GNSS Reflectometry

Lead Organisation: SSTL

Partners: University of Surrey, the University of Bath, the National Oceanography Centre, Southampton & Polar Imaging Ltd.

This project investigates a new prototype instrument that exploits signals from GPS/GNSS navigation satellites reflected from land, ice and ocean. By analysing the reflected signal with an instrument flying on a separate small satellite, it is possible to derive important scientific data on the nature of the reflecting surface and the atmosphere, such as the sea-surface roughness or soil moisture content. The project will develop a flexible multi-channel receiver for reflected GNSS signals for surface sea-state measurements. It is led by SSTL working with the University of Surrey, the University of Bath, the National Oceanography Centre, Southampton and Polar Imaging Ltd.

Science and Operational Need

The scientific usefulness of GNSS signals for Earth Observation is already well established e.g. for atmospheric sounding to measure tropospheric temperature, pressure and humidity. GNSS signals also prove their worth for Earth Surface Reflectometry. In an experiment from an SSTL satellite in 2003, GPS signals reflected off the Earth surface were used to yield geophysical information about the scattering properties of the ocean, ice and land surfaces.

GNSS signals reflected from the ocean contain information about both sea surface height (altimetry) and ocean roughness (sea state and scatterometry). Ocean roughness impacts many areas of ocean and atmospheric science and is important for operational ocean and weather forecasting. Air-sea exchanges of gases, for example, are controlled by surface roughness, so that better sampling would have a direct impact on our understanding of the magnitude and distribution of atmospheric carbon dioxide (CO2) uptake by the ocean. There are important applications in the prediction of high winds, dangerous sea states, risk of flooding and storm surges.

Project Objectives

The objective of this project is to develop a new prototype instrument that can be applied to both Earth surface reflectometry (ocean, land and ice) and atmospheric sounding together with the consolidation of the science case. Evolving from the successful GNSS-R receiver flown on UK-DMC satellite, the new prototype will incorporate a new multi-channel frontend receiver for both GPS and Galileo signals on two frequencies. It will have re-configurable processing capabilities to allow processing and data collection in real time. Space flight opportunities for this instrument are identified both through SSTL’s own satellite-launching capability and through ESA as an approved addition to a future operational mission (SMOS-ops) to measure soil moisture and ocean salinity.

Contact point for further information: Dr Martin Unwin, SSTL

Published paper on the results from the CEOI-funded GNSS receiver