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    ASTM G177 - 03(2012)

    Standard Tables for Reference Solar Ultraviolet Spectral Distributions: Hemispherical on 37° Tilted Surface

    Active Standard ASTM G177 | Developed by Subcommittee: G03.09

    Book of Standards Volume: 14.04

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    Significance and Use

    5.1 This standard does not purport to address the mean level of solar ultraviolet spectral irradiance to which materials will be subjected during their useful life. The spectral irradiance distributions have been chosen to represent a reasonable upper limit for natural solar ultraviolet radiation that ought to be considered when evaluating the behavior of materials under various exposure conditions.

    5.2 Absorptance, reflectance, and transmittance of solar energy are important factors in material degradation studies. These properties are normally functions of wavelength, which require that the spectral distribution of the solar flux be known before the solar-weighted property can be calculated.

    5.3 The interpretation of the behavior of materials exposed to either natural solar radiation or ultraviolet radiation from artificial light sources requires an understanding of the spectral energy distribution employed. To compare the relative performance of competitive products, or to compare the performance of products before and after being subjected to weathering or other exposure conditions, a reference standard solar spectral distribution is desirable.

    5.4 A plot of the SMARTS2 model output for the reference hemispherical UV radiation on a 37° south facing tilted surface is shown in Fig. 1. The input needed by SMARTS2 to generate the spectrum for the prescribed conditions are shown in Table 1.

    Total Hemispherical Ultraviolet Reference Spectra Based
on SMARTS2 Runs for AM1.05 UV Spectral Profile (a) Linear Scale; (b)
Logarithmic Scale
    FIG. 1 Total Hemispherical Ultraviolet Reference Spectra Based on SMARTS2 Runs for AM1.05 UV Spectral Profile (a) Linear Scale; (b) Logarithmic Scale
    TABLE 1 SMARTS Version 2.9.2 Input File to Generate the Reference Spectra

    Card ID


    Parameter/Description/Variable Name


    'ASTM UV_Std_Spectra'




    Pressure input mode (1 = pressure and altitude): ISPR


    820.0 2.0.

    Station Pressure (mb) and altitude (km): SPR, ALT



    Standard Atmosphere Profile Selection (1 = use default atmosphere): IATM1



    Default Standard Atmosphere Profile: ATM



    Water Vapor Input (1 = default from Atmospheric Profile): IH2O



    Ozone Calculation (0 = user input concentariont and altitude): IO3


    1 0.3

    Ozone Atltitude correctiom (IALT = 1 = > correct from sea level), Ozone Concentration (AbO3 = 0.30 atm cm)



    Pollution level mode (1 = standard conditions/no pollution): IGAS (see X1.3)



    Carbon Monoxide volume mixing ratio (ppm): qCO2 (see X1.3)



    Extraterrestrial Spectrum (1 = SMARTS/Gueymard): ISPCTR



    Aerosol Profile to Use: AEROS



    Specification for aerosol optical depth/turbidity input (0 = AOD at 500 nm): ITURB



    Aerosol Optical Depth at 500 nm: TAU5



    Far field Spectral Albedo file to use (38 = Light Sandy Soil): IALBDX



    Specify tilt calculation (1 = yes): ITILT


    38 37 180

    Albedo and Tilt variables—Albedo file to use for near field, Tilt, and Azimuth: IALBDG, TILT, WAZIM


    280 400 1.0 1367.0

    Wavelength Range—start, stop, mean radius vector correction, integrated solar spectrum irradiance: WLMN, WLMX, SUNCOR, SOLARC



    Separate spectral output file print mode (2 = yes): IPRT


    280 400 0.5

    Output file wavelength-Print limits, start, stop, minimum step size: WPMN, WPMX, INTVL



    Number of output variables to print: IOTOT



    Code relating output variables to print [8 = Hemispherical tilt, OUT(8)]



    Circumsolar calculation mode (1 = yes): ICIRC


    0 2.9 0

    Receiver geometry-Slope, View, Limit half angles: SLOPE, APERT, LIMIT



    Smooth function mode (0 = none): ISCAN



    Illuminance calculation mode (0 = none): ILLUM



    UV calculation mode (0 = none): IUV



    Solar Geometry mode (2 = Air Mass): IMASS



    Air mass value: AMASS

    5.5 SMARTS2 Version 2.9.2 is required to generate AM 1.05 UV reference spectra.

    5.6 The availability of the adjunct standard computer software (ADJG173CD5) for SMARTS2 allows one to (1) reproduce the reference spectra, using the above input parameters; (2) compute test spectra to attempt to match measured data at a specified FWHM, and evaluate atmospheric conditions; and (3) compute test spectra representing specific conditions for analysis vis-à-vis any one or all of the reference spectra.

    1. Scope

    1.1 The table provides a standard ultraviolet spectral irradiance distribution that maybe employed as a guide against which manufactured ultraviolet light sources may be judged when applied to indoor exposure testing. The table provides a reference for comparison with natural sunlight ultraviolet spectral data. The ultraviolet reference spectral irradiance is provided for the wavelength range from 280 to 400 nm. The wavelength region selected is comprised of the UV-A spectral region from 320 to 400 nm and the UV-B region from 280 to 320 nm.

    1.2 The table defines a single ultraviolet solar spectral irradiance distribution:

    1.2.1 Total hemispherical ultraviolet solar spectral irradiance (consisting of combined direct and diffuse components) incident on a sun-facing, 37° tilted surface in the wavelength region from 280 to 400 nm for air mass 1.05, at an elevation of 2 km (2000 m) above sea level for the United States Standard Atmosphere profile for 1976 (USSA 1976), excepting for the ozone content which is specified as 0.30 atmosphere-centimeters (atm-cm) equivalent thickness.

    1.3 The data contained in these tables were generated using the SMARTS2 Version 2.9.2 atmospheric transmission model developed by Gueymard (1,2).

    1.4 The climatic, atmospheric and geometric parameters selected reflect the conditions to provide a realistic maximum ultraviolet exposure under representative clear sky conditions.

    1.5 The availability of the SMARTS2 model (as an adjunct (ADJG173CD3) to this standard) used to generate the standard spectra allows users to evaluate spectral differences relative to the spectra specified here.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    E490 Standard Solar Constant and Zero Air Mass Solar Spectral Irradiance Tables

    E772 Terminology of Solar Energy Conversion

    ICS Code

    ICS Number Code 17.180.20 (Colours and measurement of light)

    UNSPSC Code

    UNSPSC Code

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/G0177-03R12

    ASTM International is a member of CrossRef.

    Citation Format

    ASTM G177-03(2012), Standard Tables for Reference Solar Ultraviolet Spectral Distributions: Hemispherical on 37° Tilted Surface, ASTM International, West Conshohocken, PA, 2012,

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