Abstract

During the late Seventies a second generation of absolute cavity radiometers based on the principle of substitution of electrical power for radiative power was developed for solar radiometry. The operating principle and details of the realization of this new radiometer (PMO6-type) are described. To better understand these instruments and to improve their accuracy, the main effort was concentrated on the development of independent laboratory experiments to characterize them. It is demonstrated that this characterization allows an accuracy of solar radiometry of 0.12% from space and of 0.17% from the ground.

© 1986 Optical Society of America

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References

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  1. J. M. Kendell, C. M. Berdahl, “Two Blackbody Radiometers of High Accuracy,” Appl. Opt. 9, 1082 (1970).
    [CrossRef]
  2. R. C. Willson, “New Radiometric Techniques and Solar Constant Measurements,” Sol. Energy 14, 203 (1973).
    [CrossRef]
  3. J. Geist, “Fundamental Principles of Absolute Radiometry and the Philosophy of This NBS Program (1968–1971),” Natl. Bur. Stand. U.S. Tech. Note 594-1 (1972).
  4. R. W. Brusa, C. Frohlich, “Realization of Absolute Scale of Total Irradiance,” in Scientific Discussions, Fourth International Pyrheliometer Comparisons, Davos (1975), p. 35.
  5. D. Crommelynck, “Theorie Instrumentale en Radiometrie Absolue,” Institut Royal Meteorologique de Belgique, Serie A, 81 (1973).
  6. C. Fröhlich, J. Geist, J. M. Kendall, R. M. Marchgraber, “The Third International Comparisons of Pyrheliometers and a Comparison of Radiometric Scales,” Sol. Energy 14, 157 (1973).
  7. W. R. Blevin, J. Geist, “Infrared Reflectometry with a Cavity-Shaped Pyroelectric Detector,” Appl. Opt. 13, 2212 (1974).
    [CrossRef] [PubMed]
  8. R. W. Brusa, “Lommel’s Theory of Diffraction and Absolute Radiometry,” in Symposium, Sixth International Pyrheliometer Comparisons, Davos (1985), p. 37.
  9. R. W. Brusa, “Solar Radiometry,” ETHZ Dissertation 7181, Zurich (1983).
  10. E. J. Gillham, “Recent Investigations in Absolute Radiometry,” Proc. R. Soc. London Ser. A 269, 249 (1962).
    [CrossRef]
  11. “Technical Regulations,” World Meteorological Organization, WMO 49, Geneva (1981).

1974 (1)

1973 (3)

R. C. Willson, “New Radiometric Techniques and Solar Constant Measurements,” Sol. Energy 14, 203 (1973).
[CrossRef]

D. Crommelynck, “Theorie Instrumentale en Radiometrie Absolue,” Institut Royal Meteorologique de Belgique, Serie A, 81 (1973).

C. Fröhlich, J. Geist, J. M. Kendall, R. M. Marchgraber, “The Third International Comparisons of Pyrheliometers and a Comparison of Radiometric Scales,” Sol. Energy 14, 157 (1973).

1972 (1)

J. Geist, “Fundamental Principles of Absolute Radiometry and the Philosophy of This NBS Program (1968–1971),” Natl. Bur. Stand. U.S. Tech. Note 594-1 (1972).

1970 (1)

1962 (1)

E. J. Gillham, “Recent Investigations in Absolute Radiometry,” Proc. R. Soc. London Ser. A 269, 249 (1962).
[CrossRef]

Berdahl, C. M.

Blevin, W. R.

Brusa, R. W.

R. W. Brusa, C. Frohlich, “Realization of Absolute Scale of Total Irradiance,” in Scientific Discussions, Fourth International Pyrheliometer Comparisons, Davos (1975), p. 35.

R. W. Brusa, “Lommel’s Theory of Diffraction and Absolute Radiometry,” in Symposium, Sixth International Pyrheliometer Comparisons, Davos (1985), p. 37.

R. W. Brusa, “Solar Radiometry,” ETHZ Dissertation 7181, Zurich (1983).

Crommelynck, D.

D. Crommelynck, “Theorie Instrumentale en Radiometrie Absolue,” Institut Royal Meteorologique de Belgique, Serie A, 81 (1973).

Frohlich, C.

R. W. Brusa, C. Frohlich, “Realization of Absolute Scale of Total Irradiance,” in Scientific Discussions, Fourth International Pyrheliometer Comparisons, Davos (1975), p. 35.

Fröhlich, C.

C. Fröhlich, J. Geist, J. M. Kendall, R. M. Marchgraber, “The Third International Comparisons of Pyrheliometers and a Comparison of Radiometric Scales,” Sol. Energy 14, 157 (1973).

Geist, J.

W. R. Blevin, J. Geist, “Infrared Reflectometry with a Cavity-Shaped Pyroelectric Detector,” Appl. Opt. 13, 2212 (1974).
[CrossRef] [PubMed]

C. Fröhlich, J. Geist, J. M. Kendall, R. M. Marchgraber, “The Third International Comparisons of Pyrheliometers and a Comparison of Radiometric Scales,” Sol. Energy 14, 157 (1973).

J. Geist, “Fundamental Principles of Absolute Radiometry and the Philosophy of This NBS Program (1968–1971),” Natl. Bur. Stand. U.S. Tech. Note 594-1 (1972).

Gillham, E. J.

E. J. Gillham, “Recent Investigations in Absolute Radiometry,” Proc. R. Soc. London Ser. A 269, 249 (1962).
[CrossRef]

Kendall, J. M.

C. Fröhlich, J. Geist, J. M. Kendall, R. M. Marchgraber, “The Third International Comparisons of Pyrheliometers and a Comparison of Radiometric Scales,” Sol. Energy 14, 157 (1973).

Kendell, J. M.

Marchgraber, R. M.

C. Fröhlich, J. Geist, J. M. Kendall, R. M. Marchgraber, “The Third International Comparisons of Pyrheliometers and a Comparison of Radiometric Scales,” Sol. Energy 14, 157 (1973).

Willson, R. C.

R. C. Willson, “New Radiometric Techniques and Solar Constant Measurements,” Sol. Energy 14, 203 (1973).
[CrossRef]

Appl. Opt. (2)

Institut Royal Meteorologique de Belgique, Serie A (1)

D. Crommelynck, “Theorie Instrumentale en Radiometrie Absolue,” Institut Royal Meteorologique de Belgique, Serie A, 81 (1973).

Natl. Bur. Stand. U.S. Tech. Note 594-1 (1)

J. Geist, “Fundamental Principles of Absolute Radiometry and the Philosophy of This NBS Program (1968–1971),” Natl. Bur. Stand. U.S. Tech. Note 594-1 (1972).

Proc. R. Soc. London Ser. A (1)

E. J. Gillham, “Recent Investigations in Absolute Radiometry,” Proc. R. Soc. London Ser. A 269, 249 (1962).
[CrossRef]

Sol. Energy (2)

R. C. Willson, “New Radiometric Techniques and Solar Constant Measurements,” Sol. Energy 14, 203 (1973).
[CrossRef]

C. Fröhlich, J. Geist, J. M. Kendall, R. M. Marchgraber, “The Third International Comparisons of Pyrheliometers and a Comparison of Radiometric Scales,” Sol. Energy 14, 157 (1973).

Other (4)

R. W. Brusa, “Lommel’s Theory of Diffraction and Absolute Radiometry,” in Symposium, Sixth International Pyrheliometer Comparisons, Davos (1985), p. 37.

R. W. Brusa, “Solar Radiometry,” ETHZ Dissertation 7181, Zurich (1983).

R. W. Brusa, C. Frohlich, “Realization of Absolute Scale of Total Irradiance,” in Scientific Discussions, Fourth International Pyrheliometer Comparisons, Davos (1975), p. 35.

“Technical Regulations,” World Meteorological Organization, WMO 49, Geneva (1981).

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Figures (4)

Fig. 1
Fig. 1

Mechanical drawing of the PMO6 absolute radiometer. In front of the detector, in good thermal contact, is the so-called muffler. It defines an infrared reference for the cavity, reduces scattered light, and protects the receiver from the effect of wind. In front of it are the shutter and a view-limiting aperture. The distance between the view-limiting and the detector aperture is 95.4 mm, yielding a viewing angle of 5° and a slope angle of 1°. The weight of the instrument is 1600 g.

Fig. 2
Fig. 2

Schematic drawing of the PMO-6 detector with its control electronics. The detector consists of two electrically calibrated heat flux transducers with cavities. The cavity placed behind the precison aperture is used to substitute radiation power by electrical power. The rear cavity serves to compensate for changes of the environmental conditions. The servo loop keeps the temperature difference between the cavities constant by controlling the square root of the current, which is proportional to the electrical power dissipated.

Fig. 3
Fig. 3

Setup for the determination of the radiation losses of the cavity. The reflectometer is made out of PVF film coated with gold black on its front and metallic gold on its rear face. The film is supported by a cone-shaped brass sheet and forms a pyroelectric detector.7

Fig. 4
Fig. 4

Results of the determination of the frequency-dependent losses of radiation of the cavity for two instruments. Shown are the phase and amplitude of the measurements with radiative and electrical excitation. They are normalized to the power of the excitation. Positive phase means that the detector signal leads the input. As determined from the difference between radiative and electrical measurements, the losses of radiation amount to 250 and 425 ppm for the two radiometers, respectively. Note that the phase of the electrical measurement is due to the thermal excitation of the cavity, whereas the phase of the radiative measurement is dominated by the signal of reflected radiation.

Tables (2)

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Table I Results of Determinations of the Losses of Radiation of the Cavities of Three Instruments at Different Wavelengths

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Table II Correction Factors for Seven PMO6-Type Radiometers Determined by Experimental Characterization and the Results of Comparisons with the PMO-2 Radiometer with the Sun as a Source

Equations (2)

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S = ( P s - P i ) / A ,
S = C ( P s - P i ) ,

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