The New 4-Frequency Airborne EM System of JAC

Geological Survey of Finland (GTK) and British Geological Survey (BGS) have jointly (JAC) constructed a new, 4-frequency EM unit installed in a fixed-wing aircraft. The system follows the technique of the previous dual frequency unit of GTK. The frequence range is now from 0,9 to 25 kHz. The four separate coils are installed inside the pods situated at the wing-tips, the separation between transmitter and receiver coils being 21.4 m. The system sensitivity is wide, covering well geological and environmental targets, and the lowest frequency enhances the depth penetration. <br> <br>This paper describes the technical characteristics of the new system: specifications and noise level, and analyses the half space model responses. A test area survey was performed to find out the possibilities to utilise the data in interpretation. A 3D model based on systematic 1D inversion was compiled successfully. <br>