Radiometric calibration of a non-imaging airborne spectrometer to measure the Greenland ice sheet surface
<p>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 for bright Greenland ice and dark bare rock/soil targets is compared against the MO...
Main Authors: | , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2019-03-01
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Series: | Atmospheric Measurement Techniques |
Online Access: | https://www.atmos-meas-tech.net/12/1913/2019/amt-12-1913-2019.pdf |
Summary: | <p>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 for
bright Greenland ice and dark bare rock/soil targets is compared against the
MODerate resolution atmospheric TRANsmission (MODTRAN<sup>®</sup>)
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. A total of 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 (looking downward at
the surface) non-imaging Analytical Spectral Devices (ASD) Inc. spectrometer
that measured upwelling VSWIR (0.35 to 2.5 <span class="inline-formula">µ</span>m) spectral radiance
(<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">W</mi><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">2</mn></mrow></msup><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">sr</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">µ</mi><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="81pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="c12b79b6a3c597d34641ede95b2f39cf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-12-1913-2019-ie00001.svg" width="81pt" height="15pt" src="amt-12-1913-2019-ie00001.png"/></svg:svg></span></span>) in the two-color Slope Imaging
Multi-polarization Photon-Counting Lidar's (SIMPL) ground instantaneous
field of view, and a zenith-viewing (looking upward at the sky) ASD
spectrometer that measured VSWIR spectral irradiance
(W m<span class="inline-formula"><sup>−2</sup></span> nm<span class="inline-formula"><sup>−1</sup></span>) was flown. National Institute of Standards and
Technology (NIST) traceable radiometric calibration procedures for
laboratory, in-flight, and field<span id="page1914"/> environments are described in detail to
achieve a targeted VSWIR measurement requirement of within 5 % to support
calibration/validation efforts and remote sensing algorithm development. Our
MODTRAN predictions for the 29 July flight line over dark and bright targets
indicate that the airborne nadir-viewing spectrometer spectral radiance
measurement uncertainty was between 0.6 % and 4.7 % for VSWIR wavelengths
(0.4 to 2.0 <span class="inline-formula">µ</span>m) with atmospheric transmittance greater than 80 %.
MODTRAN predictions for Landsat 8 OLI relative spectral response functions
suggest that OLI is measuring 6 % to 16 % more top-of-atmosphere (TOA)
spectral radiance from the Greenland ice sheet surface than was predicted
using apparent reflectance spectra from the nadir-viewing spectrometer.
While more investigation is required to convert airborne 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 optical
properties to improve understanding of their potential influence on ICESat-2
measurements.</p> |
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ISSN: | 1867-1381 1867-8548 |