Advanced radiometry measurements and Earth science applications with the Airborne Prism Experiment (APEX)

By Michael E. Schaepman, M. Jehle, A. Hueni, P. D'Odorico, Alexander Damm, J. Weyermann, Fabian D. Schneider, Valerie C. E. Laurent, C. Popp, F. Seidel and 11 more. 2015

199 citations recorded by the source corpus.

Abstract We present the Airborne Prism Experiment (APEX), its calibration and subsequent radiometric measurements as well as Earth science applications derived from this data. APEX is a dispersive pushbroom imaging spectrometer covering the solar reflected wavelength range between 372 and 2540 nm with nominal 312 (max. 532) spectral bands. APEX is calibrated using a combination of laboratory, in-flight and vicarious calibration approaches. These are complemented by using a forward and inverse radiative transfer modeling approach, suitable to further validate APEX data. We establish traceability of APEX radiances to a primary calibration standard, including uncertainty analysis. We also discuss the instrument simulation process ranging from initial specifications to performance validation. In a second part, we present Earth science applications using APEX. They include geometric and atmospheric compensated as well as reflectance anisotropy minimized Level 2 data. Further, we discuss retrieval of aerosol optical depth as well as vertical column density of NOx, a radiance data-based coupled canopy–atmosphere model, and finally measuring sun-induced chlorophyll fluorescence (Fs) and infer plant pigment content. The results report on all APEX specifications including validation. APEX radiances are traceable to a primary standard with  625 for all spectral bands. Radiance based vicarious calibration is traceable to a secondary standard with ≤ 6.5% uncertainty. Except for inferring plant pigment content, all applications are validated using in-situ measurement approaches and modeling. Even relatively broad APEX bands (FWHM of 6 nm at 760 nm) can assess Fs with modeling agreements as high as R2 = 0.87 (relative RMSE = 27.76%). We conclude on the use of high resolution imaging spectrometers and suggest further development of imaging spectrometers supporting science grade spectroscopy measurements.

Subfields: Ecology, Environmental Engineering, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/b2a8bcf029ad75028eb9b222e556785b2090d3cd

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In Ecology

1. Wolfram Mauser
2. Pedro J. Leitão
3. Patrick Hostert
4. Tobias B. Hank
5. Luis Guanter

In Environmental Engineering

1. Wolfram Mauser
2. Pedro J. Leitão
3. Patrick Hostert
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In Global and Planetary Change

1. Wolfram Mauser
2. Pedro J. Leitão
3. Tobias B. Hank

Citations in the corpus

• The EnMAP Spaceborne Imaging Spectroscopy Mission for Earth Observation (2015, methodology): “Other airborne imaging spectrometers widely used in the last few years are HyMAP [28], the Compact Airborne Spectrographic Imager (CASI) [29] and the Airborne Prism Experiment (APEX) [30,31].”
• SelfS2: Self-Supervised Transfer Learning for Sentinel-2 Multispectral Image Super-Resolution (2023, unknown): “…from the HYDICE images of Washington DC Mall and Terrain (respectively, denoted as “HYDICE-WDC” and “HYDICE-Terrain”) with 2.8-m spatial resolution, and the remaining one comes from the airborne prism experiment (APEX) [60] image of Baden (denoted as “APEX-Baden”) with 1.8-m spatial resolution.”