Oceanpal®, a GPS-reflection coastal instrument to monitor sea-state

Paper number

IAC-06-B1.3.06

Author

Mr. Marco Caparrini, Starlab Barcelona SL, Spain

Coauthor

Mr. Stephen Dunne, Starlab Barcelona SL, Spain

Coauthor

Mr. Olivier Germain, Starlab Barcelona SL, Spain

Coauthor

Dr. Esteve Farrés, Starlab Barcelona SL, Spain

Coauthor

Dr. François Soulat, Starlab Barcelona SL, Spain

Coauthor

Dr. Giulio Ruffini, Starlab Barcelona SL, Spain

Year

2006

Abstract

The Global Navigation Satellite Systems (GNSS, such as the GPS and GLONASS constellations) and their augmentation systems (WAAS, EGNOS) constitute premium sources of opportunity for passive remote sensing. By 2010, after the deployment of the European Galileo constellation, more than 50 GNSS satellites will be emitting self-calibrating, dual-frequency, rain-immune, L-band spread spectrum signals, with long-term availability and stability. 

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 from coastal platforms (few tens of meters above the water), effectively demonstrated from aircraft (1 km to 10 km) and successfully proved in space (LEO, orbiting at 500 km). The potential applications include sea-surface altimetry, sea-state, surface roughness, surface currents and salinity, both for scientific and operational oceanography.

In this paper, we discuss Oceanpal, Starlab’s GNSS-R instrument for coastal applications. Oceanpal features two antennas: one RHCP, zenith-looking antenna collects the direct GPS signal while one LHCP, nadir-looking antenna recovers the reflected signal. Each antenna acquires simultaneous data bursts of some minutes which are sampled at 16 MHz and recorded. The data is then fed into the Oceanpal’s processor, Starlight, which retrieves both the direct and reflected complex electromagnetic fields (Level 0 products). 

Presently, Oceanpal can deliver two products. The fist one is the antenna height over the reflecting surface. This is measured by analyzing the phase delay between the reflected and direct signal. The precision of this measurement is of the order of 2 cm in calm waters (e.g., inside a harbour). In rough waters, estimation is based on code ranging, thus performance is expected to degrade. The second one is the significant wave height, based on an estimation of the reflected signal coherence time which is linked to sea-surface surface motion. Coherence time can be related to SWH with a precision of the order of 10 cm using a semi-empirical algorithm adapted to the coastal region of interest. These products are then stored in the data management unit which also acts as a web server to provide the information to any remote user via a web browser interface.

Abstract document

IAC-06-B1.3.06.pdf

Manuscript document

IAC-06-B1.3.06.pdf (🔒 authorized access only).

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