The FLEX-Fluorescence Explorer mission project: motivations and present status of preparatory activities

Abstract

Detecting vegetation fluorescence from space would provide new insight on terrestrial biosphere response to climate variability, and help quantifying atmospheric carbon sequestration. This paper outlines technical and scientific studies undertaken for the preparation of the FLEX-Fluorescence Explorer space mission proposed to ESA in the framework of the Earth Explorer Opportunity Missions program.

Assessing Steady-state Fluorescence and PRI from Hyperspectral Proximal Sensing as Early Indicators of Plant Stress: The Case of Ozone Exposure

“…A global satellite mission for sensing solar-induced fluorescence is currently under evaluation (ESA-FLEX, European Space Agency-FLuorescence EXplorer, [ 53 ]) and will open interesting perspectives for the early detection of plant stress at landscape level. However, upscaling of these methodologies still requires investigation on challenging issues such as the precise correction of atmospheric effects that might influence the estimation of steady-state florescence variables and PRI, recently proven feasible on MERIS satellite data by Guanter et al [ 54 ].…”

Assessment of plant vitality detection through fluorescence and reflectance imagery

“…Thus the velocity and direction of stress impacts can be estimated. But the transfer of this experience in the area of remote sensing requires new investigations to define relations between the high sensitive local changes (which can not be registered from long distance) and the common (for the whole plant) spectral distribution change of the fluorescence intensity (Stoll et al, 2003;Miller et al, 2005).…”

“…The efforts to answer the requirements for fast and reliable environmental control of vegetation leaded to defining new criteria for estimation of the plant state and activity. The widely applied Normalised Difference Vegetation Index (NDVI) (Kidwell, 1990;Stoms and Hargrove, 2000), due to its early saturation (Bushmann and Nagel, 1993), was found to be insufficiently sensitive to changes of medium and high chlorophyll content. That is why two new indices were established, based on the maximal sensitivity of reflectance to the chlorophyll quantity near 550 and 700 nm (Gitelson et al, 1996a).…”

“…Nowadays reflectance spectra are the main optical signatures used for monitoring of plant biomes. However, they provide information mainly related to the total quantity of vegetation and the concentration of its constituents (Stoms and Hargrove, 2000). The efforts to answer the requirements for fast and reliable environmental control of vegetation leaded to defining new criteria for estimation of the plant state and activity.…”

Characterization of the atmosphere during SEN2FLEX 2005 field campaign

“…Monitoring this parameter at global scale would greatly improve the estimates of vegetation photosynthetic activity, allowing a better description of the role of terrestrial vegetation in the global carbon cycle and its response to climate variability under the increasing pressure of human activity [ Davidson et al , 2003]. As currently there are no measurements of this parameter available from satellites, the Fluorescence Explorer (FLEX) project [ Stoll et al , 2003] was proposed to ESA in 1998, with the main aim of global remote sensing of photosynthesis through the use of Fraunhofer lines of the solar spectrum and the atmospheric oxygen absorption bands for passive monitoring of natural sunlight‐induced fluorescence [ Carter et al , 1996]. The exploratory phase of such ESA missions usually include demonstration activities for testing the technical capabilities of the instruments that could be launched into space in future.…”