Abstract

Field-based nonimaging spectroradiometers are often used in vicarious calibration experiments for airborne or spaceborne imaging spectrometers. The calibration uncertainties associated with these ground measurements contribute substantially to the overall modeling error in radiance- or reflectance-based vicarious calibration experiments. Because of limitations in the radiometric stability of compact field spectroradiometers, vicarious calibration experiments are based primarily on reflectance measurements rather than on radiance measurements. To characterize the overall uncertainty of radiance-based approaches and assess the sources of uncertainty, we carried out a full laboratory calibration. This laboratory calibration of a nonimaging spectroradiometer is based on a measurement plan targeted at achieving a ≤10% uncertainty calibration. The individual calibration steps include characterization of the signal-to-noise ratio, the noise equivalent signal, the dark current, the wavelength calibration, the spectral sampling interval, the nonlinearity, directional and positional effects, the spectral scattering, the field of view, the polarization, the size-of-source effects, and the temperature dependence of a particular instrument. The traceability of the radiance calibration is established to a secondary National Institute of Standards and Technology calibration standard by use of a 95% confidence interval and results in an uncertainty of less than ±7.1% for all spectroradiometer bands.

© 2000 Optical Society of America

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References

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  1. H. S. Chen, Remote Sensing Calibration Systems: An Introduction (Deepak, Hampton, Va., 1997), p. 238.
  2. H. R. Gordon, “In-orbit calibration strategy of ocean color sensors,” Remote Sens. Environ. 63, 265–278 (1998).
    [CrossRef]
  3. R. Green, “Spectral calibration requirement for Earth-looking imaging spectrometers in the solar-reflected spectrum,” Appl. Opt. 37, 683–690 (1998).
    [CrossRef]
  4. P. Strobl, A. Müller, D. Schläpfer, M. Schaepman, “Laboratory calibration and inflight validation of the digital airborne imaging spectrometer DAIS 7915 for the 1996 flight season,” in Algorithms for Multispectral and Hyperspectral Imagery III, A. Iverson, S. S. Shen, eds., Proc. SPIE3071, 225–236 (1997).
    [CrossRef]
  5. M. Schaepman, Calibration of a Field Spectroradiometer, Vol. 31 of Remote Sensing Series (Remote Sensing Laboratories, Department of Geography, University of Zurich, Zurich, 1998), p. 146.
  6. D. Hatchell, ed., ASD Technical Guide, 3rd. ed. (Analytical Spectral Devices, Boulder, Colo., 1999), p. 19–1.
  7. Geophysical and Environmental Research Corporation, “GER 3700: highest resolution, photodiode & photoconductor array-based spectroradiometer,” (Geophysical and Environmental Research Corporation, Millbrook, N.Y., 1993), pp. 1–2.
  8. K. Staenz, R. P. Gauthier, D. P. Witz, M. E. Schaepman, K. I. Itten, “GER 3700—a new array-based instrument for field spectroscopy in the VNIR/SWIR wavelength regions,” in Proceedings of the International Symposium on Spectral Sensing Research (Topographic Engineering Center, U.S. Army Corps of Engineers, Alexandria, Va., 1995).
  9. CR-699 ring dye laser, Coherent Laser Product Division, Palo Alto, Calif., 1977, Sec. 2, pp. 1–25.
  10. Optronic Laboratories, Inc., “Operation Manual OL450, Rev. D” (Optronic, Orlando, Fla., 1993), pp. 1–15.
  11. Optronic Laboratories, Inc., “Luminance and color temperature calibration certificate,” (Optronic, Orlando, Fla., 1996), pp. 1–9.
  12. Labsphere, “Integrating sphere theory and applications,” in Labsphere Catalog, Sphere Systems and Instrumentation (Labsphere, North Sutton, N.H., 1996), pp. 103–116.
  13. Labsphere, “Calibration data: reflectance calibration standards,” (Labsphere, North Sutton, N.H., 1995), pp. 1–4.
  14. H. J. Kostkowski, Reliable Spectroradiometry (Spectroradiometry Consulting, La Plata, Mass., 1997), p. 609.
  15. E. F. Zalewski, “Radiometry and photometry,” in Handbook of Optics, M. Bass, ed. (McGraw-Hill, New York, 1995), Vol. II, pp. 24.1–24.51.
  16. C. L. Sanders, “Accurate measurements of and corrections for non-linearities in radiometers,” J. Res. Natl. Bur. Stand. (USA) Sect. A 76, 437–439 (1972).
    [CrossRef]
  17. A. Berk, L. S. Bernstein, D. C. Robertson, “modtran: a moderate resolution model for lowtran7,” (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1989), p. 38.
  18. International Organization for Standardization, Guide to the Expression of Uncertainty in Measurement (I. O. S., Geneva, Switzerland, 1995), p. 101.
  19. B. N. Taylor, C. E. Kuyatt, “Guidelines for evaluating and expressing the uncertainty of NIST measurements results,” Natl. Inst. Stand. Technol. Tech Note 1297, 20 (1994).

1998 (2)

H. R. Gordon, “In-orbit calibration strategy of ocean color sensors,” Remote Sens. Environ. 63, 265–278 (1998).
[CrossRef]

R. Green, “Spectral calibration requirement for Earth-looking imaging spectrometers in the solar-reflected spectrum,” Appl. Opt. 37, 683–690 (1998).
[CrossRef]

1994 (1)

B. N. Taylor, C. E. Kuyatt, “Guidelines for evaluating and expressing the uncertainty of NIST measurements results,” Natl. Inst. Stand. Technol. Tech Note 1297, 20 (1994).

1972 (1)

C. L. Sanders, “Accurate measurements of and corrections for non-linearities in radiometers,” J. Res. Natl. Bur. Stand. (USA) Sect. A 76, 437–439 (1972).
[CrossRef]

Berk, A.

A. Berk, L. S. Bernstein, D. C. Robertson, “modtran: a moderate resolution model for lowtran7,” (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1989), p. 38.

Bernstein, L. S.

A. Berk, L. S. Bernstein, D. C. Robertson, “modtran: a moderate resolution model for lowtran7,” (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1989), p. 38.

Chen, H. S.

H. S. Chen, Remote Sensing Calibration Systems: An Introduction (Deepak, Hampton, Va., 1997), p. 238.

Gauthier, R. P.

K. Staenz, R. P. Gauthier, D. P. Witz, M. E. Schaepman, K. I. Itten, “GER 3700—a new array-based instrument for field spectroscopy in the VNIR/SWIR wavelength regions,” in Proceedings of the International Symposium on Spectral Sensing Research (Topographic Engineering Center, U.S. Army Corps of Engineers, Alexandria, Va., 1995).

Gordon, H. R.

H. R. Gordon, “In-orbit calibration strategy of ocean color sensors,” Remote Sens. Environ. 63, 265–278 (1998).
[CrossRef]

Green, R.

Itten, K. I.

K. Staenz, R. P. Gauthier, D. P. Witz, M. E. Schaepman, K. I. Itten, “GER 3700—a new array-based instrument for field spectroscopy in the VNIR/SWIR wavelength regions,” in Proceedings of the International Symposium on Spectral Sensing Research (Topographic Engineering Center, U.S. Army Corps of Engineers, Alexandria, Va., 1995).

Kostkowski, H. J.

H. J. Kostkowski, Reliable Spectroradiometry (Spectroradiometry Consulting, La Plata, Mass., 1997), p. 609.

Kuyatt, C. E.

B. N. Taylor, C. E. Kuyatt, “Guidelines for evaluating and expressing the uncertainty of NIST measurements results,” Natl. Inst. Stand. Technol. Tech Note 1297, 20 (1994).

Müller, A.

P. Strobl, A. Müller, D. Schläpfer, M. Schaepman, “Laboratory calibration and inflight validation of the digital airborne imaging spectrometer DAIS 7915 for the 1996 flight season,” in Algorithms for Multispectral and Hyperspectral Imagery III, A. Iverson, S. S. Shen, eds., Proc. SPIE3071, 225–236 (1997).
[CrossRef]

Robertson, D. C.

A. Berk, L. S. Bernstein, D. C. Robertson, “modtran: a moderate resolution model for lowtran7,” (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1989), p. 38.

Sanders, C. L.

C. L. Sanders, “Accurate measurements of and corrections for non-linearities in radiometers,” J. Res. Natl. Bur. Stand. (USA) Sect. A 76, 437–439 (1972).
[CrossRef]

Schaepman, M.

P. Strobl, A. Müller, D. Schläpfer, M. Schaepman, “Laboratory calibration and inflight validation of the digital airborne imaging spectrometer DAIS 7915 for the 1996 flight season,” in Algorithms for Multispectral and Hyperspectral Imagery III, A. Iverson, S. S. Shen, eds., Proc. SPIE3071, 225–236 (1997).
[CrossRef]

M. Schaepman, Calibration of a Field Spectroradiometer, Vol. 31 of Remote Sensing Series (Remote Sensing Laboratories, Department of Geography, University of Zurich, Zurich, 1998), p. 146.

Schaepman, M. E.

K. Staenz, R. P. Gauthier, D. P. Witz, M. E. Schaepman, K. I. Itten, “GER 3700—a new array-based instrument for field spectroscopy in the VNIR/SWIR wavelength regions,” in Proceedings of the International Symposium on Spectral Sensing Research (Topographic Engineering Center, U.S. Army Corps of Engineers, Alexandria, Va., 1995).

Schläpfer, D.

P. Strobl, A. Müller, D. Schläpfer, M. Schaepman, “Laboratory calibration and inflight validation of the digital airborne imaging spectrometer DAIS 7915 for the 1996 flight season,” in Algorithms for Multispectral and Hyperspectral Imagery III, A. Iverson, S. S. Shen, eds., Proc. SPIE3071, 225–236 (1997).
[CrossRef]

Staenz, K.

K. Staenz, R. P. Gauthier, D. P. Witz, M. E. Schaepman, K. I. Itten, “GER 3700—a new array-based instrument for field spectroscopy in the VNIR/SWIR wavelength regions,” in Proceedings of the International Symposium on Spectral Sensing Research (Topographic Engineering Center, U.S. Army Corps of Engineers, Alexandria, Va., 1995).

Strobl, P.

P. Strobl, A. Müller, D. Schläpfer, M. Schaepman, “Laboratory calibration and inflight validation of the digital airborne imaging spectrometer DAIS 7915 for the 1996 flight season,” in Algorithms for Multispectral and Hyperspectral Imagery III, A. Iverson, S. S. Shen, eds., Proc. SPIE3071, 225–236 (1997).
[CrossRef]

Taylor, B. N.

B. N. Taylor, C. E. Kuyatt, “Guidelines for evaluating and expressing the uncertainty of NIST measurements results,” Natl. Inst. Stand. Technol. Tech Note 1297, 20 (1994).

Witz, D. P.

K. Staenz, R. P. Gauthier, D. P. Witz, M. E. Schaepman, K. I. Itten, “GER 3700—a new array-based instrument for field spectroscopy in the VNIR/SWIR wavelength regions,” in Proceedings of the International Symposium on Spectral Sensing Research (Topographic Engineering Center, U.S. Army Corps of Engineers, Alexandria, Va., 1995).

Zalewski, E. F.

E. F. Zalewski, “Radiometry and photometry,” in Handbook of Optics, M. Bass, ed. (McGraw-Hill, New York, 1995), Vol. II, pp. 24.1–24.51.

Appl. Opt. (1)

J. Res. Natl. Bur. Stand. (USA) Sect. A (1)

C. L. Sanders, “Accurate measurements of and corrections for non-linearities in radiometers,” J. Res. Natl. Bur. Stand. (USA) Sect. A 76, 437–439 (1972).
[CrossRef]

Natl. Inst. Stand. Technol. Tech Note (1)

B. N. Taylor, C. E. Kuyatt, “Guidelines for evaluating and expressing the uncertainty of NIST measurements results,” Natl. Inst. Stand. Technol. Tech Note 1297, 20 (1994).

Remote Sens. Environ. (1)

H. R. Gordon, “In-orbit calibration strategy of ocean color sensors,” Remote Sens. Environ. 63, 265–278 (1998).
[CrossRef]

Other (15)

H. S. Chen, Remote Sensing Calibration Systems: An Introduction (Deepak, Hampton, Va., 1997), p. 238.

A. Berk, L. S. Bernstein, D. C. Robertson, “modtran: a moderate resolution model for lowtran7,” (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1989), p. 38.

International Organization for Standardization, Guide to the Expression of Uncertainty in Measurement (I. O. S., Geneva, Switzerland, 1995), p. 101.

P. Strobl, A. Müller, D. Schläpfer, M. Schaepman, “Laboratory calibration and inflight validation of the digital airborne imaging spectrometer DAIS 7915 for the 1996 flight season,” in Algorithms for Multispectral and Hyperspectral Imagery III, A. Iverson, S. S. Shen, eds., Proc. SPIE3071, 225–236 (1997).
[CrossRef]

M. Schaepman, Calibration of a Field Spectroradiometer, Vol. 31 of Remote Sensing Series (Remote Sensing Laboratories, Department of Geography, University of Zurich, Zurich, 1998), p. 146.

D. Hatchell, ed., ASD Technical Guide, 3rd. ed. (Analytical Spectral Devices, Boulder, Colo., 1999), p. 19–1.

Geophysical and Environmental Research Corporation, “GER 3700: highest resolution, photodiode & photoconductor array-based spectroradiometer,” (Geophysical and Environmental Research Corporation, Millbrook, N.Y., 1993), pp. 1–2.

K. Staenz, R. P. Gauthier, D. P. Witz, M. E. Schaepman, K. I. Itten, “GER 3700—a new array-based instrument for field spectroscopy in the VNIR/SWIR wavelength regions,” in Proceedings of the International Symposium on Spectral Sensing Research (Topographic Engineering Center, U.S. Army Corps of Engineers, Alexandria, Va., 1995).

CR-699 ring dye laser, Coherent Laser Product Division, Palo Alto, Calif., 1977, Sec. 2, pp. 1–25.

Optronic Laboratories, Inc., “Operation Manual OL450, Rev. D” (Optronic, Orlando, Fla., 1993), pp. 1–15.

Optronic Laboratories, Inc., “Luminance and color temperature calibration certificate,” (Optronic, Orlando, Fla., 1996), pp. 1–9.

Labsphere, “Integrating sphere theory and applications,” in Labsphere Catalog, Sphere Systems and Instrumentation (Labsphere, North Sutton, N.H., 1996), pp. 103–116.

Labsphere, “Calibration data: reflectance calibration standards,” (Labsphere, North Sutton, N.H., 1995), pp. 1–4.

H. J. Kostkowski, Reliable Spectroradiometry (Spectroradiometry Consulting, La Plata, Mass., 1997), p. 609.

E. F. Zalewski, “Radiometry and photometry,” in Handbook of Optics, M. Bass, ed. (McGraw-Hill, New York, 1995), Vol. II, pp. 24.1–24.51.

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Figures (13)

Fig. 1
Fig. 1

Three types of measurement setup for the characterization process. The place holder is a black anodized aluminum holder that mechanically and optically fits the spectroradiometer tightly to the sphere’s exit port. Type 2 measurements were performed on the optical table of the tunable dye laser. Type 3 measurements were performed to measure the FOV. The illuminating source is the Sun (Type 3b) or tungsten halogen lamps (Type 3a).

Fig. 2
Fig. 2

SNR determination with a 2200-fL luminance setting corresponding to the upper radiance values expected in field measurements (e.g., Spectralon reflectance level as depicted in Fig. 8 below) and the measured standard deviation [see Eq. (1)].

Fig. 3
Fig. 3

NES and NER measurements (NER is derived from the final calibration coefficients and applied to NES).

Fig. 4
Fig. 4

Dark current (bottom) and plot of the lowest measured signal (top) during characterization. The 25-fL setting is not used as calibration reference because it may not be traceable.

Fig. 5
Fig. 5

Response of the spectroradiometer to the laser at 593.6 nm. The peak signal is greater than 5,000 DN, compared with the background signal of ∼10 DN (i.e., SNR of 500). There is minor asymmetry in the response of the spectroradiometer to the laser line that is due to the presence of many intermediate optical elements in the optical path of the laser.

Fig. 6
Fig. 6

Normalized measurements and the Gaussian fit to determine the FWHM for one spectrometer band.

Fig. 7
Fig. 7

Original (solid lines) and calibrated (dashed curves) FWHM plotted against the wavelength range of the radiometer.

Fig. 8
Fig. 8

Comparison of original (NIST) upper (2200-fL) and lower (200-fL) calibration radiances. The upper solid curve is a modtran simulation of a Spectralon panel; the lower solid curve is a modtran simulation of a 1% reflecting target.

Fig. 9
Fig. 9

Superpositions measured during the linearity test in the calibration range from 200 to 2200 fL.

Fig. 10
Fig. 10

Polarization sensitivity D(M) scaled on the left axis from 1.5% to 6.5% in the observed region. The polarization-dependent loss (scaled on the right axis) does not exceed 0.5% for this measurement setup. D(M) shows that the radiometer is polarization sensitive and that under optimal circumstances the polarization-dependent loss is less than 0.4%.

Fig. 11
Fig. 11

Three temperature-dependent models of detector PbS1.

Fig. 12
Fig. 12

Calibration gain and calibration offset for all 704 GER3700 spectroradiometer bands.

Fig. 13
Fig. 13

Reflectance-calibrated data displaying the uncertainty change at 2200 nm of the NIST-calibrated reflectance spectrum.

Tables (5)

Tables Icon

Table 1 Manufacturer Specifications of the GER3700 Spectroradiometer

Tables Icon

Table 2 Measurement Plan and Expected Errors for the Laboratory Calibration

Tables Icon

Table 3 Corresponding NSR of SNR Measurements

Tables Icon

Table 4 Uncertainties for a ≤10% Laboratory Calibration of the GER3700 Spectroradiometer at 200 fL

Tables Icon

Table 5 Expanded Uncertainty of the GER3700 Spectroradiometer Laboratory Calibration

Equations (29)

Equations on this page are rendered with MathJax. Learn more.

SNR=SN=RDN, total-RDN, darkσ2RDN, total+σ2RDN, dark1/2,
NES=σ2RDN, total+σ2RDN, dark1/2,  NER=NES Cgain,
Rdark=1ni=1n R0=R¯0,
RDN=k0+k1 exp-λGER-λlaserk32,
Kab=ia+bia+ib,
ia=RLa,
ia+b=KabRLa+b.
θf=2α=2 arctanh-k0hk1,
S=12s0s0 cos 2ϕs0 sin 2ϕ0=12 s01cos 2ϕsin 2ϕ0,
DM=m012+m0221/2m00,
PDLM=10 logm00+m012+m022+m0321/2m00-m012+m022+m0321/2.
R=1/2 L01+s1 cos 2ϕ+s2 sin 2ϕRΔλΔΘ,
R45s1-R0s2=R0-R45,  R45s1+R90s2=R45-R90,
S=1/2 L01+s1 cos 2ϕ+s3 sin 2ϕ,
s3=R0-R45R0+R45.
m=1m01m02m03,
R=1/2 L01+m01 cos 2ϕ+m02 sin 2ϕRΔλΔΘ
R0R45=1+m011+m02,
R45R90=1+m021-m01,
m03=R45-R0R0+R45.
Pcorr=1+s1Sm01+s2Sm02+s3Sm031+s1m01+s2m02+s3m03,
RDN,TPbS=k0+k1 exp-k2k3,
uc2y=i=1Nfxi2u2xi+2 i=1N-1j=i+1Nfxifxj uxi, xj,
U=kucy,
Y=y±U,
ucy=ymax-ymin/23,
νi=n-m,
Up=kpucy,
Lλ=Cgain,λRDN+Coffset,λ,

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