Immersion Factor of In-Water Radiance Sensors: Assessment for a Class of Radiometers

Giuseppe Zibordi Inland and Marine Waters Unit, Joint Research Centre of the European Union, Ispra, Italy

Search for other papers by Giuseppe Zibordi in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The spectral immersion factor of in-water radiance sensors If quantifies the effects of changes in the sensor's response when operated in water versus in air. The values of If are currently computed with a relationship derived from a basic sensor model, which only requires knowledge of the refractive indices of the water and the material constituting the sensor's optical window in contact herewith. Uncertainties in the computation of If are investigated in the 400–700-nm spectral range for a specific class of widely used multispectral radiometers. The analysis is made by comparing If values from the theoretical relationship currently in use with (i) If from a new relationship based on an extended sensor model accounting for the actual solid-angle field of view and the reflectance and transmittance of the external and internal optical components, and (ii) experimental If determined with sample radiometers having diverse optical windows made of materials with different refractive indices. Results highlight that the relationship derived from the basic sensor model introduces a 0.4% negative bias when applied to the considered class of radiometers having a fused silica optical window, a 13° in-air half-angle field of view, and an estimated detector reflectance of 0.15. Reference values of If for the specific class of radiometers, determined with the newly proposed relationship, are presented, and their dependence on seawater temperature and salinity is discussed.

Corresponding author address: Dr. Giuseppe Zibordi, Joint Research Centre, Institute for Environment and Sustainability, Inland and Marine Waters Unit TP272, 21020 Ispra, Italy. Email: giuseppe.zibordi@jrc.it

Abstract

The spectral immersion factor of in-water radiance sensors If quantifies the effects of changes in the sensor's response when operated in water versus in air. The values of If are currently computed with a relationship derived from a basic sensor model, which only requires knowledge of the refractive indices of the water and the material constituting the sensor's optical window in contact herewith. Uncertainties in the computation of If are investigated in the 400–700-nm spectral range for a specific class of widely used multispectral radiometers. The analysis is made by comparing If values from the theoretical relationship currently in use with (i) If from a new relationship based on an extended sensor model accounting for the actual solid-angle field of view and the reflectance and transmittance of the external and internal optical components, and (ii) experimental If determined with sample radiometers having diverse optical windows made of materials with different refractive indices. Results highlight that the relationship derived from the basic sensor model introduces a 0.4% negative bias when applied to the considered class of radiometers having a fused silica optical window, a 13° in-air half-angle field of view, and an estimated detector reflectance of 0.15. Reference values of If for the specific class of radiometers, determined with the newly proposed relationship, are presented, and their dependence on seawater temperature and salinity is discussed.

Corresponding author address: Dr. Giuseppe Zibordi, Joint Research Centre, Institute for Environment and Sustainability, Inland and Marine Waters Unit TP272, 21020 Ispra, Italy. Email: giuseppe.zibordi@jrc.it

Save
  • Aas, E., 1969: On submarine irradiance measurements. Institute of Physical Oceanography, University of Copenhagen, 23 pp. plus tables and figures.

  • Atkins, W. R. G., and Poole H. H. , 1933: The photo-electric measurement of the penetration of light of various wave lengths into the sea and the physiological bearing of results. Philos. Trans. Roy. Soc. London, 222B , 129164.

    • Search Google Scholar
    • Export Citation
  • Austin, R. W., 1976: Air–water radiance calibration factor. Scripps Institution of Oceanography Tech. Memo. ML-76-004T, 8 pp.

  • Austin, R. W., and Halikas G. , 1976: The index of refraction of seawater. Scripps Institution of Oceanography Ref. Rep. 76-1, 64 pp.

    • Crossref
    • Export Citation
  • Austin, R. W., and Petzold T. J. , 1982: Air–water radiance factor—Gershun tube. Scripps Institution of Oceanography Tech. Memo. DL-82-005T, 20 pp.

  • Berger, F., 1958: Über die Ursache des “Oberflächeneffekts” bei Lichtmessungen unter Wasser. Wetter Leben, 10 , 164170.

  • Berger, F., 1961: Über den “Taucheffekt” bei der Lichtmessung über and unter Wasser. Arch. Meteor. Wien, 11B , 224240.

  • Hooker, S. B., and Zibordi G. , 2005: Advanced methods for characterizing the immersion factor of irradiance sensors. J. Atmos. Oceanic Technol, 22 , 757770.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hooker, S. B., McLean S. , Small M. , Lazin G. , Zibordi G. , and Brown J. , 2002: The seventh SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-7), March 1999. NASA Goddard Space Flight Center Tech. Memo. 1999-206892, Vol. 17, 69 pp.

  • Johnson, B. C., and Coauthors, 1999: The fifth SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-5), July 1996. NASA Goddard Space Flight Center Tech. Memo. 1999-206892, Vol. 7, 75 pp.

  • Malitson, I. H., 1965: Interspecimen comparison of the refractive index of fused silica. J. Opt. Soc. Amer, 55 , 12051209.

  • Morel, A., 1974: Optical properties of pure water and pure sea water. Optical Aspects of Oceanography, N. G. Jerlov and E. Steemann Nielsen, Eds., Academic Press, 1–24.

    • Search Google Scholar
    • Export Citation
  • Mueller, J. L., and Austin R. W. , 1995: Ocean optics protocols for SeaWiFS validation, revision 1. NASA Goddard Space Flight Center Tech. Memo. 104566, Vol. 25, 67 pp.

  • Mueller, J. L., and Austin R. W. , 2003: Characterization of oceanographic and atmospheric radiometers. NASA Goddard Space Flight Center Tech. Memo. 211621/Rev4, Vol. II, 17–33.

  • Mueller, J. L., Johnson B. C. , Cromer C. L. , Hooker S. B. , McLean J. T. , and Biggar S. F. , 1996: The third SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-3), September 1994. NASA Goddard Space Flight Center Tech. Memo. 104566, Vol. 34, 78 pp.

  • Oriel, 2000: Optics and filters. Properties of Optical Materials, Oriel Corporation, 12.1–12.6.

  • Petzold, T. J., and Austin R. W. , 1988: Chracterization of MER-1032. Visibility Laboratory of the Scripps Institution of Oceanography, University of California, San Diego, Tech. Memo. EN-001-88T, 56 pp.

  • Pope, R. M., and Fry E. S. , 1997: Absorption spectrum (380-700 nm) of pure water. II. Integrating cavity measurements. Appl. Opt, 36 , 87108723.

  • Press, W. H., Tuekolsky S. A. , Vettering W. T. , and Flannery B. P. , 1992: Numerical Recipes in C: The Art of Scientific Computing. Cambridge University Press, 994 pp.

    • Search Google Scholar
    • Export Citation
  • Smith, R. C., 1969: An underwater spectral irradiance collector. J. Mar. Res, 27 , 341351.

  • Westlake, D. F., 1965: Some problems in the measurement of radiation under water: A review. Photochem. Photobiol, 4 , 849868.

  • Zibordi, G., D'Alimonte D. , van der Linde D. , Berthon J-F. , Hooker S. B. , Mueller J. L. , Lazin G. , and McLean S. , 2002: The eighth SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-8), September–December 2001. NASA Goddard Space Flight Center Tech. Memo. 2002-206892, Vol. 21, 39 pp.

  • Zibordi, G., D'Alimonte D. , and Berthon J-F. , 2004a: An evaluation of depth resolution requirements for optical profiling in coastal waters. J. Atmos. Oceanic Technol, 21 , 10591073.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zibordi, G., Hooker S. , Mueller J. , and Lazin G. , 2004b: Characterization of the immersion factor for a series of in-water optical radiometers. J. Atmos. Oceanic Technol, 21 , 501514.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zissis, G. J., 1993: Radiometry. The Infrared Handbook, W. L. Wolfe and G. J. Zissis, Eds., Environment Research Institute of Michigan, 1–66.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 624 147 8
PDF Downloads 310 102 7