Open AccessDESMEX: A novel system development for semi-airborne electromagnetic exploration
Author(s) -
Michael Becken,
C. Nittinger,
Maria Smirnova,
A. Steuer,
Tina Martin,
Holger Petersen,
Uwe Meyer,
Wiebke Mörbe,
Pritam Yogeshwar,
B. Tezkan,
U. Matzander,
B. Friedrichs,
Raphael Rochlitz,
Thomas Günther,
Markus Schiffler,
R. Stolz
Publication year - 2020
Publication title -
geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.178
H-Index - 172
eISSN - 1942-2156
pISSN - 0016-8033
DOI - 10.1190/geo2019-0336.1
Subject(s) - magnetometer , acoustics , transmitter , electromagnetic coil , waveform , system of measurement , noise (video) , remote sensing , fluxgate compass , computer science , induction coil , electrical engineering , geology , magnetic field , physics , engineering , radar , telecommunications , channel (broadcasting) , quantum mechanics , astronomy , artificial intelligence , image (mathematics)
There is a clear demand to increase detection depths in the context of raw material exploration programs. Semi-airborne electromagnetic (semi-AEM) methods can address these demands by combining the advantages of powerful transmitters deployed on the ground with efficient helicopter-borne mapping of the magnetic field response in the air. The penetration depth can exceed those of classic airborne EM systems because low frequencies and large transmitter-receiver offsets can be realized in practice. A novel system has been developed that combines high-moment horizontal electric bipole transmitters on the ground with low-noise three-axis induction coil magnetometers, a three-axis fluxgate magnetometer, and a laser gyro inertial measurement unit integrated within a helicopter-towed airborne platform. The attitude data are used to correct the time series for motional noise and subsequently to rotate into an earth-fixed reference frame. In a second processing step, and as opposed to existing semi-AEM systems, we transform the data into the frequency domain and estimate the complex-valued transfer functions between the received magnetic field components and the synchronously recorded injection current by regression analysis. This approach is similar to the procedure used in controlled-source EM. For typical source bipole moments of 20–40 kAm and for rectangular current waveforms with a fundamental frequency of approximately 10 Hz, we can estimate reliable three-component (3C) transfer functions in the frequency range from 10 to 5000 Hz over a measurement area of [Formula: see text] for a single source installation. The system has the potential to be used for focused exploration of deep targets.