Airborne GNSS-R: A key enabling technology for environmental monitoring

Weather forecast using GNSS-R relies, to a large extent, on data acquired by airborne and spaceborne platforms due to the extended coverage that can be achieved. GEO satellites can retrieve measurements over large areas but with spatial resolutions on the order of thousands of meters per pixel. LEO satellites with polar orbits can provide measurements over the entire world, but they cannot provide good spatial or high temporal resolutions by themselves. LEO constellations of small satellites have the same coverage with improved spatial resolution and revisit times by using data fusion techniques. High-altitude pseudo-satellites offer an excellent temporal and spatial resolution but only over limited areas. In this article, the potential of using hosted GNSS-R payloads on commercial aircraft is explored as an alternative and cost-effective means to achieve a very high resolution and a very low revisit time for regional environmental applications. Finally, a case study of soil moisture monitoring over Europe is presented, including an analysis of the expected performance. This work was supported in part by the projects of Spanish Ministerio de Ciencia, Innovación y Universidades and EU ERDF project un- der Grant RTI2018-099008-B-C21/AEI/10.13039/501100011033 “SENSING WITH PIONEERING OPPORTUNISTIC TECHNIQUES,” in part by the Grant MDM-2016-0600 to “Maria de Maeztu Excellence Research Units” CommSensLab, from Spanish Ministerio de Economía y Competitividad (MINECO/FEDER), and in part by the Recruitment of Early-Stage Research Staff under Grant FI-SDUR 2020 - 00105 of the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR).