RST Radar Systemtechnik Details Water Surface Monitoring Synthetic Aperture Radar

RST Radar Systemtechnik's Water Surface Monitoring SAR (WSMS) is an all-time, all-weather airborne imaging radar featuring small antenna and low output power for applications like the detection of oil spills on water surfaces and identification of polluting vessels. Oil spills on sea surfaces are clearly visible in radar images due to their characteristics of significantly changing the reflectivity of water surfaces. The SAR imaging modes are

• Water Surface Measurement (Oil Detection Mode; ODM); and
• Full Resolution (Ship Detection Mode; SDM).

WSMS Mission Scenario (All illustrations: RST Radartechnik)

The SDM is a Single-Look Full Resolution mode and, hence, it is also well applicable for over-land operation. The major areas of application are:

• Sea border control and coastal monitoring;
• Monitoring of ship movements in coastal regions;
• Observation, prevention and detection of water pollution;
• Recognition of potential polluters (ship detection);
• Minimising oil pollutions and other sea pollution due to an early detection and provision of information required for performing effective counter measures;
• Enabling a more economic observation of huge sea areas and shipping routes;
• Land monitoring against smuggel and illegal immigration;
• Land monitoring for disaster management; and
• Change detection across borders.

The characteristics of the sensor are:

• Oil detection spatial resolution: 30x30m;
• Ship detection spatial resolution: 5x5m;
• Swath width: 2x40km (40km to the left and 40km to the right);
• WSMS antenna length: 76cm;
• Radio Frequency (RF) output power: 80W;
• Integration into smaller aircrafts possible;
• No risk/danger for pilots, operators and other people
• ITAR-free system;
• Nominal flight altitude: 300-3,000m (higher altitudes possible with slight degradations of SNR);
• Radar Frequency: X-band
• Operation during day and night, through clouds, fog, rain;
• On-board real-time SAR processing; and
• Image delivery in intervals of approx. three seconds.

The following options are available:

• SMGV on-board computer for Sensor Management, Geo-coding and Image Visualisation to be used for autonomous operation of the WSMS
• POSP off-line precision SAR processor (including geo-coding) to be used on PCs on ground for generation of high performance images.

System Configuration

The configuration of the WSMS consists of a SAR Electronics Unit, a SAR Digital Unit, and two SAR antennas (Double Side Operation). The WSMS is a SAR sensor that can be integrated into a multi-sensor observation suite. In this case, the WSMS delivers a SAR image burst approximately every three seconds on-board. Co-registration and data fusion is to be done in the suite computer outside of the WSMS sensor. In case of the WSMS as an independent sensor, the functions “Display“, “Operator Control Panel” & “Image/Raw-Data Storage” are offered with a second on-board computer including display and keyboard (SMGV). A Precision Off-line SAR Processor (POSP) for operation in the ground station is also offered as an option. The POSP provides SAR images of highest quality, where the Real-Time On-board SAR Processor is optimised for output speed.

The SAR Electronics Unit and the on-board computers, as well as the SMGV (if this option was selected) are to be integrated into an on-board rack. The antennas have to be installed outside of the airplane. The positions of the antennas have to be confirmed by RST in order to guarantee an undisturbed functioning of the WSMS. Two high-performance RF cables for connection of the radar unit with the antennas are delivered with a length defined by the customer. The length should not exceed 2m each.

Oil Detection Mode

An example of an ODM image shows the reflections of the ocean surface. Strong reflections from targets like ships or islands (in saturation) are shown up in white. Dark areas are either flooded land or polluted sea surface. The dark areas in the upper-left quarter are such flooded islands (identified by overlay the SAR image on maps), while the dark area to the right side might be pollution. The yellow rectangular area indicates the size of the image that is output approx. every three seconds. The dark horizontal stripes are residual errors after aircraft movement corrections in real-time. POSP is correcting these errors.

Oil detection mode

Ship Detection Mode

The overall dimensions of ships can be measured with 5m resolutions in SDM and ships can be classified by this information. Operating SDM over land can also provide important information. The resolution allows detection of land structures, border line contours, buildings, streets, and more. Wind generators can be identified by their point target shape and by their typically appearance in a row or in several parallel rows. Power lines can also be identified.

Ship return in Ship Detection Mode

Extraction from a land application image in full resolution mode

Geo-Coding

Geo-coding is required, when the SAR image is to be overlaid with a map. This can be done with the On-board Real-Time SAR Image when the SVGV Option was selected or in context with the POSP function off-line.

Map overlay of geo-coded SAR images