Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [TP-2 SPECTRAL SIGNATURES]

Document type:: Multivolume work

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Chapter

Title:: EFFECTS OF SPECTRAL SHIFTS ON SENSOR RESPONSE. P. M. Teillet

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Structure type:: Chapter

Earth Observing System (EOS). A description of the planned instrument may be found in the MODIS Instrument Panel Report (1986) and Salomonson et al. (1989). For the nadir version of the sensor, MODIS-N, there will be 36 spectral bands at a variety of spectral and spatial resolutions and ranging from the blue to the thermal infrared. Because they are relatively narrow, the 19 solar reflective bands (Table 2) were studied to illustrate the potential effects of spectral band shifts should interference filters be used to construct these MODIS-N bandpasses. Forward runs of the 5S atmospheric code were made for no spectral shifts, for partial spectral shifts of 5, 10, and (in some cases) 15 ran, and for full spectral shifts of 5, 10, and (in some cases) 15 nm toward shorter wavelengths. The input conditions were the same as those used for the TM bands in the previous section, except that a water surface reflectance case was also used in addition to the vegetation one. The apparent reflectances at satellite altitude for shifted cases were compared to the apparent reflectance at satellite altitude obtained from the no-shift cases. In the absence of any specific design information, spectral response profiles were synthesized for the MODIS-N bands under consideration. The same shape was used for all bands, but scaled in the wavelength dimension according to the bandwidth. For example, the relative response profile for the 30 nm band at 0.905 micrometers is listed in Table 3, and Figures 6 and 7 illustrate the profiles for the unshifted and shifted bandpasses. Because the 5S code is based on a 5-nm grid, the response values are specified every 5 nm. The complete results are presented in Tables 4-7 and the 10-nm full-shift cases in particular are shown in Figures 8 and 9. Substantial differences arise between the shifted and unshifted results for many of the bandpasses. The key results are as follows. CONCLUDING REMARKS The effect of partial (long-wavelength side only) and full spectral band shifts on radiances output from a radiative transfer code were examined for the reflective TM bands over vegetation and for the reflective MODIS-N bands over vegetation and over water. In the case of TM, the greatest errors due to spectral band shifts occurred in the shorter wavelength bands. For example, in TM band 1, a 25% error occurs for a full shift of 15 nm and a 12% error results from a partial shift of 15 nm. Most MODIS-N bands in the solar reflective spectrum can be affected by spectral filter shifts, with errors of several hundred percent possible in some cases. Full spectral band shifts almost always give rise to larger errors than do partial shifts. The main factors responsible for the effects of spectral shifts on sensor output vary from band to band and can include surface reflectance, gas absorption, solar irradiance, and molecular scattering. ACKNOWLEDGEMENTS The author wishes to thank P.N. Slater for valuable discussions, as well as G. Fedosejevs and A. Kalil for assistance in the preparation of the manuscript. REFERENCES Dinguirard, M., Begni, G., and Leroy, M. (1988), SPOT-1 results after 2 years of flight, Proceedings, SPIE, 924:89-95. Markham, B.L., and Barker, J.L. (1985), Spectral characteristics of the Landsat-4 MSS sensors, Landsat-4 Science Characterization Early Results, 1:1-23-1-56, NASA Conf. Pub. 2355. MODIS Instrument Panel Report (1986), Earth Observing System, Volume lib, National Aeronautics and Space Administration, Code NIT-4, Washington, D.C., 20546-0001. (i) The largest errors due to spectral shifts arise in a water vapour absorption region in the MODIS-N bands at 0.905, 0.936, and 0.940 micrometers, regardless of whether the background surface is water or vegeta tion. Even a 5-nm shift of the 10-nm band at 0.936 micrometers can alter the apparent reflectance at the sensor by 100% (cf. Tables 4 and 6). (ii) In all but a few instances, partial spectral band shifts give rise to smaller errors than full shifts. One exception is the 50-nm band at 0.659 micrometers when observing vegetation, which has a relatively narrow chlorophyll absorption dip in that spectral region (cf. Tables 4 and 5). Salomonson, V.V., Barnes, W.L., Mayroon, P.W., Montgomery, H.E. and Ostrow, H. (1989), MODIS: Advanced Facility Instrument for Studies of the Earth as a System, IEEE Transactions on Geoscience and Remote Sensing, 27:145-153. Suits, G.H., Malila, W.A., and Weller, T.M. (1988), The prospects for detecting spectral shifts due to satellite sensor aging, Remote Sensing of Environment, 26:17-29. Tanré, D., Deroo, C., Duhaut, P., Herman, M., Morcrette, J.J., Perbos, J., and Deschamps, P.Y. (1986), Simulation of the satellite signal in the solar spectrum, Laboratoire d'Optique Atmosphérique, Université des Sciences et Techniques de Lille, 59655 Villeneuve d'Ascq Cédex, France, 343 pages. (iii) Outputs from the 5S code runs were examined to determine the principal spectral variable causing the differences resulting from spectral shifts (cf. Tables 4-7). In about half the MODIS-N bands, surface reflectance is the main factor whereas, in other bands, the principal causative variable can be gas absorption or solar irradiance or, in the case of the band at 0.470 micrometers imaging water, molecular scattering. Teillet, P.M. (1989), Surface Reflectance Retrieval Using Atmospheric Correction Algorithms, Proceedings of the 1989 International Geoscience and Remote Sensing Symposium (IGARSS'89) and the Twelfth Canadian Symposium on Remote Sensing, Vancouver, B.C., pp. 864-867. 60

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