58 If however the USV’s job is only to collect litter, GPA Seabots recommends removing the container floats and absorbers to minimise drag in the water and maximise the amount of room for litter inside the basket. Different baskets are also available, including some with plastic bristles around the mouth to prevent litter from floating back out into the harbour. CONOPS for cleaning While MWIR cameras are increasingly popular for detecting spilled or leaking hydrocarbons, the presence of oil in harbours is often easily detected visually, particularly in Spanish ports where bright sunlight will reflect off the oil with a distinctive shimmer, distinguishing it from the surrounding water. GNSS waypoints for cleaning paths can therefore be plotted based on visual estimates made from a ship or the quayside. While positioning the containers and absorbers at approximately surface level helps to catch as much oil as possible, rarely will a USV capture all the fluid in a single pass, as the current will carry stray droplets of oil over and under the containers, or thread them through the limited spaces between the containers and absorbers. So in most hydrocarbon-focused operations, it will make repeated passes over an area to give assurance that all the chemicals have been collected and that the water is clean. Also, while the Cleaner is moving, an FPV camera installed on the front will stream live video back to the operator’s GCS, from which they can track that the USV is successfully scooping up oil and litter. Between the two forms of pollutant, oil clean-ups bear closer FPV monitoring as the spills are more sporadic, accidentdriven occurrences, whereas litter buildups are more predictable. “Marina Barcelona 92 for instance, a major marina for superyachts, is committed to sustainability and innovation in environmental matters, and uses at least one of our Cleaners for 2-3 hours a day to keep the water clean for its clients,” Barchino says. As mentioned, GPA Seabots can deploy multiple USVs at once if the situation demands it. This tends to happen more often in larger ports, such as the commercial harbours or luxury marinas found in Spain where spill quantities or the urgency of containment can be greater. In addition to two or more USVs moving in a swathe over a patch of oil, its containment can be performed in which the USVs either encircle a spill and enclose their absorbers around it, or move in a corkscrew pattern around it, to minimise the chances of any chemical droplets being pushed outside a given area and potentially towards bystanders. “Also, the FPV camera is useful for routine surveys, such as visually inspecting underneath bridges or drains, where regular boats cannot go,” Barchino says. “It’s also valued by our operators because they don’t lose visual tracking of where the USV is, even when it ‘disappears’ between boats. “Many port authorities have stressed to us that they always want to be able to clean every feasible inch of their ports, even between all the moored boats. That’s hard for human cleaners, but they don’t ever want to lose track of where the USV is, so getting a constant video feed, over 2.4 GHz wi-fi, is key.” He adds that such customers similarly want the USVs to survey every last nook and cranny of their harbours, even when using multi-beam echo sounders that don’t need to go right up to a quay’s walls. Notably, survey sensors and cleaning equipment can be installed together, with some configurations of the Cleaner having a water quality measuring sonde fitted in front of the litter basket. The most soughtafter data are typically measurements of conductivity, temperature and salinity in harbour waters. “But surveys are just as important as December/January 2024 | Uncrewed Systems Technology After the litter basket is deemed full by a weight sensor, the Cleaner returns to port and both litter and any oil can be put into special containers
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