SARGO: System for Acquisition of Reflected GNSS for Oceanography
A private Portuguese space engineering company developed SARGO - Remote Sensing system for Oceanography. It was developed for centimetre resolution altimetry. Future evolutions will include detection of ocean roughness, waves and surface wind. Core attributes are ease of installation and operation, low maintenance, resilience to adverse conditions and the degree of automation.
SARGO is a system for probing water characteristics through the analysis of signals reflected from the water surface. It is dedicated to the high-resolution determination of water height and characterisation of the water?s state, including wave height, wave frequency, water surface roughness, and water surface wind speeds. The SARGO instrument can work with both GPS and Galileo signals, including the high-bandwidth Galileo E5 frequency band.
The concept of using satellite navigation signals for reflectometry purposes is akin to a bi-static radar, in which the instrument simultaneously acquires both the direct and reflected signals from the GPS/Galileo satellites. Upon reflection from the water surface, the signal is altered by the surface properties, enabling its use for remote sensing the water characteristics.
Applications of Remote Sensing with reflected GNSS (GNSS-R) are many and varied, not only for probing the water surface, including water surface height, wave frequency and height and surface winds, but also for biomass estimation, monitoring of vegetation growth, snow and ice, soil moisture, among others.
The SARGO system consists of data acquisition and data processing subsystems. It is developed by DEIMOS Engenharia, based on the DEIMOS GRIP advanced receiver for high-resolution GNSS applications, and is focused on exploring the potential of the available GNSS signals
DEIMOS Engenharia is part of the Elecnor-DEIMOS Group, leaders in the area of space technology, both in Earth Observation and the GNSS field. DEIMOS Engenharia is involved in ESA?s GEROS mission relating to the use of GNSS signals for Earth Observation, and is leading the European FP7 research project E-GEM, dedicated to the development of GNSS-R technologies for Earth Observation (ocean, land and cryosphere).
Innovations & Advantages
For a ground-mounted instrument such as SARGO, the possibility of detecting remotely the reflected signals from the water surface provides an important advantage relative to traditional instruments deployed on or below the water such as buoys, bubble or pressure sensors. In fact, remote altimetry devices such as radar and ultrasound sensors have been steadily gaining acceptance, as a result of the technology's maturity and corresponding price drop for operational setups.
SARGO is a passive instrument, and behaves like a bi-static radar, with the corresponding advantages of simplification, due to the absence of the emitting components of the radar.
In comparison with existing instruments, SARGO has also the additional flexibility of installation, since it is not required to be mounted directly above the water (as radar and ultrasound sensors do), but can be installed at an angle from the vertical. This feature alone makes this technology interesting for hard-to-reach locations, where downward-pointing to the water surface is difficult.
Current and Potential Domains of Application
Remote sensing of water surface for inland and coastal waters. Applications in:
- Tide, water level and wave monitoring by Port Authorities;
- Seashore monitoring by mandated national authorities;
- Determination of water levels and quantity for inland waters;
- Water flux monitoring and support to flood forecast systems in rivers;
- Integration in higher-level chains, both operational and research oriented