Greek researchers enlist EU satellite against Aegean sea litter

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LESBOS ISLAND, Greece, April 22, 2019 (BSS/AFP) – Knee-deep in water on a
picture-postcard Lesbos island beach, a team of Greek university students
gently deposits a wall-sized PVC frame on the surface before divers moor it
at sea.

Holding in plastic bags and bottles, four of the 5 metre-by-5-metre (16
foot-by-16-foot) frames are part of an experiment to determine if seaborne
litter can be detected with EU satellites and drones.

“This was the first big day,” says project supervisor Konstantinos
Topuzelis, an assistant professor at the University of the Aegean department
of Marine Sciences, said of the scene from last week.

“All the targets were carried into the sea, the satellites passed by and
we’re ready to fill out the first report.”

The results of the experiment — “Satellite Testing and Drone Mapping for
Marine Plastics on the Aegean Sea” — by the university’s Marine Remote
Sensing Group will be presented at a European Space Agency symposium in Milan
in May.

“Marine litter is a global problem that affects all the oceans of the
world,” Topouzelis told AFP.

Millions of tonnes of plastic end up in the oceans, affecting marine
wildlife all along the food chain.

“Modern techniques are necessary to detect and quantify marine plastics in
seawater,” Topouzelis added, noting that space agencies have already been
looking into how drones and satellites can help with the clean-up.

“The main advantage is that we are using existing tools,” which brings
down costs and makes it easier to scale up, says Dimitris Papageorgiou, one
of the 60 undergraduate and postgraduate students who worked on the
experiment.

To prepare, the team gathered some 2,000 plastic bottles and lashed them
to the frames. Other targets were crafted with plastic bags, as these are
even harder to spot in the water and usually constitute the deadliest threat
to Aegean marine life such as dolphins, turtles and seals.

In 2018, a first phase in the experiment was able to detect large targets
of around 100 square metres from space.

This year’s experiment uses targets a quarter that size to test the
smallest detectable area under various weather conditions.

“It was a crazy idea,” laughs Topouzelis.

“We knew that the European satellite system passes at regular intervals
with a spatial resolution of 10 metres.”

In theory, then, the satellites should be able to detect the floating
rafts of plastic the team pushed out to sea.

The University of the Aegean is working on the project with Universidad de
Cadiz in Spain, CNR-Ismar in Italy and UK environmental consultants Argans
Ltd.

Satellite data is provided free from the European Space Agency (ESA) and
hours after the overpass targets should be detected from the Sentinel-2
satellite.

The project acts as a calibration and validation exercise on the detection
capabilities of the satellites.

But even if relatively small patches of plastic garbage can be spotted
from orbiting satellites, the problem of how to remove it from the sea
remains.

Last year, a giant floating barrier five years in the making was launched
off the coast of San Francisco, as part of a $20-million project to clean up
a swirling island of rubbish between California and Hawaii.

But the slow speed of the solar-powered barrier prevents it from holding
onto the plastic after it scoops it up.