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and ice forecasts. The ice information that is collected by the 
Swedish Meteorological and Hydrological Institute (SMHI) and made 
available to the Ice-breaking Service and shipping was in the 
early 70-ties principally based on visual observations from shore- 
based observers, ice-breakers equipped with helicopters, merchant 
ships and satellite pictures. 
A modern surveillance system for the mapping of sea ice, however, 
can only be based on remote sensing techniques. In order for Sweden 
to acquire experience of her own and to assess the capability of 
remote sensing techniques for surveillance and mapping of sea ice, 
a field experiment (designated SEA ICE 75) was organized in inter- 
national cooperation in the Bay of Bothnia in March 1975. It was 
the first time such a comprehensive remote sensing experiment on 
sea ice was performed in Europe. 5 aircraft, 3 helicopters, 1 
ice-breaker, and about 50 scientists and technicians took part in 
the experiment. Data were also received from 2 satellites. 
The experiment was performed within a general cooperation between 
Sweden and Finland on winter navigation research. 
The following organizations took active part in SEA ICE 75, 
Rijkwaterstaat Meetkundige Dienst (the Netherlands): Side-Looking 
Airborne Radar (SLAR) installed in an aircraft, 
Helsinki University of Technology: Microwave radiometer and IR 
radiometer installed in a helicopter, 
University of Helsinki: Sonar for underwater ice profiling, 
Institute for Marine Research (Finland): Field measurements, 
NASA (USA): Satellite Landsat-2, 
National Land Survey of Sweden:Multispectral camera package and 
measuring camera installed in an aircraft, 
Swedish National Defence Research Institute, FOA,in cooperation 
with the Air Force and Navy: Forward-Looking Airborne Radar (FLAR) 
and aircraft, Omni-Directional Airborne Radar (ODAR) and helicopter, 
IR scanner and aircraft. Represented in the project managing group