"We're not talking about actually spotting floating litter items," explains ESA's Paolo Corradi, who is overseeing the project, "but instead to identify a distinct spectral signature of plastic picked up from orbit." The technology would work in the same way as the processing software used in recycling plants, which identifies plastic based on its specific infrared "fingerprints".

At this stage, the teams from France and the UK are assessing how feasible their objective is using current technology from the top of the atmosphere, but Corradi says they may have to operate from the middle of the atmosphere using aircraft or drones, or improve the technology altogether.

He adds that while current simulations estimating the amount of marine plastic "are all well and good", an image based on actual measurements would have greater impact on policymakers. "Monitoring is not a goal in itself, but a means to show the scale of the problem, and start to try and solve it."