title: GLORI: A GNSS-R Dual Polarization Airborne Instrument for Land Surface Monitoring.
abstract: Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a remote sensing tool, which is complementary to traditional monostatic radars, for the retrieval of geophysical parameters related to surface properties. In the present paper, we describe a new polarimetric GNSS-R system, referred to as the GLObal navigation satellite system Reflectometry Instrument (GLORI), dedicated to the study of land surfaces (soil moisture, vegetation water content, forest biomass) and inland water bodies. This system was installed as a permanent payload on a French ATR42 research aircraft, from which simultaneous measurements can be carried out using other instruments, when required. Following initial laboratory qualifications, two airborne campaigns involving nine flights were performed in 2014 and 2015 in the Southwest of France, over various types of land cover, including agricultural fields and forests. Some of these flights were made concurrently with in situ ground truth campaigns. Various preliminary applications for the characterisation of agricultural and forest areas are presented. Initial analysis of the data shows that the performance of the GLORI instrument is well within specifications, with a cross-polarization isolation better than -15 dB at all elevations above 45°, a relative polarimetric calibration accuracy better than 0.5 dB, and an apparent reflectivity sensitivity better than -30 dB, thus demonstrating its strong potential for the retrieval of land surface characteristics.
authors.affiliation: CESBIO, Université de Toulouse, CNES/CNRS/IRD/UPS, Toulouse, France18 Avenue Edouard Belin, Toulouse Cedex 9 31401, France. erwan.motte@cesbio.cnes.fr.
authors.forename: Erwan
authors.initials: E
authors.lastname: Motte
authors.affiliation: CESBIO, Université de Toulouse, CNES/CNRS/IRD/UPS, Toulouse, France18 Avenue Edouard Belin, Toulouse Cedex 9 31401, France. mehrez.zribi@cesbio.cnes.fr.
authors.forename: Mehrez
authors.initials: M
authors.lastname: Zribi
authors.affiliation: CESBIO, Université de Toulouse, CNES/CNRS/IRD/UPS, Toulouse, France18 Avenue Edouard Belin, Toulouse Cedex 9 31401, France. pascal.fanise@cesbio.cnes.fr.
authors.forename: Pascal
authors.initials: P
authors.lastname: Fanise
authors.affiliation: Cooperative Institute for Climate and Satellites, University of Maryland (CICS-MD/UMD), Appointed at the Laboratory for Satellite Altimetry, National Oceanographic and Atmospheric Administration (NOAA), College Park, MD 20740, USA. alejandro.egido@noaa.gov.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Egido
authors.affiliation: GET, Université de Toulouse, CNRS, IRD, UPS, 14 Avenue Édouard Belin, Toulouse 31400, France. jose.darrozes@get.obs-mip.fr.
authors.forename: José
authors.initials: J
authors.lastname: Darrozes
authors.affiliation: ISPA, INRA, Bordeaux Sciences Agro, Villenave d'Ornon 33140, France. amen.alyaari@bordeaux.inra.fr.
authors.forename: Amen
authors.initials: A
authors.lastname: Al-Yaari
authors.affiliation: IRSTEA, UMR TETIS, 500 Rue François Breton, Montpellier cedex 5 34093, France. nicolas.baghdadi@teledetection.fr.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Baghdadi
authors.affiliation: CESBIO, Université de Toulouse, CNES/CNRS/IRD/UPS, Toulouse, France18 Avenue Edouard Belin, Toulouse Cedex 9 31401, France. frederic.baup@cesbio.cnes.fr.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Baup
authors.affiliation: ISPA, INRA, Bordeaux Sciences Agro, Villenave d'Ornon 33140, France. sylvia.dayau@bordeaux.inra.fr.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Dayau
authors.affiliation: CESBIO, Université de Toulouse, CNES/CNRS/IRD/UPS, Toulouse, France18 Avenue Edouard Belin, Toulouse Cedex 9 31401, France. fieuzalr@cesbio.cnes.fr.
authors.forename: Remy
authors.initials: R
authors.lastname: Fieuzal
authors.affiliation: Matis-IGN/UPEM, 5 Boulevard Descartes, Marne la Vallée Cedex 2 77454, France. pierre-louis.frison@u-pem.fr.
authors.forename: Pierre-Louis
authors.initials: PL
authors.lastname: Frison
authors.affiliation: ISPA, INRA, Bordeaux Sciences Agro, Villenave d'Ornon 33140, France. guyon@bordeaux.inra.fr.
authors.forename: Dominique
authors.initials: D
authors.lastname: Guyon
authors.affiliation: ISPA, INRA, Bordeaux Sciences Agro, Villenave d'Ornon 33140, France. wigneron@bordeaux.inra.fr.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Wigneron
keywords: GNSS-R; GPS; L-Band; airborne; biomass; microwave; multistatic radar; reflectometry; soil moisture; vegetation