Ocean colour seen

Researchers are designing a system that will help even non-expert users observe the world’s coastal waters more accurately than ever before.

A consortium of some of Europe’s leading oceanographers are creating a system called Marsais (Marine SAR Analysis and Interpretation System) that aims to take full advantage of new data provided by the Advanced Synthetic Aperture Radar (ASAR) devices aboard the new environmental monitoring satellite Envisat, which was launched earlier this year.

Led by Norway’s Nansen Environmental and Remote Sensing Centre, the Marsais group also includes the Southampton Oceanography Centre and the Coastal Resources Centre at University College Cork (UCC).

When completed in 2004, Marsais, an EU backed project, could help track more effectively pollutants such as potentially dangerous algae blooms and oil slicks, and monitor currents and shipping traffic. It also hopes to play a major role in the development of sustainable fishing stocks by warning of changing conditions in coastal waters.

SAR (Synthetic Aperture Radar) sensors themselves fire microwave pulses to the earth’s surface and receive back the reflected signals, which can then be used to generate high-resolution images of the terrain the satellite has passed over. The advantage of SAR over other types of earth observation techniques, especially optical ones, is its ability to work regardless of cloud cover and in all lighting conditions.

Limited SAR data has been available from earlier satellites, and the technology has mainly been used for land observation and military applications. SAR devices were aboard the European remote sensing satellites ERS-1 and ERS-2, which were launched in 1991 and 1995, respectively, providing images of the earth’s surface with a resolution of 25m.

The Envisat satellite, however, contains an Advanced Synthetic Aperture Radar (ASAR) that features enhanced capability in terms of coverage, range of incidence angles, polarisation, and modes of operation.

Hence the new satellite will provide superior quality data more frequently, as it scans swathes of the earth’s surface up to five times bigger than previously possible.

According to Marsais, these ASARs will herald a ‘new era of unique opportunities’ for marine observation, especially around coastal regions.

The consortium will build a database containing data collected from the new satellite as well as data from other satellites; software will then be developed to provide highly accurate images of the ocean from the data and tools developed to allow users to analyse the images. In addition, the developers will create a user-friendly interface so that the system can be used by ‘non-expert’ individuals.

Cathal O’Mahony, a researcher working on UCC’s Marsais team, says that ‘(the system) needs to be very user friendly, because many people employing the system are likely to be unfamiliar with using SAR data or may not know anything about the technology at all,’ said O’Mahony.

He said possible markets for the system include the offshore oil and gas industry, academics, harbour authorities and firms involved in aquaculture and pollution control.

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