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Chlorophyll Fluorescence Imaging Spectrometer (CFIS), mapping far red fluorescence from aircraft

Frankenberg, Christian and Köhler, Philipp and Magney, Troy S. and Geier, Sven and Lawson, Peter and Schwochert, Mark and McDuffie, James and Drewry, Darren T. and Pavlick, Ryan and Kuhnert, Andreas (2018) Chlorophyll Fluorescence Imaging Spectrometer (CFIS), mapping far red fluorescence from aircraft. Remote Sensing of Environment, 217 . pp. 523-536. ISSN 0034-4257. http://resolver.caltech.edu/CaltechAUTHORS:20180910-101446482

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Abstract

The Chlorophyll Fluorescence Imaging Spectrometer (CFIS) is an airborne high resolution imaging spectrometer built at NASA's Jet Propulsion Laboratory (JPL) for evaluating solar-induced fluorescence (SIF) from the Orbiting Carbon Observatory-2 (OCO-2). OCO-2 is a NASA mission designed to measure atmospheric CO_2 but one of the novel data products is SIF, retrieved using reductions in the optical depth of Fraunhofer lines in OCO-2’s O_2 A-band, covering 757–775 nm at 0.042 nm spectral resolution. CFIS was specifically designed to retrieve SIF within the wavelength range of OCO-2, but extends further down to 737 nm, nearly maintaining the high spectral resolution of the OCO-2 instrument (0.07 vs. 0.042 nm). Here, we provide an overview of the instrument calibration and performance as well as the retrieval strategy based on non-linear weighted least-squares. To illustrate the retrieval performance using actual flight data, we focus on data acquired over agricultural fields in Mead, Nebraska from an unpressurized Twin Otter (DHC-6) aircraft at a flight altitude of 3000 m above ground level (AGL). Spectral residuals are consistent with expected detector noise, which enables us to compute realistic 1-σ precision errors of 0.5–0.7 W/m^2/sr/μm for typical SIF retrievals, which can be reduced to <0.2 W/m^2/sr/μm when individual data is gridded at 30 m spatial resolution. The 30 m resolution also enabled direct comparison with the Crop Data Layer from the National Agricultural Statistics Service as well as Landsatimagery (NDVI, EVI, T_(skin)), taken just a day prior to the CFIS overflights. Results show consistently higher vegetation indices and SIF values over soy fields compared to corn, likely due to the respective phenological stage, which might already have affected chlorophyll content and canopy structure (August 15, 2016). While this work is intended to highlight the technical capabilities and performance of CFIS, the comparisons against Landsat and crop types provide insights into how CFIS can be used to study mechanisms related to photosynthesis at fine spatial scales, with the fidelity needed to obtain un-biased SIF retrievals void of atmospheric correction.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.rse.2018.08.032DOIArticle
ORCID:
AuthorORCID
Frankenberg, Christian0000-0002-0546-5857
Köhler, Philipp0000-0002-7820-1318
Geier, Sven0000-0002-3948-9339
Additional Information:© 2018 Elsevier Inc. Received 12 December 2017, Revised 18 June 2018, Accepted 25 August 2018, Available online 8 September 2018. The research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. ©2018. Additional funding from NASA's Terrestrial Ecology program is acknowledged (16-TE16-0034).
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
NASA16-TE16-0034
Subject Keywords:Chlorophyll fluorescence; CFIS; GPP; OCO; OCO-2
Record Number:CaltechAUTHORS:20180910-101446482
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180910-101446482
Official Citation:Christian Frankenberg, Philipp Köhler, Troy S. Magney, Sven Geier, Peter Lawson, Mark Schwochert, James McDuffie, Darren T. Drewry, Ryan Pavlick, Andreas Kuhnert, The Chlorophyll Fluorescence Imaging Spectrometer (CFIS), mapping far red fluorescence from aircraft, Remote Sensing of Environment, Volume 217, 2018, Pages 523-536, ISSN 0034-4257, https://doi.org/10.1016/j.rse.2018.08.032. (http://www.sciencedirect.com/science/article/pii/S0034425718304085)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89482
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Sep 2018 18:13
Last Modified:10 Sep 2018 18:13

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