Oceanpal®: Monitoring sea state with a GNSS-R coastal instrument.
ABSTRACT Oceanpalreg is a coastal instrument developed at Starlab for operational remote sensing of the ocean surface, with potential direct applications to snow/ice mapping and soil moisture monitoring. The instrument is based on the exploitation of global navigation satellite systems (GNSS) and their augmentation systems (WAAS, EGNOS). The emitted signals provide an exceptional source of opportunity for passive remote sensing of the Earth. The use of GNSS reflections (GNSS-R) for sea-surface monitoring is a bistatic radar technique only requiring a receiving system. The concept has already been implemented for coastal platforms (few meters above the water), aircraft (1km to 10 km) and is being studied for space platforms (LEO, orbiting at 500-1000 km). The potential applications include sea-state, sea-surface altimetry and surface roughness, both for scientific and operational oceanography. We report on a recent long-term experimental and demonstration campaign, carried out at the Oceanpalreg Coeli station in the Barcelona Port during the period 2004-2007, with a real time web-based service. This campaign has been made possible through collaboration with the Barcelona Port Authority Environmental Monitoring Department (APB). The instrument was installed on a breakwater near the main entrance of the port, at 23 m over the sea-surface. We describe in this paper the successful long-term comparison between the data obtained by Oceanpal instrument and the observables recorded by two nearby buoys. Data used for this analysis cover a period of over one year, allowing a definitive evaluation of the performances of this GNSS-R based coastal instrument for SWH retrieval. We also review results from a weeklong phase altimetry campaign at the port of Vilagarcia.