The development of the airborne multi-sensor system at the Chair of Raw Material and Natural Resource Management started in 2012 . The main motivation was the need for an affordable and flexible airborne platform capable of acquiring high-quality geophysical data for resource exploration, geological mapping and environmental studies, especially in areas where ground-based surveys are limited or difficult to perform.

After evaluating different carrier platforms, an ultralight fixed-wing aircraft was selected. The VIRUS SW 100, a full-composite aircraft manufactured by Pipistrel, was chosen due to its low magnetic noise, good flight stability, low minimum flight speed and favorable operating costs. An important aspect of the development was that the aircraft was modified during construction in close cooperation with the manufacturer, allowing to be specifically built as a platform for geophysical measurements.

Several structural and technical modifications were implemented, including reinforcements for sensor installations at the wing tips, under the wings and at the tail, dedicated mounting points in the fuselage for geophysical instruments, optimized cable routing and a low-noise power supply. The system was designed as a modular platform, enabling different sensor configurations depending on the survey objectives.

Following its assembly, the airborne system was tested and validated during dedicated test flights. R. Wackerle, of Intrepid, Namibia concluded: The aircraft can be regarded as completely ‘demagnetized’ resulting in magnetic noise levels well below industry standard. The magnetic compensation is done in real time by the DAS (ICCS) and worked well in the test survey. The residual heading effect after compensation is within industry standard. The radiometric data acquisition system internally records 1024 channels from 0 to 3 MeV, but outputs a raw 256 channel spectrum to the DAS. Energy calibration is done in post-processing mode using the Gamman software by Medusa Systems and results in very stable peak positions. The thorium peak resolution of the system is of industry standard. The small volume of the scintillation crystal does result in a higher statistical noise when compared to standard 32 litre NaI crystals. However, the full spectral processing of the recorded data by a Monte Carlo based spectral modelling technique yields results that compare well with those of the (much heavier) 16 litre crystals: The energy calibrated spectra are corrected for aircraft and cosmic background and reduced to HSTP. The spectra are then modelled using laboratory derived standard spectra for each of the required radioelements (including Radon) using the full spectral information which results in the ground concentrations of the radioelements