Norway, one of the world's leading producers of offshore crude oil has been compelled to develop sophisticated procedures for identifying and tracking oil slicks. Every year approximately 400 illegal oil spills are observed off the coast of Norway, which pose a constant threat to the country's coastal fisheries and extensive shorelines. Of these spills, 90% are under 1000 cubic metres in size, and as many as five to ten require organized containment and cleanup operations. Using satellite SAR and surveillance aircraft is one the most promising methods used by Norway in its oil spill management efforts.

Since 1981 Norway has used aircraft to patrol its 48,000 kilometres of shoreline and vast ocean areas to search for oil spills. Poor weather, light conditions and the high cost of operations over large areas limits the use of traditional airborne surveillance. "In Norway, a combined use of aircraft and satellite SAR is the most cost-effective choice for monitoring open seas, due to the year-round clouds and half-year of darkness," said Jan Petter Pedersen, director of marketing at Tromsø Satellite Station (TSS). Another challenge is the necessity of near-real time data for effective spill management. Airborne surveillance can provide this information but the general area of the spill must still be determined, a problem that proved difficult for traditional aircraft surveillance techniques.

As early as 1991 ERS-1 imagery was demonstrating the capabilities of satellite SAR to locate and monitor oil spills in Norway's water. Under a program to develop effective detection techniques, TSS was asked to provide coordinates of possible oil spills to the Norwegian Pollution Control Authority (SFT). A system was developed that allowed ERS-1 SAR image data to be generated within 10 minutes of reception by the TSS satellite station. By 1995, a more advanced system had been developed that allowed images to be easily transferred from TSS using standard e-mail. This advancement allowed the system to become partially operational in the spill detection process.

Oil spill service concept model, from reception and analysis of data at TSS,
through early warning alert and aircraft operations by SFT.

With the launch of RADARSAT in late 1995, and the implementation of RADARSAT SAR data, the system to became even more effective. "RADARSAT offers improved spatial and temporal coverage. It provides an important data source to bring the project another step closer to operational status," said Pedersen. ERS-1's single setting of 23 degree inclination and 100 metre swath had been adequate for detecting oil spills. However, RADARSAT's flexible viewing geometry, including multiple beam modes, allowed TSS researchers to determine the best possible combination of resolution and angle to be used in detecting oil spills. They found that the ScanSAR Narrow beam, with its coverage of 300x300 kilometre and resolution of 50 metres was capable of indicating spills. The major advantage of this beam is its ability to cover vast areas with single passes and provide a better cost per kilometre coverage. Norway's latitude also allows at least partial coverage of the area to be provided by ScanSAR nearly once a day. The ability to acquire images on a daily basis and monitor an oil spill had been greatly improved.

Verification of slicks that are detected on SAR images is still provided by aircraft equipped with Side-Looking Airborne Radar (SLAR). "We use satellite-based SAR data as a daily planning tool for aerial surveillance missions. Our dedicated Merlin Fairchild IIIB aircraft is guided by possible oil spills in SAR images," said Jørn Harald Anderson, a SFT senior executive officer. Efforts are also made by SFT to coordinate satellite passes with aircraft flight plans for the day to avoid possible overlapping coverage. "Satellite SAR data is particularly useful when possible oil spills are not observed at remote oil platform locations. This "no pollution" confirmation by satellite allows us to re-allocate flight time to areas not covered by the satellite," said Anderson.

A possible oil spill, dark linear features, in the Baltic Sea
can be seen in this October 19, 1996 RADARSAT ScanSAR Narrow image.

The increase in coverage and accuracy provided by RADARSAT represents a potential for customers, such as SFT, to be more effective in monitoring the vast area off Norway's coast.

Jan Petter Pedersen, Kongsberg Satellite Services, N-9005 Tromsø, Norway, Telephone: 47 77 68 4817, Fax: 47 77 65 7868, E-mail: janp@tss.no

References
Corbley, Kevin, May 1997, "Norway Enhances Oil Spill Detection with RADARSAT", EOM, Vol. 6, Number 5, Pg. 22-26.

Credits
Information used in this profile was extracted from an article which originally appeared in the May 1997 issue of EOM. Contact EOM at eomaged@aol.com for subscription information.

RADARSAT data copyright Canadian Space Agency/Agence spatiale canadienne 1996. Received by the Canada Centre for Remote Sensing. Processed and distributed by MDA Corporation. Imagery enhancement and interpretation by CCRS.