| Autor: |
Christopher J. Crawford, Jeannette van den Bosch, Kelly M. Brunt, Milton G. Hom, John W. Cooper, David J. Harding, James J. Butler, Philip W. Dabney, Thomas A. Neumann, Craig S. Cleckner, Thorsten Markus |
| Jazyk: |
angličtina |
| Rok vydání: |
2018 |
| ISSN: |
1867-8548 |
| Popis: |
Methods to radiometrically calibrate a non-imaging airborne visible-to-shortwave infrared (VSWIR) spectrometer to measure the Greenland Ice Sheet surface are presented. Airborne VSWIR measurement performance is then benchmarked for bright Greenland ice and dark bare rock/soil targets using the MODerate resolution atmospheric TRANsmission (MODTRAN) radiative transfer code (version 6.0), and a coincident Landsat 8 Operational Land Imager (OLI) acquisition on 29 July 2015 during an in-flight radiometric calibration experiment. Airborne remote sensing flights were carried out in northwestern Greenland in preparation for the Ice, Cloud and land Elevation Satellite 2 (ICESat-2) laser altimeter mission. Nine science flights were conducted over the Greenland Ice Sheet, sea ice, and open ocean water. The campaign’s primary purpose was to correlate green laser pulse penetration into snow and ice with spectroscopic derived surface properties. An experimental airborne instrument configuration that included a nadir viewing (downward looking at the surface) non-imaging Analytical Spectral Devices Inc. (ASD) spectrometer that measured at-sensor upwelling VSWIR (0.35 to 2.5 µm) spectral radiance (Watts/m−2/sr−1/nm−1) in the two color Slope Imaging Multi-polarization Photon-Counting Lidar’s (SIMPL) ground Instantaneous Field-of-View, and a zenith viewing (upward looking at the sky) ASD spectrometer that measured at-sensor VSWIR spectral irradiance (Watts/m−2/nm−1) was flown. Rigorous radiometric calibration procedures for laboratory, in-flight, and field environments are described in detail to achieve a targeted at-sensor VSWIR measurement requirement of within 5 % to support calibration/validation (cal/val) efforts and geophysical science algorithm development. Our MODTRAN simulations for the 29 July flight line over dark and bright targets indicate that the nadir viewing airborne VSWIR spectrometer achieved an at-sensor spectral radiance measurement accuracy of between 0.6 and 4.7 % for VSWIR wavelengths (0.4 to 2.0 µm) with atmospheric transmittance greater than 80 %. At-sensor MODTRAN simulations for Landsat 8 OLI relative spectral response functions suggest that OLI is measuring 6 to 16% more at-sensor top-of-atmosphere (TOA) spectral radiance from the Greenland Ice Sheet surface than was observed from the nadir viewing airborne VSWIR spectrometer. While more investigation is required to convert airborne at-sensor VSWIR spectral radiance into atmospherically-corrected airborne surface reflectance, it is expected that airborne science flight data products will contribute to spectroscopic determination of Greenland Ice Sheet surface properties to improve understanding of their potential influence on ICESat-2 measurements. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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