Airborne Oil Pollution Patrol 2
- Long-range Oil Spill Detection with Radar -
Scenario
With good luck, the pilot of a surveillance aircraft might find an oil spill along the flight track. But more often, this is not the case! Therefore, a sensor suitable to detect oil spills over long distances is needed. This sensor is the radar, i.e., the so-called Side-looking Airborne Radar or SLAR.
With its bar-shaped antenna fastened to the lower side of the aircraft - as seen in the image below -, the SLAR emits short microwave pulses which are directed to the water surface. Water is a good reflector of microwaves. Now, waves on the water surface make it possible that part of the radar pulses are reflected back to the aircraft and detected with the SLAR antenna. Oil on the water surface dampens waves, so that a flat water surface reflects the pulses away from the aircraft, just like a mirror, and reflected radar pulses are not detected with the antenna.

SLAR antenna

We are operators of oil spill detection instruments, underway aboard a surveillance aircraft and we have a close look at the image obtained with the SLAR on the screen of the mission computer. At once we observe the image below:

Image of the sea surface to the right of the aircraft, taken with the Side-looking Airborne Radar (SLAR). The aircraft track is parallel to the left edge of the image. Image dimensions on the sea surface are approx. 3000 m along-track, 4000 m across-track.
How can we interpret this image? Waves on the water surface yield echoes of the radar pulses, and the brightness of the white spots corresponds to the echo intensity. Areas having a flat water surface do not cause any radar echo and are thus shown in black colour.
Questions
1.	How do you interpret the black and white areas in the SLAR image? Where would you expect to find an oil slick in the image? 
2.	Can you identify spill areas with thin or thick oil film thickness?
3.	What are the advantages and limitations of SLAR for oil spill detection?
4.	Can you recommend SLAR
a) to measure thin oil films caused by controlled (and mostly illegal) discharges of small oil quantities?
b) to distinguish thin oil films caused by controlled spillages from larger oil volumes caused by accidental discharges?