Summary of Working Paper No. 134-1999

I.2.4 “Practical Demonstration of Real-time RADARSAT SAR Data for Ice Navigation on the Northern sea Route”

By S. Sandven, Ø. Dalen, M. Lundhaug, and K. Kloster, Nansen Environmental and Remote Sensing Center, Bergen, Norway; V. Alexandrov and V. Melentyev, Nansen International Environmental and Remote Sensing Center, St.Petersburg, Russia; V. Smirnov, Arctic and Antarctic Research Institute, St.Petersburg, Russia; and N. Babich, Murmansk Shipping Company, Murmansk, Russia.

This project has demonstrated the practical use of RADARSAT data for ice navigation in the Northern Sea Route. This was first demonstrated in August - September 1997 onboard the nuclear icebreaker ‘Sovetsky Soyuz’, when she sailed through the Vilkitsky Strait and into the western part of the Laptev Sea. During the expedition RADARSAT, ERS-2 and SSM/I data were obtained and analyzed. The data were transmitted onboard the icebreaker in digital form via INMARSAT and used for the navigation support. Sea ice observations were obtained from the icebreaker and a helicopter for validation of the SAR sea ice signatures.

The first RADARSAT SAR images were obtained before ‘Sovetsky Soyuz’ left Murmansk, and were used for detailed ice mapping as part of the planning of the expedition. A RADARSAT ScanSAR image obtained 3-4 days before ‘Sovetsky Soyuz’ entered the ice area, was transmitted onboard the icebreaker. Because of the limitations imposed by INMARSAT communication system, the resolution of transmitted images was reduced to 500 by 500 m. Also SSM/I 85 GHz images and ice concentration maps were transmitted onboard the icebreaker and used for navigation in the Laptev Sea.

The image analysis showed that the main sea ice parameters, such as ice edge position, ice concentration and identification of large ice floes can be identified from RADARSAT SAR data. Sea ice bands in the open water can be also distinguished. Ice drift vectors and areas of convergence/divergence can be determined from successive images. The main problem is distinguishing between open water and new ice types (grease ice, nilas), because all the features have low backscatter during calm wind conditions. These areas could only be identified with help of in-situ data. Sea ice charts from obtained RADARSAT ScanSAR images have been prepared by the Arctic and Antarctic Research Institute. The areas with different sea ice concentrations were delineated and concentration values were automatically calculated.

Image transmission is the main bottleneck in using SAR data for ship routing in near real-time, because of the limitations imposed by INMARSAT. In the central part of the Laptev Sea and in the Central part of the Arctic Basin, satellite images cannot be received onboard because this is outside the range of INMARSAT.

In April-May 1998, a winter demonstration was carried out in the Kara Sea. In this period two icebreaker expeditions used RADARSAT and ERS SAR data to map the ice area between the Barents Sea and the Yenisey Gulf. These demonstrations showed that satellite SAR data can play an essential role both in operative and tactical ice navigation, especially during heavy ice conditions. The winter demonstrations were parts of two EU-funded projects, ICE ROUTES and ARCDEV.

SAR coverage of the whole Northern Sea Route with RADARSAT data is possible technically, but very expensive. It is therefore not realistic to use SAR data as exclusive data source for ice navigation A practical solution is to use a combination of SSM/I, ERS/RADARSAT, Okean, and Resurs/Meteor data.

For future operational ice monitoring in the NSR it is necessary to focus on the following problems:

Facilitate access of SAR data for Russian users. Today both organisational, financial and technical barriers make use of SAR data difficult for Russian users.

Improve the utilisation of Russian satellite data, which require improved data communication and financing.

A new SAR receiving station is needed in Siberia which can cover the whole Northern Sea Route.

Involvement from key end users (shipping companies, oil companies) to support a cost-efficient ice service for the Northern Sea Route.

Strengthen the hydrometeorological data acquisition and distribution necessary to provide ice analysis and forecasts.

Support new Russian satellites which can contribute to ice monitoring.