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.
Highlights
Physical soil and vegetation characteristics play an essential role in the functioning of continental water and carbon cycles [1,2]
The Delay-Doppler Map (DDM) |Yr pτ, f q|2 corresponds to the GNSS power the Woodward ambiguity function (WAF), the DDM points can be related to contributions from cells on the surface which correspond scattered by the surface, as a function of delay and Doppler frequency
Some very preliminary results of the experimental campaign and of the quality of of the GLObal navigation satellite system Reflectometry Instrument (GLORI) measurements are illustrated over the forest (Zone 3) and the agricultural (Zone 4)
Summary
Physical soil and vegetation characteristics play an essential role in the functioning of continental water and carbon cycles [1,2]. Over the last 20 years, experimental and theoretical studies made with GNSS-R have demonstrated its true potential for the evaluation of Earth surface characteristics This technique was first developed for the measurement of sea surface parameters such as height [6] and roughness [7], other more recent studies have focused on the monitoring of land surface characteristics such as soil moisture [8,9], fraction of vegetation cover [10,11], forest biomass [12,13], the mapping of flooded areas [14], and the detection of snow or ice [15,16].
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