A radar image alone visualises only a smoothening of 
the capillary waves of the sea surface by showing a dark 
feature. Fig. 1 gives an example of the same confirmed 
oil spill that is shown once by satellite-based SAR (left, 
ENVISAT-ASAR (ESA, EMSA 2008)) and once 
observed by air-based SLAR (right, three hours later, 
BfG, Central Command for Maritime Emergencies 
(CCME), 2008). 
® BfG, 
© ESA CCME 
Figure 2. Confirmed oil pollution in radar data. The 
same spill is shown once by satellite-based SAR (left: 
ENl'ISA T-ASAR (ESA. EMSA 2008» and once 
obsereved by air-based SLAR (right, three hours later. 
BfG. CCME 2008). 
Such dark features can not only be caused by mineral oil 
but there are various reasons for look-alikes as e.g. fish 
or vegetable oil, other pollutions and even natural 
phenomena such as algae blooms as well as upwelling 
or low wind areas. 
For the satellite services, the analysts use additional 
information such as wind velocity (model or SAR wind) 
to support the classification of the detected features, i.e. 
for the decision if the feature is reported as a possible 
oil spill and which detection probability is assigned to 
the feature. Further information received visually from 
the image as e.g. the specific shape, surrounding and the 
edges of the feature are major criteria for the 
classification. Ref [8] summaries the ongoing discussion 
on classification systems from a European perspective. 
The users of the satellite services need to know if the 
reported feature is really a pollution caused by mineral 
oil. This is important for the decision if follow-up 
measures have to be taken, e.g. if a reported feature 
needs to be combated or not. Therefore the users require 
as much information as possible about the type and 
amount of oil. Due to physics, this information can not 
be delivered by analysis of a radar image alone. 
Therefore, most users of the CSN-service deploy 
surveillance aircraft or ship for a further investigation of 
the scene and in order to confirm the presence of an oil 
spill based on the satellite oil spill alert. 
Moreover, aircraft allow for an additional, more flexible 
and high resolution routine surveillance as well as a 
pollution combating assistance - though aerial 
surveillance can make good use of satellite services as a 
first alert tool over areas of up to 400x400 km 2 . Fig. 4 
shows the flow of information from the satellite via the 
receiving station to the satellite image analysts. The 
analysts send out alerts by e-mail, phone or text 
message to the users who can decide about their follow 
up decisions, as e.g. as a first step to launch their aircraft 
for check-up. Additional information as e.g. sliapefiles 
of polygons around possible pollutions are available for 
visualisation or download at the CSN-webportal. 
Figure 3. Acquisition of satellite data (adopted from 
[9J> 
In Germany, two aircraft of the type Domier 228 are the 
main component of the oil pollution surveillance. They 
are flown and maintained by the Naval Air Wing 3 
“Graf Zeppelin" on behalf of the CCME and the 
German Federal Ministry of Transport, Building and 
Urban Development (BMVBS). These aircraft are 
equipped with a multi-sensor mission system including 
as a far range sensor a Side-Looking Airborne RADAR, 
SLAR, allowing for a detection of possible pollutions 
up to 30km and either side of the aircraft. The 
equipment is accomplished by a set of near-range 
sensors with a range of up to 250m on each side 
including a Infrared/ultraviolet seamier, a 3-channel 
microwave radiometer (MWR) and a laser fluorescence 
seamier as well as various photo- and video- 
documentation tools. Together with the experience of 
the trained operators this sensor system allows for a 
qualitative and quantitative judgement of the observed 
features in the radar images (cf. also [10]). 
In case of the detection of a noteworthy oil pollution by 
means of remote sensing, oil spill drift model runs are 
started.