Transitioning GNSS Interferometric Reflectometry into Operational Use: GNSS H2O

GPS (and more generally, GNSS) instruments are routinely used by surveyors to measure land boundaries and by geophysicists to monitor tectonic motions. Reflected signals measured by these same GNSS instruments can also provide valuable and cost-efficient information about surface soil moisture, snow depth/snow water equivalent, and vegetation water content. A pilot project using GNSS sites from the EarthScope Plate Boundary Observatory in the western U.S. (PBO H2O, http://xenon.colorado.edu/portal) has demonstrated that these hydrologic products can be generated operationally in a time scale that is relevant for weather forecasting, climate studies, and satellite validation. PBO H2O currently generates products for 150 soil moisture sites and 210 snow sites. Each of the GNSS hydrologic products has been validated using in situ measurement campaigns. The spatial scale of the GNSS hydrologic products is ~1000 m^2; temporal sampling is currently 12 hours for soil moisture and 24 hours for snow depth/SWE. Approximately 5 minutes of cpu is needed to update hydrologic products for a GNSS site.

NASA ESTO has funded the development of GNSS H2O. The goal of GNSS H2O is to expand the PBO H2O pilot project to the 12,000+ continuously-operating global GNSS sites. In order to do this, GNSS H2O is leveraging the Apache Object Oriented Data Technology (OODT) framework. This open-source system currently serves as the infrastructure backbone for various JPL, NASA, and non-NASA science data systems. PBO H2O was focused primarily on data from a single GNSS network. The new portal will enable the operators of global GNSS networks to provide raw GNSS data to GNSS H2O. New infrastructure is being developed that will automatically evaluate station metadata for suitability of hydrologic products (i.e. proximity of roads and buildings to the GNSS antenna). By using OODT, GNSS H2O will be able to generate hydrologic products more frequently than PBO H2O's latency, which is currently once/day.