Abstract

Perturbations to an integrating sphere’s radiant uniformity by a protruding optical system are mapped. A sphere provides the Descent Imager–Spectral Radiometer sensor head (DISR SH), a practical platform for many of its subsystems’ calibrations, but the resulting nonuniformity threatens the goal of accurate radiometry. An apparatus with a nearly identical shape is built to measure the radiance variations. The radiance field is found to be very homogeneous (0–2% variations) over two-thirds of the sphere’s surface area, with larger excursions near the SH, away from active fields of view. This provides an accurate platform to transfer absolute calibrations.

© 2001 Optical Society of America

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References

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  1. W. A. Hovis, J. S. Knoll, “Characteristics of an internally illuminated calibration sphere.” Appl. Opt. 22, 4004–4007 (1983).
    [CrossRef]
  2. M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

1983 (1)

Buchhauser, D.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Bushroe, M.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Dafoe, L. E.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Doose, L. R.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Eibl, A.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Fellows, C.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Hovis, W. A.

Knoll, J. S.

McFarlane, E.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Pringle, M. J.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Prout, G. M.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Rizk, B.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

See, C.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Smith, P. H.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Tomasko, M. G.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Tsetsenekos, K.

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

Appl. Opt. (1)

Other (1)

M. G. Tomasko, D. Buchhauser, M. Bushroe, L. E. Dafoe, L. R. Doose, A. Eibl, C. Fellows, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See, P. H. Smith, K. Tsetsenekos are preparing a manuscript to be called “The descent imager/spectral radiometer (DISR) experiment on the Huygens entry probe of Titan.”

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Figures (7)

Fig. 1
Fig. 1

Schematic showing the relative size, orientation, and placement of the DISR SH with respect to the 50-cm-diameter integrating sphere used as the test station for performing many of the calibrations.

Fig. 2
Fig. 2

DISR SH seen from above and below, attached to the Huygens probe.

Fig. 3
Fig. 3

Diagram displaying the geometry that relates a dark or bright first-bounce region A with an arbitrary point P on the sphere’s interior wall. The various angles and line segments are labeled.

Fig. 4
Fig. 4

Photographs depicting the DSH, the apparatus used to measure the spatial dependence of radiance on location within the DISR calibration sphere. The various components of the assembly are described in the text.

Fig. 5
Fig. 5

Schematic defining the angles α and β.

Fig. 6
Fig. 6

Spatial radiance profile of the interior of the DISR calibration sphere subject to the absorbing region of the DSH. It accurately approximates the radiance field when the DSH is replaced with the actual DISR SH. Relative brightness contours, or isophotes, are marked in percentage (%) deviation relative to the front center of the integrating sphere. The locations of the actual measurements are marked with asterisks. The boundaries of the fields of view of the various DISR instruments are indicated.

Fig. 7
Fig. 7

Gray-scale image constructed of the inside of the 50-cm-diameter DISR calibration sphere derived from the spatial radiance map based on the DSH.

Tables (2)

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Table 1 DISR Sybsystems

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Table 2 Port Assignments

Equations (2)

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E=LΩ=LA cos α cos αd2=LA cos2 αd2=LA cos2 α4r2 cos2 α=LA4r2.
x=-[r2-r-d2sin2 α]1/2 cos α+r-dsin2 α, y=r2-r-d2sin2 α1/2 sin α cos β+cos αr-dsin α cos β, z=r2-r-d2sin2 α1/2 sin α sin β+cos αr-dsin α sin β, θ=cos-1z/r, ϕ=tan-1y/x,

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