Satellites can help provide near-real time monitoring and reporting of oil spills
Image credit: KSAT - Kongsberg Satellite Services image source
Oil spills can do serious damage to marine biology, the environment and also to coastal recreational areas. Detecting them and acting quickly to minimize their damage is therefore of vital importance to numerous stakeholders as well as to the public at large.
However, with oceans covering 71% of the globe and with thousands of vessels travelling different routes at any given time as well as numerous oil-rigs, keeping track of all potential areas for spills, as well as noticing and reporting them quickly is a big task.
Oil spills can cause significant damage to coastal environments, like what happened on February 2017 on the Bharathi Nagar Beach coastline in Chennai, India
Image source
However, there's a satellite app for that!
Satellites provide two unique benefits to solve the problem. First, and most obviously, they provide global coverage, allowing for every corner of the globe to be monitored. Indeed, for most regions of the oceans, there would be nothing else to observe and detect a spill outside of the ship itself. Second, the radar satellites using SAR (Synthetic Aperture Radar) are able to see through clouds. This means that a detection service can work at any place on Earth 24 hours per day regardless of weather conditions.
So how does it work?
Radar images do not display colours, however, they can show dark spots in an otherwise lighter environment. This is due to the fact that oil spills affect the scattering of electromagnetic waves which in turns changes the roughness of the sea surface. This tiny difference is noticed by the radar which is sensitive to millimetre changes. With a constellation of satellites frequently providing new data from any points on the ground, every day, for more than 20 years, prediction models has grown increasingly good at distinguishing oil spills from other dark spots in the oceans.
Detected oil spill in the Hong Kong coastal region from an ENVISAT ASAR image
image source
However, it can still be difficult to distinguish between other naturally occurring dark spots with similar characteristics from oil spills. Therefore, relying completely on the satellite images may help you find the oil spills, but it also finds a lot of extra false alarms.
Adding GPS data and SatCom
As it happens, it is mandatory for large trading vessels to use an Automatic Information System (AIS), the maritime equivalent of air traffic control that allows for autonomous tracking of ships. This system reports the position, moving direction and speed of the vessel and was initially built to prevent collisions. Since this data is obtained by the same coastal guards who need information about the occurrences of oil spills, this information is added to the oil spill monitoring system. If a dark spot resembling an oil spill is detected, it will quickly check if a vessel has recently passed over the same area, increasing the likelihood of it indeed being an oil spill.
This is now also done with satellites, as it was previously impossible to continuously track all ships all over the world due to the world's curvature meaning that ships travelling more than 72 kilometres apart would lose their connection. In fact, in my home country Norway we launched our own AIS satellites to provide better coverage in polar orbits. This has provided the coastal guards with complete communication links in the northern regions, and also helps make ship traffic for offshore oil platforms more secure.
Illustration of the AIS satellite network in Northern regions
image credit: ESA image source
Thus, the monitoring, detection and reporting of oil spills actually use all three main categories of satellites: Earth Observation (EO) satellites, global navigation satellite systems (GNSS) and communications satellites (SatCom). To me, it is a very cool example of technology and data integration to provide a unique tool that would be impossible to make with the same level of precision and continuity without the use of space-based assets.
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