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Two types of information service based on satellite data are available:<=
br>
=E2=80=A2 Routine monitoring of a defined area of interest for the occurre=
nce of oil slicks. In this case, the information provided includes a notifi=
cation of the occurrence of an oil pollution event, its location and extent=
. In addition, the locations of vessels and the metocean conditions around =
the slick can also be provided. Finally, by fusing the oil slick informatio=
n with AIS transponder information, potential polluters can also be identif=
ied
=E2=80=A2 Compilation of statistics on the occurrence of oil slicks in a d=
efined area. This provides a characterisation of the spatial variation in o=
il slicks based on historic data. Information can be
compiled on inter-annual and interseasonal variability
Typically satellite radar imagery with a spatial resolution of 30 =E2=80=
=93 150m is used for oil slick detection. This ensures the widest possible =
coverage for a reliable detection of an oil slick.
Due to constraints associated with the use of the service and the fact tha=
t large oil slicks move only as a result of forcing by environmental condit=
ions, a daily update frequency is usually sufficient.
This service is available world-wide although in some areas there may be a=
degradation of the information delivery time due to the lack of a suitably=
equipped ground station in the vicinity.
Detection of large oil slicks is almost 100% accurate. In some cases (e.g.=
accidents involving spillage of very heavy oils), the oil may float below =
the sea surface and be difficult to detect. In areas prone to sea ice forma=
tion, it may also be difficult to detect illicit discharges.
False alarms are an issue in oil slick detection. Naturally occurring surf=
actants such as algal blooms or natural seepage can create the same effect =
on the sea surface as an illicit discharge and be falsely reported as pollu=
tion. Similarly areas of low wind may appear similar to oil. For large slic=
ks, false alarms are quite rare when the image analysis is performed by an =
interpreter with appropriate experience of the region of interest. As for f=
isheries control, the issue of the restricted times of day at which radar s=
atellites pass over a given area of interest constrains the update times. A=
s most organisations use the satellite derived information to optimise depl=
oyment of airborne surveillance, it is often the case that only the morning=
acquisitions are used as many surveillance aircraft operate during dayligh=
t.
Satellite derived information provides an initial notification of the occu=
rrence of a pollution event within 20-30 minutes of the satellite passing o=
ver a given area. It also provides an analysis of the presence of potential=
polluters and an estimate of wind conditions.
National authorities use this in= formation to cue patrol aircraft to make an on-site inspection and also to = complement airborne surveillance in regions where airborne operations are m= ore difficult or costly. In addition, if an oil discharge is detected and a= possible source vessel identified on the basis of AIS data then the nation= al authority can request a P= ort Inspection at the next destination of this vessel. This represents an i= ncreased level of deterrence to ship masters against making illicit dischar= ges. All of these capabilities are fully operational within the European Maritime Safety Agency (EMSA) = CleanSeaNet system provided to EU Member States. This covers national water= s and adjacent high seas areas subject to international environmental prote= ction agreements. This gives rise to the following benefits:
=E2=80=A2 Optimisation of the deployment of conventional patrol assets. =
Authorities can be notified of areas identified as being clear of oil and a=
reas where possible oil slicks have been detected, enabling flight hours to=
be targeted on the areas where they make the most impact
=E2=80=A2 Extension of the surveillance coverage beyond the immediate vici=
nity of patrolling assets. Limited airborne surveillance can be complemente=
d by satellite overpasses, in particular for
areas far away from the aircraft base.
There are also benefits associated with offshore oil and gas production an=
d exploration for new reserves =E2=80=93 for example:
=E2=80=A2 Offshore oil and gas producers must ensure that an effective pol=
lution detection system is in place but this can be costly and limit intere=
st in more marginal basins. By using satellite based surveillance, costs ar=
e reduced, generating wider interest in operating licences for new producti=
on areas
=E2=80=A2 Seismic survey is time consuming and the survey vessel must be r=
efuelled every few days. If this is done in port, it results in increased o=
perations costs due to the associated down-time. Many operators request per=
mission to refuel at sea but there is a strong associated risk of significa=
nt harm to the marine environment from leakage. In addition, such a process=
requires the presence of a representative of the national pollution contro=
l authority. By using satellite based monitoring, even small amounts of lea=
kage can be detected and the requirement to transfer an observer to the ref=
uelling vessels is avoided. This represents significant cost savings for th=
e pollution control authority as well as requiring less time commitment fro=
m the monitoring personnel.
Finally satellite based detection of pollution from oil production= platforms and under-sea wrecks can also be used to cue airborne surveillan= ce. Sentinel-1 will provide routine coverage of most maritime areas world-w= ide, enabling cost effective pollution surveillance. When combined with nat= ional missions such as Radarsat 2/Radarsat Constellation, TerraSAR and Cosm= o, updates every 12 hours over most marine areas will be possible. Sentinel= -3 will provide the highest resolution ocean colour data enabling improved = characterisation of naturally occurring surfactants and reducing false alar= ms for oil slick reporting.
References:
ESA 2013, Earth Observation for Green Growth: An overview of European an= d Canadian Industrial Capability
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Monitor pollution at sea |
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coastal water quality |
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