Aerial measurements in the environment with helicopters

This paper describes an airborne measuring system for nuclide specific measurements of soil contamination and for detecting sources of gamma radiation. The measuring device was jointly developed by the Federal Office for Radiation Protection and the Eurocopter Service, the former Henschel Aircraft Corporation, in close co-operation with the German Federal border Police operating the helicopters. The measuring device is installed in a helicopter of the type Aloutte II Astazou. Nuclide specific measurements of soil contamination are performed by employing a computerized semiconductor gamma ray spectrometer with a high purity Germanium (HPGe)-detector. At an altitude of 100 m soil contaminations of some kBq m-2 of 137Cs can be measured (measuring time of 60 s). For the detection of sources of gamma radiation, a 12 L NaI(Tl)-scintillation detector is used. At a flight path distance of 300 m and a 100 kmh-1 an area of approximately 30 km2 can be covered per hour, whereby gamma sources of an activity of some GBq are still detectable from an altitude of 100m. A satellite-navigation system (GPS) is used to determine the position of the helicopter. The altitude above ground is continuously measured by radar altimeter. The flight route is continuously measured by radar altimeter. The flight route is continuously recorded by a video system. The results of measurements at a highly contaminated region in the former Soviet Union, of an international intercomparison measuring campaign in Finland in 1995, and of measurements at mining and milling sites in Germany are reported. (author)