Abstract

The reflectance properties of an engineering model (EM) of the Spectralon panel intended for use within an on-board calibrator (OBC) on the NASA Multiangle Imaging Spectroradiometer (MISR) instrument have been fully characterized with regard to panel uniformity and isotropy in response to three incident laser wavelengths of 442, 632.8, and 859.9 nm. A regional variation in the relative bidirectional reflectance factor (RBRF) across the surface of the EM panel, which contributes to spatial nonuniformity at the ±2% level, has been measured at all three laser wavelengths. Further, a reflectance anisotropy has been identified. The mechanism causing these departures from the ideal Lambertian surface may originate in the sanding of the Spectralon surface in the final stage of preparation. This supposition is corroborated by measurements made on a pressed polytetrafluoroethylene (PTFE) panel in which a greatly reduced anisotropy in panel RBRF is measured. The EM panel RBRF exhibits a deviation from Lambertian characteristics as an off-specular peak in the forward scattering direction. A common crossover point at an angle of reflection of ∼37° at which the BRF is constant within ±0.4% for an illumination angle range of θi = 30°–60° is observed at all three wavelengths. Two Spectralon protoflight panels that were fabricated after the EM was studied were also the subject of a uniformity study over part of the area of the Spectralon panels at the 442-nm wavelength. The analysis indicated that the panel uniformity satisfies the ±0.5% criterion, which indicates improved panel preparation. However, the off-specular peak in the forward scattering direction was essentially unchanged, with the crossover point at ∼37°.

© 1997 Optical Society of America

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References

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  1. D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
    [CrossRef]
  2. C. J. Bruegge, V. G. Duval, N. L. Chrien, D. J. Diner, “Calibration plans for the Multiangle Imaging Spectroradiometer (MISR),” Metrologia 30, 213–221 (1993).
    [CrossRef]
  3. F. E. Nicodemus, J. C. Richmond, J. J. Hsia, “Geometrical considerations and nomenclature for reflectance,” National Bureau of Standards Monograph 160 (National Bureau of Standards, U.S. Department of Commerce, Washington, D.C., 1977).
  4. B. T. McGuckin, D. A. Haner, R. T. Menzies, C. Esproles, A. M. Brothers, “Directional reflectance characterization facility and measurement methodology,” Appl. Opt. 35, 4827–4834 (1996).
    [CrossRef] [PubMed]
  5. K. E. Torrance, E. M. Sparrow, “Polarization, directional distribution and off-specular phenomena in light reflected from roughened surfaces,” J. Opt. Soc. Am. 56, 916–925 (1966).
    [CrossRef]
  6. K. E. Torrance, “Theoretical polarization of off-specular reflection peaks,” J. Heat Transfer 91, 287–290 (1969).
    [CrossRef]
  7. D. A. Haner, R. T. Menzies, “Reflectance characteristics of reference materials used in lidar hard target calibration,” Appl. Opt. 28, 857–864 (1989).
    [CrossRef] [PubMed]

1996 (1)

1993 (1)

C. J. Bruegge, V. G. Duval, N. L. Chrien, D. J. Diner, “Calibration plans for the Multiangle Imaging Spectroradiometer (MISR),” Metrologia 30, 213–221 (1993).
[CrossRef]

1989 (1)

1969 (1)

K. E. Torrance, “Theoretical polarization of off-specular reflection peaks,” J. Heat Transfer 91, 287–290 (1969).
[CrossRef]

1966 (1)

Brothers, A. M.

Bruegge, C. J.

C. J. Bruegge, V. G. Duval, N. L. Chrien, D. J. Diner, “Calibration plans for the Multiangle Imaging Spectroradiometer (MISR),” Metrologia 30, 213–221 (1993).
[CrossRef]

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Chrien, N. L.

C. J. Bruegge, V. G. Duval, N. L. Chrien, D. J. Diner, “Calibration plans for the Multiangle Imaging Spectroradiometer (MISR),” Metrologia 30, 213–221 (1993).
[CrossRef]

Deslis, T.

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Diner, D. J.

C. J. Bruegge, V. G. Duval, N. L. Chrien, D. J. Diner, “Calibration plans for the Multiangle Imaging Spectroradiometer (MISR),” Metrologia 30, 213–221 (1993).
[CrossRef]

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Duval, V. G.

C. J. Bruegge, V. G. Duval, N. L. Chrien, D. J. Diner, “Calibration plans for the Multiangle Imaging Spectroradiometer (MISR),” Metrologia 30, 213–221 (1993).
[CrossRef]

Esproles, C.

Ford, V. G.

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Haner, D. A.

Hovland, L. E.

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Hsia, J. J.

F. E. Nicodemus, J. C. Richmond, J. J. Hsia, “Geometrical considerations and nomenclature for reflectance,” National Bureau of Standards Monograph 160 (National Bureau of Standards, U.S. Department of Commerce, Washington, D.C., 1977).

McGuckin, B. T.

Menzies, R. T.

Nicodemus, F. E.

F. E. Nicodemus, J. C. Richmond, J. J. Hsia, “Geometrical considerations and nomenclature for reflectance,” National Bureau of Standards Monograph 160 (National Bureau of Standards, U.S. Department of Commerce, Washington, D.C., 1977).

Preston, D. J.

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Richmond, J. C.

F. E. Nicodemus, J. C. Richmond, J. J. Hsia, “Geometrical considerations and nomenclature for reflectance,” National Bureau of Standards Monograph 160 (National Bureau of Standards, U.S. Department of Commerce, Washington, D.C., 1977).

Shterenberg, M. J.

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Sparrow, E. M.

Torrance, K. E.

Villegas, E. B.

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

White, M. L.

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

Appl. Opt. (2)

J. Heat Transfer (1)

K. E. Torrance, “Theoretical polarization of off-specular reflection peaks,” J. Heat Transfer 91, 287–290 (1969).
[CrossRef]

J. Opt. Soc. Am. (1)

Metrologia (1)

C. J. Bruegge, V. G. Duval, N. L. Chrien, D. J. Diner, “Calibration plans for the Multiangle Imaging Spectroradiometer (MISR),” Metrologia 30, 213–221 (1993).
[CrossRef]

Other (2)

F. E. Nicodemus, J. C. Richmond, J. J. Hsia, “Geometrical considerations and nomenclature for reflectance,” National Bureau of Standards Monograph 160 (National Bureau of Standards, U.S. Department of Commerce, Washington, D.C., 1977).

D. J. Diner, C. J. Bruegge, T. Deslis, V. G. Ford, L. E. Hovland, D. J. Preston, M. J. Shterenberg, E. B. Villegas, M. L. White, “Development status of the EOS Multiangle Imaging Spectroradiometer (MISR),” in Sensor Systems for the Early Earth Observing System Platforms, W. L. Barnes, ed., Proc. SPIE1939, 94–103 (1993).
[CrossRef]

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Figures (9)

Fig. 1
Fig. 1

Optical layout used during the study of the Spectralon reflectance properties. The laser-based system can deliver a user-defined beam of chosen size and polarization and one of three wavelengths onto the Spectralon panel. The panel is held in the three-axis computer-controlled target assembly, which facilitates 360° rotation of the target and detector with ±30° tilt of the surface normal in and out of the principal plane. The symbols A, M, P, and D refer to aperture, mirror, polarizing beam splitter, and detector.

Fig. 2
Fig. 2

Details of the optical layout used in measurement of Spectralon panel RBRF with the objective of characterizing panel uniformity.

Fig. 3
Fig. 3

Diagram of the Spectralon EM panel, showing the array of 11 points for which the RBRF is recorded with the objective of characterizing panel uniformity in each of the three spectral bands. Dimensions are in millimeters.

Fig. 4
Fig. 4

Regional variation in Spectralon panel RBRF as measured at 442 nm with θi = 60° and as a function of reflected angle. The four traces following a downward slope are from positions 1–4, and those rising with a positive gradient are from positions 8–11. The lower group of three are from positions 5, 6, and 7 located along the middle of the panel. Note that %D = 0 represents the panel average.

Fig. 5
Fig. 5

Possible scheme through which the observed regional variation in the measured EM panel RBRF may have been created. The final surface preparation stage is a sanding to remove the specular reflection from the smooth surface and to reduce the thickness to a prescribed value. The three distinct tangential velocities could be the origin of the three regions; any off-level orientation of the sander could cause figuring of the surface, and the direction of the final pass could be the origin of the measured anisotropy in panel reflectance.

Fig. 6
Fig. 6

Spectralon RBRF measured at wavelength of 632.8 nm from positions 5, 6, and 7 with θi = 30°, 45°, 60°. The traces indicate the same features as those measured at 442 nm: a common RBRF is measured at the reflected angle of ∼37° and an off-specular peak. Repeatability is <0.2%.

Fig. 7
Fig. 7

An anisotropy in the Spectralon panel reflectance is revealed in this plot, showing the comparison between data files recorded with the panel oriented at θi = 45°, ϕi = 0°, 180° with an incident wavelength of 859.9 nm. Each trace corresponds to the case in which the normal to the panel surface is oriented at , +30°; □, 0°; ◇, -30° relative to the principal plane. Clearly the 0.1% criterion for panel isotropy is not satisfied, which is considered to be a further effect of the surface preparation.

Fig. 8
Fig. 8

Isotropic analysis of the pressed PTFE panel. Each trace represents the comparison of data obtained at θi = 45°, ϕi = 0°, 180° for the instances of the panel surface normal’s being at , +30°; □, 0°; ◇, -30° relative to the principal plane. Evidently, the isotropy that is at the ±1% level is much improved over the measured for the Spectralon EM panel and is further evidence that the surface preparation is the origin of the regional RBRF and anisotropy.

Fig. 9
Fig. 9

Uniformity analysis of protoflight panel 12669-5 illuminated at 442 nm. Data recorded from three positions orientated vertically across the panel again satisfies the ±0.5% criterion for uniformity. Data repeatability is at the 0.2% level.

Tables (2)

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Table 1 Archive Data File for BRF Measurement

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Table 2 Percentage Variation in Panel RBRF for Positions, Corresponding to Figures 4, 5 and 6 at Each Incident Wavelength

Equations (2)

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Xθr=111 Rθr11 for fixed λ, θi,
%D=Rθr-XθrXθr×100.

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