Interferometry based orbit observation for geosynchronous synthetic aperture radar (GEOSAR) missions

A major limitation of current Low Earth Orbit Synthetic Aperture Radars (LEOSAR) is related to their revisit time of several days or weeks. They cannot provide continuous monitoring over the same area of the planet. The introduction of the Geosynchronous Synthetic Aperture Radar (GEOSAR) aims to provide permanent illumination over a wide zone of the planet. This work is performed in the context of the new ESA Earth Explorer pre-selected mission G-CLASS/Hydroterra. It is designed to help scientists unravel the details of the daily water cycle. The orbit determination of a GEOSAR is one of the main challenges of the mission. Previous studies show how the generic sub-wavelength tolerance requirement to build a well focused synthetic aperture can be substantially relaxed up to the sub-meter scale. Several orbit observation techniques are reliable and perform well to this end. Among them, interferometry stands out since it can provide orbit observables coming from current satellites operating in GEO, serving as illuminators of opportunity. The experimental orbit observation data resulting from the validation interferometer built at the campus of the Universitat Politècnica de Catalunya in Barcelona is presented. It depicts the expected motion of the ASTRA 1M satellite, serving as proof of concept for future GEOSAR missions such as G-CLASS/Hydroterra.This work has been supported by the SpanishScience, Research and Innovation Plan (MINECO)withProject Codes TIN2014-55413-C2-1-P and TEC2017-85244-C2-2-P and by Unidad de Excelencia Maria deMaeztu MDM-2016-0600 financed by the AgenciaEstatal de Investigación, Spain.Peer ReviewedObjectius de Desenvolupament Sostenible::6 - Aigua Neta i SanejamentObjectius de Desenvolupament Sostenible::3 - Salut i BenestarObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::15 - Vida d'Ecosistemes TerrestresObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (author's final draft