The measurement flights of the exercise ARM11 were performed between September 19^th and 22^nd under the direction of G. Scharding of the National Emergency Operations Centre (NEOC) and coordination by the Expert Group for Aeroradiometrics (FAR).
According to the alternating schedule of the annual ARM exercises, the environs of the nuclear power plants Gösgen (KKG) and Mühleberg (KKM) were inspected. No elevated radioactivity was detected in the environs of KKG and KKM.
The measurements over tunnel portals and excavated rock deposits of the New Rail Link through the Alps (NRLA) construction yielded no indication of anomalous radiological data due to the project.
Areas measured on behalf of the Federal Office for Public Health (FOPH) depicted no unusual activity concentrations.
At some of the sites, the difference of removal of ¹³⁷Cs deposited by the Chernobyl accident between paved and forested areas could be observed. A comparison at some sites to measurements performed nearly 20 years ago yielded ¹³⁷Cs activity concentrations slightly lower than would be expected from radioactive decay alone. Elevated activity concentrations of natural radionuclides at some of the sites could be traced to the underlying geological structure.
An exercise together with emergency responders of Canton Ticino on an area of 100 m x 150 m demonstrated the limitations in spatial resolution of aeroradiometric measurements. If the position of radioactive sources is known with an uncertainty smaller than the field of view of the aeroradiometric detector, the deployment of the aeroradiometry system cannot render additional spatial information of the source locations.