The measurement flights of the exercise ARM13 were performed between June 24^th and 27^th, 2013. The exercise was organized by the National Emergency Operations Centre (NEOC) under coordination from 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 surveyed. As in previous years, the distinction between pressurized and boiling water reactor is clearly identified from the photon spectra. Additional areas to the north and south of the routine measurement area of KKG and to the north-west of KKM were added during this exercise to improve information on the background radiation level.
Measurements over the cities of Biel/Bienne and Thun were performed in the program to obtain radiation background values over Swiss cities. Further areas in the Kander valley were added to the program of the exercise. All of these areas showed background-level readings.
A military training area near Thun was used to test parameters of the data evaluation and to intercompare air with ground measurements. A flight line from Berne to Zurich was used to increase the coverage of Switzerland with radiological measurements.