diffusers

Manninen¹,

Kärhä²,

Ikonen³

2008

Appl. Opt.

View full text Add to dashboard Cite

The energy transfer integral between radiating rectangular and detecting circular parallel plates having nonideal angular characteristics is solved for modeling the distance dependence of the irradiance signal. The equation derived for the irradiance signal, which is called the modified inverse-square law, depends on the position, shape, size, and angular characteristics of the light source and the detector. We apply the new model equation to the calibration of a spectroradiometer to determine accurately the distance offsets, which fix the positions of the effective receiving apertures of diffusers used in the entrance optics of spectroradiometers. Earlier measurement results, e.g., for solar UV irradiance, may include uncorrected effects and can be corrected reliably as diffuser offsets and other correction factors are determined with the modified inverse-square law. Simplifications of the modified inverse-square law for analyzing the distance offsets and the correction factors are studied. Simplified equations for the diffuser offset analysis may be used without losing the accuracy when the cosine response of the diffuser is reasonably good. However, for diffusers whose angular responsivities deviate much from the cosinusoidal angular responsivity, large approximation errors in the diffuser offset values may appear if the angular effects are not properly taken into account.

show abstract

“…No temperature correction was necessary for the ATI diffuser because it is heated to about 20°C. The ATI analysis also includes a correction for the shape of the diffuser, which affects the measurement of the distance between the lamp and the diffuser during calibrations (Gröbner and Blumthaler 2007). This resulted in a 1.5% decrease of data.…”

Section: B Comparison Of Spectral Irradiancementioning

confidence: 99%

Spectral UV Measurements of Global Irradiance, Solar Radiance, and Actinic Flux in New Zealand: Intercomparison between Instruments and Model Calculations

Blumthaler

Schallhart

Schwarzmann

et al. 2008

Journal of Atmospheric and Oceanic Technology

Self Cite

View full text Add to dashboard Cite

Presented here are the results of a short but intense measurement campaign at Lauder, New Zealand, in which spectral irradiance from instruments operated by the National Institute of Water and Atmospheric Research (NIWA) and Austria/Innsbruck (ATI) were traced to different irradiance standards and compared. The observed spectral differences for global irradiance were relatively small (Ͻ5%) and were consistent with those expected from observed differences in the radiation standards used by each group. Actinic fluxes measured by both groups were also intercompared and found to agree at the 10% level. The ATI instrument had the additional capability of measuring solar direct beam irradiance and sky radiances. These provided the first series of sky radiance measurements at this pristine Network for the Detection of Atmospheric Composition Change (NDACC) site. The polarization of sky radiance results were compared with estimates from a radiative transfer model without any aerosols and was found to be up to 25% smaller. Total ozone values derived from Total Ozone Mapping Spectrometer (TOMS), Dobson measurements by NIWA, spectral direct sun measurements by ATI, and spectral global irradiance measurements by NIWA agreed generally within 2%-3%.

show abstract

Experimental determination of the reference plane of shaped diffusers by solar ultraviolet measurements

Cited by 12 publications

References 3 publications

Comparison of ultraviolet spectroradiometers in Antarctica

Comparison of ultraviolet spectroradiometers in Antarctica

Determining the irradiance signal from an asymmetric source with directional detectors: application to calibrations of radiometers with diffusers

Spectral UV Measurements of Global Irradiance, Solar Radiance, and Actinic Flux in New Zealand: Intercomparison between Instruments and Model Calculations

Contact Info

Product

Resources

About