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PhotoSpec: A new instrument to measure spatially distributed red and far-red Solar-Induced Chlorophyll Fluorescence

Grossmann, Katja and Frankenberg, Christian and Magney, Troy S. and Hurlock, Stephen C. and Seibt, Ulrike and Stutz, Jochen (2018) PhotoSpec: A new instrument to measure spatially distributed red and far-red Solar-Induced Chlorophyll Fluorescence. Remote Sensing of Environment, 216 . pp. 311-327. ISSN 0034-4257. doi:10.1016/j.rse.2018.07.002.

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Solar-Induced Chlorophyll Fluorescence (SIF) is an emission of light in the 650–850 nm spectral range from the excited state of the chlorophyll-a pigment after absorption of photosynthetically active radiation (PAR). As this is directly linked to the electron transport chain in oxygenic photosynthesis, SIF is a powerful proxy for photosynthetic activity. SIF observations are relatively new and, while global scale measurements from satellites using high-resolution spectroscopy of Fraunhofer bands are becoming more available, observations at the intermediate canopy scale using these techniques are sparse. We present a novel ground-based spectrometer system - PhotoSpec - for measuring SIF in the red (670–732 nm) and far-red (729–784 nm) wavelength range as well as canopy reflectance (400–900 nm) to calculate vegetation indices, such as the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), and the photochemical reflectance index (PRI). PhotoSpec includes a 2D scanning telescope unit which can be pointed to any location in a canopy with a narrow field of view (FOV = 0.7°). PhotoSpec has a high signal-to-noise ratio and spectral resolution, which allows high precision solar Fraunhofer line retrievals over the entire fluorescence wavelength range under all atmospheric conditions using a new two-step linearized least-squares retrieval procedure. Initial PhotoSpec observations include the diurnal SIF cycle of single broad leaves, grass, and dark-light transitions. Results from the first tower-based measurements in Costa Rica show that the instrument can continuously monitor SIF of several tropical species throughout the day. The PhotoSpec instrument can be used to explore the relationship between SIF, photosynthetic efficiencies, Gross Primary Productivity (GPP), and the impact of canopy radiative transfer, viewing geometry, and stress conditions at the canopy scale.

Item Type:Article
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URLURL TypeDescription
Frankenberg, Christian0000-0002-0546-5857
Magney, Troy S.0000-0002-9033-0024
Additional Information:© 2018 Elsevier Inc. Received 30 November 2017, Revised 19 June 2018, Accepted 2 July 2018, Available online 13 July 2018. This work is funded in part by the W.M. Keck Institute for Space Studies and internal funds from the Jet Propulsion Laboratory ( The authors would like to thank A. Pivovaroff (La Kretz Center for California Conservation Science, University of California Los Angeles, Los Angeles, CA, USA) for the assistance with the PAM-2500 measurements of single leaves on the UCLA Math Sciences building in 2016. The research project at La Selva Biological Station, Costa Rica, is supported by the NSF Career award (grant # 1455381) and the ECTS-R (Emerging Challenges in Tropical Science-Research) research fellowship provided by the Organization for Tropical Studies (OTS). The authors would like to thank the OTS staff at La Selva, especially D. Dierick, for their continuous help and support with the PhotoSpec installation and maintenance.
Group:Keck Institute for Space Studies
Funding AgencyGrant Number
Keck Institute for Space Studies (KISS)UNSPECIFIED
Organization for Tropical Studies (OTS)UNSPECIFIED
Subject Keywords:Solar-Induced Chlorophyll Fluorescence (SIF); Photosynthesis; Remote sensing
Record Number:CaltechAUTHORS:20180716-083038568
Persistent URL:
Official Citation:Katja Grossmann, Christian Frankenberg, Troy S. Magney, Stephen C. Hurlock, Ulrike Seibt, Jochen Stutz, PhotoSpec: A new instrument to measure spatially distributed red and far-red Solar-Induced Chlorophyll Fluorescence, Remote Sensing of Environment, Volume 216, 2018, Pages 311-327, ISSN 0034-4257, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87865
Deposited By: Tony Diaz
Deposited On:16 Jul 2018 16:30
Last Modified:16 Nov 2021 00:21

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