{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T05:03:40Z","timestamp":1787029420703,"version":"3.56.0"},"reference-count":63,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2020,5,19]],"date-time":"2020-05-19T00:00:00Z","timestamp":1589846400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010661","name":"Horizon 2020","doi-asserted-by":"publisher","award":["721995"],"award-info":[{"award-number":["721995"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Chlorophyll fluorescence (ChlF) information offers a deep insight into the plant physiological status by reason of the close relationship it has with the photosynthetic activity. The unmanned aerial systems (UAS)-based assessment of solar induced ChlF (SIF) using non-imaging spectrometers and radiance-based retrieval methods, has the potential to provide spatio-temporal photosynthetic performance information at field scale. The objective of this manuscript is to report the main advances in the development of UAS-based methods for SIF retrieval with non-imaging spectrometers through the latest scientific contributions, some of which are being developed within the frame of the Training on Remote Sensing for Ecosystem Modelling (TRuStEE) program. Investigations from the Universities of Edinburgh (School of Geosciences) and Tasmania (School of Technology, Environments and Design) are first presented, both sharing the principle of the spectroradiometer optical path bifurcation throughout, the so called \u2018Piccolo-Doppio\u2019 and \u2018AirSIF\u2019 systems, respectively. Furthermore, JB Hyperspectral Devices\u2019 ongoing investigations towards the closest possible characterization of the atmospheric interference suffered by orbital platforms are outlined. The latest approach focuses on the observation of one single ground point across a multiple-kilometer atmosphere vertical column using the high altitude UAS named as AirFloX, mounted on a specifically designed and manufactured fixed wing platform: \u2018FloXPlane\u2019. We present technical details and preliminary results obtained from each instrument, a summary of their main characteristics, and finally the remaining challenges and open research questions are addressed. On the basis of the presented findings, the consensus is that SIF can be retrieved from low altitude spectroscopy. However, the UAS-based methods for SIF retrieval still present uncertainties associated with the current sensor characteristics and the spatio-temporal mismatching between aerial and ground measurements, which complicate robust validations. Complementary studies regarding the standardization of calibration methods and the characterization of spectroradiometers and data processing workflows are also required. Moreover, other open research questions such as those related to the implementation of atmospheric correction, bidirectional reflectance distribution function (BRDF) correction, and accurate surface elevation models remain to be addressed.<\/jats:p>","DOI":"10.3390\/rs12101624","type":"journal-article","created":{"date-parts":[[2020,5,20]],"date-time":"2020-05-20T02:48:24Z","timestamp":1589942904000},"page":"1624","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":44,"title":["Unmanned Aerial Systems (UAS)-Based Methods for Solar Induced Chlorophyll Fluorescence (SIF) Retrieval with Non-Imaging Spectrometers: State of the Art"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6524-7504","authenticated-orcid":false,"given":"Juan Quir\u00f3s","family":"Vargas","sequence":"first","affiliation":[{"name":"Institute of Biogeosciences, IBG2: Plant Sciences, Forschungszentrum J\u00fclich GmbH, 52425 J\u00fclich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6454-5654","authenticated-orcid":false,"given":"Juliane","family":"Bendig","sequence":"additional","affiliation":[{"name":"School of Technology, Environments and Design, University of Tasmania, Hobart, TAS 7001, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alasdair","family":"Mac Arthur","sequence":"additional","affiliation":[{"name":"School of Geosciences, University of Edinburgh, Edinburgh EH9 3FF, UK"},{"name":"Laboratory for Earth Observation, Image Processing Laboratory, University of Valencia, 46980 Valencia, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andreas","family":"Burkart","sequence":"additional","affiliation":[{"name":"JB Hyperspectral Devices UG, Am Botanischen Garten 33, D\u00fcsseldorf 40225, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tommaso","family":"Julitta","sequence":"additional","affiliation":[{"name":"JB Hyperspectral Devices UG, Am Botanischen Garten 33, D\u00fcsseldorf 40225, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3299-4380","authenticated-orcid":false,"given":"Kadmiel","family":"Maseyk","sequence":"additional","affiliation":[{"name":"School of Environment, Earth &amp; Ecosystem Sciences, The Open University, Milton Keynes MK7 6AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8307-2584","authenticated-orcid":false,"given":"Rick","family":"Thomas","sequence":"additional","affiliation":[{"name":"Birmingham Institute of Forest Research (BIFoR), University of Birmingham, Birmingham B15 2TT, UK"},{"name":"Big Sky Science Ltd., Sutton Coldfield B72 1SY, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bastian","family":"Siegmann","sequence":"additional","affiliation":[{"name":"Institute of Biogeosciences, IBG2: Plant Sciences, Forschungszentrum J\u00fclich GmbH, 52425 J\u00fclich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6052-3140","authenticated-orcid":false,"given":"Micol","family":"Rossini","sequence":"additional","affiliation":[{"name":"Remote Sensing of Environmental Dynamics Laboratory, Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Piazza della Scienza1, 20126 Milano, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7249-7106","authenticated-orcid":false,"given":"Marco","family":"Celesti","sequence":"additional","affiliation":[{"name":"Remote Sensing of Environmental Dynamics Laboratory, Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Piazza della Scienza1, 20126 Milano, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dirk","family":"Sch\u00fcttemeyer","sequence":"additional","affiliation":[{"name":"ESA-ESTEC, 2201 AZ Noordwijk, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9451-6769","authenticated-orcid":false,"given":"Thorsten","family":"Kraska","sequence":"additional","affiliation":[{"name":"Field Lab Campus Klein-Altendorf, University of Bonn, 53359 Rheinbach, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0473-5632","authenticated-orcid":false,"given":"Onno","family":"Muller","sequence":"additional","affiliation":[{"name":"Institute of Biogeosciences, IBG2: Plant Sciences, Forschungszentrum J\u00fclich GmbH, 52425 J\u00fclich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9993-4588","authenticated-orcid":false,"given":"Uwe","family":"Rascher","sequence":"additional","affiliation":[{"name":"Institute of Biogeosciences, IBG2: Plant Sciences, Forschungszentrum J\u00fclich GmbH, 52425 J\u00fclich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,5,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1007\/s11120-016-0318-y","article-title":"Frequently asked questions about chlorophyll fluorescence, the sequel","volume":"132","author":"Kalaji","year":"2017","journal-title":"Photosynth. 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