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Electromagnetics

UTS Geophysics, through its sister company Aeroquest Limited, conducts helicopter-borne electromagnetic surveys using both time-domain and frequency-domain technologies, to satisfy a variety of applications.

AeroTEM™

AeroTEM™ is a time domain (sometimes called transient) electromagnetic system operating on platforms ranging from 5 metres to 12 metres in diameter.  AeroTEM™ is designed to optimise depth of penetration and discrimination of target conductors.  AeroTEM™ leads the industry with a combination of resolution, conductance discrimination and geometric information.

AeroTEM™ System Specifications

Features

• Presently achieving depths of exploration twice that of traditional frequency-domain HEM, greater than 500 metres with the new AeroTEM IV system.
• Next generation systems will approach depth of exploration of fixed-wing AEM.
• Highly focused EM footprint provides outstanding delineation and characterization of subsurface conductors, superior to that provided by the much more expensive large-loop ground EM methods.
• System is highly portable. Can be readily dismantled and re-assembled for economical deployment to any geographic location.
• First helicopter-borne EM platform to provide the well-established benefits of time-domain EM exploration in rugged terrain.
• System symmetry about the vertical axis makes target responses immune to bird heading, thereby removing the confusing responses seen by other systems while climbing in rugged terrain.
• Ideal system configuration for flying in a "low and slow", tight line spacing survey mode for detailing known conductive targets.

IMPULSE™

ImpulseTM is a digital helicopter-borne frequency-domain electromagnetic system developed by Aeroquest and introduced in 1997. This innovative wideband system utilises a single computer-controlled, high-output transmitter driver to power individual horizontal coplanar and vertical coaxial transmitter coils, producing a total of six frequencies (three in each coil orientation).

Impulse differs significantly from conventional multi-frequency systems in that the conventional systems use three independent coils per frequency (e.g. 18 coils for a conventional six frequency system versus 6 coils for six frequencies with Impulse). As a result, the Impulse approach not only minimizes noise from coil interaction, but reduces the overall amount of drift. Impulse uses a larger diameter tubular coil platform (30" as opposed to the traditional 20"), permitting the system to generate larger dipole moments, thereby resulting in an improved signal-to-noise ratio, which quickly translates to better integrity of the measured in-phase and quadrature data and an improved depth of exploration.

Specifications

GEM™

The  is a completely digital, programmable HEM system that is capable of mapping resistivity at various depths. The current GEM-2A employs both horizontal coplanar and coaxial transmitter-receiver coil pairs, which operate at multiple, simultaneous or stepping, user-specified frequencies. The system provides a broad bandwidth (to 96 kHz) and a high dynamic range (24-bit A/D conversion) at a 30 Hz sampling rate. Each coil pair simultaneously transmits and receives five to seven frequencies for a typical survey..

The transmitter power for the GEM-2A system has been increased. The physical size of the transmitter for the horizontal coplanar coil has increased by a factor of 2.5 and the coaxial transmitter coil has increased by a factor of 4. The resultant increase in moment is more pronounced at higher frequencies. The increases in transmitter moment improves sensor performance and the signal-to-noise ratio (SNR).

Specifications