Abstract

The interferometer for emission and solar absorption (INTESA) is an infrared spectrometer designed to study radiative transfer in the troposphere and lower stratosphere from a NASA ER-2 aircraft. The Fourier-transform spectrometer (FTS) operates from 0.7 to 50 µm with a resolution of 0.7 cm-1. The FTS observes atmospheric thermal emission from multiple angles above and below the aircraft. A heliostat permits measurement of solar absorption spectra. INTESA’s calibration system includes three blackbodies to permit in-flight assessment of radiometric error. Results suggest that the in-flight radiometric accuracy is ∼0.5 K in the mid-infrared.

© 2001 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
    [CrossRef]
  2. D. Cousins, W. L. Smith, “National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I),” in Application of Lidar to Current Atmospheric Topics, A. J. Sedlacek, Fischer, eds., Proc SPIE3127, 323–331 (1997).
  3. D. G. Johnson, K. W. Jucks, W. A. Traub, K. V. Chance, “Smithsonian stratospheric far-infrared spectrometer and data reduction system,” J. Geophys. Res. 100, 3091–3106 (1995).
    [CrossRef]
  4. G. C. Toon, “The JPL MkIV interferometer,” Opt. Photon. News 2, 19–21 (1991).
    [CrossRef]
  5. L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
    [CrossRef]
  6. A. Sinha, J. E. Harries, “The Earth’s clear-sky radiation budget and water vapor absorption in the far infrared,” J. Clim. 10, 1601–1614 (1997).
    [CrossRef]
  7. H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).
  8. D. W. Keith, J. G. Anderson, “Accurate spectrally resolved infrared radiance observation from space: implications for the detection of decade-to-century-scale climatic change,” J. Clim. 14, 979–990 (2001).
    [CrossRef]
  9. R. J. Chandos, R. E. Chandos, “Radiometric properties of isothermal diffuse wall cavity sources,” Appl. Opt. 13, 2142–2151 (1974).
    [CrossRef] [PubMed]
  10. T. Hawat, C. Camry-Peyret, R. Torguet, “Suntracker for atmospheric remote sensing,” Opt. Eng. 37, 1633–1642 (1998).
    [CrossRef]
  11. H. E. Revercomb, H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith, L. A. Sromovsky, “Radiometric calibration of IR Fourier-transform spectrometers: solution to a problem with the High-Resolution Interferometer Sounder,” Appl. Opt. 27, 3210–3218 (1988).
    [CrossRef] [PubMed]
  12. H. Hu, L. L. Strow, D. W. Keith, J. G. Anderson, “Validation of radiative transfer for atmospheric temperature sensing,” in Tenth Conference on Atmospheric Radiation (American Meteorological Society, Boston, Mass., 1999). Other representative data and analysis can be found at http://www.arp.harvard.edu/sci/rad .

2001 (1)

D. W. Keith, J. G. Anderson, “Accurate spectrally resolved infrared radiance observation from space: implications for the detection of decade-to-century-scale climatic change,” J. Clim. 14, 979–990 (2001).
[CrossRef]

1998 (2)

T. Hawat, C. Camry-Peyret, R. Torguet, “Suntracker for atmospheric remote sensing,” Opt. Eng. 37, 1633–1642 (1998).
[CrossRef]

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

1997 (1)

A. Sinha, J. E. Harries, “The Earth’s clear-sky radiation budget and water vapor absorption in the far infrared,” J. Clim. 10, 1601–1614 (1997).
[CrossRef]

1995 (1)

D. G. Johnson, K. W. Jucks, W. A. Traub, K. V. Chance, “Smithsonian stratospheric far-infrared spectrometer and data reduction system,” J. Geophys. Res. 100, 3091–3106 (1995).
[CrossRef]

1991 (1)

G. C. Toon, “The JPL MkIV interferometer,” Opt. Photon. News 2, 19–21 (1991).
[CrossRef]

1988 (2)

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

H. E. Revercomb, H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith, L. A. Sromovsky, “Radiometric calibration of IR Fourier-transform spectrometers: solution to a problem with the High-Resolution Interferometer Sounder,” Appl. Opt. 27, 3210–3218 (1988).
[CrossRef] [PubMed]

1974 (1)

Anderson, J.

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

Anderson, J. G.

D. W. Keith, J. G. Anderson, “Accurate spectrally resolved infrared radiance observation from space: implications for the detection of decade-to-century-scale climatic change,” J. Clim. 14, 979–990 (2001).
[CrossRef]

Buijs, H.

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

H. E. Revercomb, H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith, L. A. Sromovsky, “Radiometric calibration of IR Fourier-transform spectrometers: solution to a problem with the High-Resolution Interferometer Sounder,” Appl. Opt. 27, 3210–3218 (1988).
[CrossRef] [PubMed]

Camry-Peyret, C.

T. Hawat, C. Camry-Peyret, R. Torguet, “Suntracker for atmospheric remote sensing,” Opt. Eng. 37, 1633–1642 (1998).
[CrossRef]

Chance, K. V.

D. G. Johnson, K. W. Jucks, W. A. Traub, K. V. Chance, “Smithsonian stratospheric far-infrared spectrometer and data reduction system,” J. Geophys. Res. 100, 3091–3106 (1995).
[CrossRef]

Chandos, R. E.

Chandos, R. J.

Cousins, D.

D. Cousins, W. L. Smith, “National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I),” in Application of Lidar to Current Atmospheric Topics, A. J. Sedlacek, Fischer, eds., Proc SPIE3127, 323–331 (1997).

Dykema, J.

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

Hannon, S. E.

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

Harries, J. E.

A. Sinha, J. E. Harries, “The Earth’s clear-sky radiation budget and water vapor absorption in the far infrared,” J. Clim. 10, 1601–1614 (1997).
[CrossRef]

Hawat, T.

T. Hawat, C. Camry-Peyret, R. Torguet, “Suntracker for atmospheric remote sensing,” Opt. Eng. 37, 1633–1642 (1998).
[CrossRef]

Howell, H. B.

Hu, H.

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

Johnson, D. G.

D. G. Johnson, K. W. Jucks, W. A. Traub, K. V. Chance, “Smithsonian stratospheric far-infrared spectrometer and data reduction system,” J. Geophys. Res. 100, 3091–3106 (1995).
[CrossRef]

Jucks, K. W.

D. G. Johnson, K. W. Jucks, W. A. Traub, K. V. Chance, “Smithsonian stratospheric far-infrared spectrometer and data reduction system,” J. Geophys. Res. 100, 3091–3106 (1995).
[CrossRef]

Keith, D.

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

Keith, D. W.

D. W. Keith, J. G. Anderson, “Accurate spectrally resolved infrared radiance observation from space: implications for the detection of decade-to-century-scale climatic change,” J. Clim. 14, 979–990 (2001).
[CrossRef]

Knuteson, R. O.

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

LaPorte, D. D.

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

H. E. Revercomb, H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith, L. A. Sromovsky, “Radiometric calibration of IR Fourier-transform spectrometers: solution to a problem with the High-Resolution Interferometer Sounder,” Appl. Opt. 27, 3210–3218 (1988).
[CrossRef] [PubMed]

Lapson, L.

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

McMillan, W. W.

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

Murcray, D. G.

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

Murcray, F. J.

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

Revercomb, H. E.

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

H. E. Revercomb, H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith, L. A. Sromovsky, “Radiometric calibration of IR Fourier-transform spectrometers: solution to a problem with the High-Resolution Interferometer Sounder,” Appl. Opt. 27, 3210–3218 (1988).
[CrossRef] [PubMed]

Sinha, A.

A. Sinha, J. E. Harries, “The Earth’s clear-sky radiation budget and water vapor absorption in the far infrared,” J. Clim. 10, 1601–1614 (1997).
[CrossRef]

Smith, W. L.

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

H. E. Revercomb, H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith, L. A. Sromovsky, “Radiometric calibration of IR Fourier-transform spectrometers: solution to a problem with the High-Resolution Interferometer Sounder,” Appl. Opt. 27, 3210–3218 (1988).
[CrossRef] [PubMed]

D. Cousins, W. L. Smith, “National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I),” in Application of Lidar to Current Atmospheric Topics, A. J. Sedlacek, Fischer, eds., Proc SPIE3127, 323–331 (1997).

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

Sromovsky, L. A.

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

H. E. Revercomb, H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith, L. A. Sromovsky, “Radiometric calibration of IR Fourier-transform spectrometers: solution to a problem with the High-Resolution Interferometer Sounder,” Appl. Opt. 27, 3210–3218 (1988).
[CrossRef] [PubMed]

Strow, L. L.

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

Tobin, D. C.

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

Toon, G. C.

G. C. Toon, “The JPL MkIV interferometer,” Opt. Photon. News 2, 19–21 (1991).
[CrossRef]

Torguet, R.

T. Hawat, C. Camry-Peyret, R. Torguet, “Suntracker for atmospheric remote sensing,” Opt. Eng. 37, 1633–1642 (1998).
[CrossRef]

Traub, W. A.

D. G. Johnson, K. W. Jucks, W. A. Traub, K. V. Chance, “Smithsonian stratospheric far-infrared spectrometer and data reduction system,” J. Geophys. Res. 100, 3091–3106 (1995).
[CrossRef]

Appl. Opt. (2)

J. Clim. (2)

A. Sinha, J. E. Harries, “The Earth’s clear-sky radiation budget and water vapor absorption in the far infrared,” J. Clim. 10, 1601–1614 (1997).
[CrossRef]

D. W. Keith, J. G. Anderson, “Accurate spectrally resolved infrared radiance observation from space: implications for the detection of decade-to-century-scale climatic change,” J. Clim. 14, 979–990 (2001).
[CrossRef]

J. Geophys. Res. (1)

D. G. Johnson, K. W. Jucks, W. A. Traub, K. V. Chance, “Smithsonian stratospheric far-infrared spectrometer and data reduction system,” J. Geophys. Res. 100, 3091–3106 (1995).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer (1)

L. L. Strow, D. C. Tobin, W. W. McMillan, S. E. Hannon, W. L. Smith, H. E. Revercomb, R. O. Knuteson, “Impact of a new water vapor continuum and line shape model on observed high resolution infrared radiances,” J. Quant. Spectrosc. Radiat. Transfer 59, 303–317 (1998).
[CrossRef]

Mikrochim. Acta (1)

H. E. Revercomb, D. D. LaPorte, W. L. Smith, H. Buijs, D. G. Murcray, F. J. Murcray, L. A. Sromovsky, “High-altitude aircraft measurements of upwelling IR radiance: prelude to FTIR from geosynchronous satellite,” Mikrochim. Acta 2, 439–444 (1988).
[CrossRef]

Opt. Eng. (1)

T. Hawat, C. Camry-Peyret, R. Torguet, “Suntracker for atmospheric remote sensing,” Opt. Eng. 37, 1633–1642 (1998).
[CrossRef]

Opt. Photon. News (1)

G. C. Toon, “The JPL MkIV interferometer,” Opt. Photon. News 2, 19–21 (1991).
[CrossRef]

Other (3)

D. Cousins, W. L. Smith, “National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I),” in Application of Lidar to Current Atmospheric Topics, A. J. Sedlacek, Fischer, eds., Proc SPIE3127, 323–331 (1997).

H. Hu, L. L. Strow, D. W. Keith, J. G. Anderson, “Validation of radiative transfer for atmospheric temperature sensing,” in Tenth Conference on Atmospheric Radiation (American Meteorological Society, Boston, Mass., 1999). Other representative data and analysis can be found at http://www.arp.harvard.edu/sci/rad .

H. Hu, J. Dykema, D. Keith, L. Lapson, J. Anderson, R. O. Knuteson, W. L. Smith, “Intercomparison of atmospheric radiance measurements by two Fourier transform spectrometers flown on the NASA ER-2,” in IRS2000: Current Problems in Atmospheric Radiation, W. L. Smith, Y. M. Timofeyev, eds. (Deepak, Hampton, Va., 2001).

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (8)

Fig. 1
Fig. 1

Schematic of the full optical system. All transmissive optics and moving mirrors are indicated. Numerous flat folding mirrors are omitted, as are the focusing mirrors for the infrared detectors (shown as optic 4 in Fig. 2). A more detailed layout of the fore optics and interferometer is found in Fig. 2. The schematic substantially distorts the system geometry; for example, the three cryogenically cooled detectors (InSb, 15-µm HgCdTe, and 25-µm HgCdTe) are located in the same detector Dewar.

Fig. 2
Fig. 2

Schematic of the optical system for a single cryogenic detector. All folding mirrors, except those in the interferometer core, are omitted. Optics 1–4 are illustrated as thin lenses but all are, in fact, mirrors with spherical or parabolic surfaces. The schematic shows the layout of the Bomem midband interferometer projected onto a single plane. In fact, the beam exiting the interferometer is translated into the page one beam diameter so that optic 4 and the detector are on a different plane from optics 1–3. FL, focal length.

Fig. 3
Fig. 3

Mechanical layout of INTESA showing components on both sides of the optical plate. The illustration is derived from computer-aided design drawings, so the geometry is exact—note the 10-cm-scale key.

Fig. 4
Fig. 4

Assessment of radiometric consistency. All three panels show the same flight and laboratory data, averaged over the 800–1000-cm-1 spectral window. The x axis shows the mean radiance in this spectral window of the Planck function evaluated at the measured blackbody temperature, except for the cryogenic blackbody and the zenith view for which zero radiance is assumed. (At cruise altitude the zenith view is effectively a deep-space view in the window region.) The top panel plots the raw signal. The points are labeled with the corresponding blackbody or scene temperature. The left-hand y axis corresponds to the upper curve (flight data); the right-hand y axis corresponds to the lower curve (laboratory data). The signals are phase corrected by use of the complex phase angle of the warmest blackbody to correct all others; the value plotted is the real part of the results with the minimum-to-maximum range of the signal normalized to unity. The middle panel shows the residuals from a linear fit to the data, equivalent to the residual radiance error at each point normalized to the full-scaled radiance. The lower panel shows the residuals in equivalent temperature units. The zero radiance points are omitted because their equivalent temperature error is infinite.

Fig. 5
Fig. 5

Comparison of radiance measurements from INTESA and NAST-I. The spectra are nadir views over the clear-sky ocean. They were acquired from an ER-2 flight out of Wallops Flight Facility, 23 August 1999, at an altitude of 50 hPa, at 40 °N 73 °W. The plots show two different frequency ranges. In the upper panel of each plot the INTESA data are shifted upwards by 10 K, which puts them above the NAST-I data. The differences (INTESA - NAST-I) are shown on the lower panel of each plot. This figure is abstracted from a more detailed account of the INTESA–NAST-I intercomparison.7

Fig. 6
Fig. 6

Cloud-free nadir spectra from cruise altitude over the Pacific Ocean. The data are from 17 °N 121 °W at a 21-km altitude, except the DTGS data that are an average for the entire flight. The key at the bottom indicates which of four detectors is plotted, where LW and MB are the 25- and 15-µm cutoff HgCdTe detectors.

Fig. 7
Fig. 7

Measured noise-equivalent spectral radiance (NESR) of the infrared detectors. NESR is in units of W cm-2 sr-1 (cm-1)-1 at a spectral point spacing of 0.5 cm-1 (unapodized resolution of ∼0.7 cm-1) with 1-s total interferogram acquisition time. Data are from the laboratory, and flight results differ by no more than 30%, except for the DTGS. Typical flight spectra are recorded with 8-s integration giving 2.8 times lower NESR.

Fig. 8
Fig. 8

Solar spectra in the upper panel shows solar absorption viewed through the heliostat with the InSb detector from an altitude of 9.9 km with a solar zenith angle of 56°. The signal is shown on a log scale to demonstrate the SNR. Note that the broad absorption maximum in the 2300–2400-cm-1 region is bounded at the high-frequency end by the 4.3-µm CO2 band edge. CH4 is visible between 2900 and 3100 cm-1. The lower panel shows the A band of atmospheric O2 at 0.76 µm observed at sea level with the PMT. The instrument observed the sky through a diffuse reflecting surface (white paper).

Tables (3)

Tables Icon

Table 1 Summary of Detectors

Tables Icon

Table 2 Summary of FTS Optical Properties

Tables Icon

Table 3 Detector Specifications

Metrics