Helicopter Time Domain EM (NuTEM)

Over the last several decades, electromagnetic prospecting using Helicopter platforms has proven to be a popular and beneficial survey approach. Consistent with this trend, NUVIA Dynamics has focused significant Research and Development efforts on developing a user-friendly and versatile electromagnetic system called NuTEM™. The system is intended for resource exploration, near surface geotechnical work and environmental studies.

With its dipole moment of up to 250,000 Am, the NuTEM™ system  is well suited for surveys with Depths of Investigation to 350 m (geology specific). NuTEM™ has a small foot-print and is robust – factors that have contributed to the adoption of NUVIA Dynamics’ system as one of the leading options on the market today.

NuTEM™ is a versatile state-of-the-art time-domain helicopter-borne Electromagnetic system. Weighing less than 350 kg on-hook, it features a powerful transmitter, a 3-component receiver, an integrated data acquisition system with survey navigation, and digital signal processing software package.

The system collects the 3-axis (X, Y and Z) response from the ground recorded in continuous mode. The collected data can be extracted into specified ON-TIME and OFF-TIME decay gates according to the aims of the project.

Components include a 3-axis receiver, current monitor, orientation re-calculation technique developed by NUVIA Dynamics, as well as transmitter platform positioning sensors. This gives a wide range of tools available for acquisition and treatment of the resulting data.

Unlike other commercial systems, the NuTEM™ is designed to be integrated on NUVIA Dynamics’ IMPAC-M platform – delivering a complete solution with ancillary magnetic and spectrometer results which are synchronized with the time domain system.

Image of Loop Transmitter System with Helicopter. Features on-board power generation and ease-of-flight for low noise and high signal quality

The system is a special Slingram configuration which provides results that are largely free of the transmitter dipole moment – remaining effects are then removed in software.

Features

NUVIA Dynamics’ NuTEM™ system features:

  • Powerful, compact transmitter with smooth-fly characteristics for low noise.
  • Three axis receiver with X, Y and Z components fully resolved and noise-free.
  • Digital data acquisition via the NUVIA Dynamics’ IMPAC system with full system control.
  • Lightweight for easy transport and operation with streamlined vertical lift.
  • Full wavelength recorded data for custom extraction and processing.
  • Windows configurable for different geologic targets.

Benefits – General

This powerful form of Electromagnetic prospecting delivers a number of unique benefits:

  • Enhanced geologic resolution for finely detailed conductors and structure.
  • Intermediate depth penetration suitable for many prospective exploration sites.
  • Light weight and low-noise profile in flight and in measurement of X, Y and Z responses.
  • Comprehensive software capabilities for data extraction and initial windowing.

Benefits – Rugged Terrain

  • Compact footprint for better defined anomaly positioning.
  • Stable, rigid platform for noise reduction in X, Y and Z data.
  • Optimal loop size for exploring in rugged terrain.

NuTEM™ System Description

This section describes the transmitter, receiver and detailed system specifications.

Transmitter

The transmitter delivers a half-sine wave pulse of a quarter duty cycle (25% pulse length) with a peak magnetic dipole moment to 380,000 NIA. The system can support two base frequencies, for example, 30 Hz and 90 Hz for a 60 Hz environment or 25 Hz and 75 Hz for 50 Hz environment. The transmitter current is fully monitored at all times.

Receiver

Nu-TEM features a powerful and compact three-axis receiver that records in X, Y and Z channels for effective mapping of anomalies (Z channel) as well as mapping of structure (X channel). Data are clean and well-behaved for transmitter off times.

System Characteristics

The NuTEM™ system has been fully tested at the Reed Mahaffey test site in northern Ontario – a well-known area flown by all major airborne contractors. NUVIA Dynamics’ flights in 2019 established new milestones for very high resolution (VHR) and mapping of individual conductors. It has also been flown for major mining companies.

Comparison of NuTEM™ Z channel responses for a range of windows.

The Latest in Proven Electromagnetic Surveys and Technology

NuTEM™ Specifications

Technical Specifications                       Description

Type                                                         NuTEM

Standard Survey Speed                         55 to 60 Knots

Sensor Configuration                            Slingram

Surface Area                                           55 sq m

Weight                                                     300 kg

Structure                                                 Rigid Loop with Aluminum Frame

Estimated Resistance                            15 mOhm

Transmitter Power                                Generation in Centre of Loop

Suspension                                             Single Point

Integrated Systems                               Magnetics (Radiometrics – Optional)

Aircraft Type                                           Bell 206 Ranger, MD 500, AS350 or Similar

Sampling Rate                                        90 kHz, Each Sample ~10 μs

Transmitter                                           

Description                                             4 Turn Nonagon

Diameter                                                 8.6 m

Current                                                    1000 A Peak

Dipole Moment                                      220,000 NIA

Waveform Type                                     Half Sine; Vertical Dipole

Pulse Length                                           25 % of Full Cycle

Base Frequency                                      25 / 75 Hz in 50 Hz Environment; 30 / 90 Hz in 60 Hz Environment

Waveform                                               On Time from 451.1 to 1655.4 Microseconds

Power Source                                         Onboard generator

DC Power Generation                           400 Hz 125VAC Helicopter Generation

Mean Ground Clearance                      30 m

Receiver                                                  

Axes                                                         X, Y and Z component measurements

Position                                                   Offset to TX

Diameter                                                 28.5 cm

Number of Turns                                   240 Turns on Each Component

Orientation                                             Z Axis

Preamplifier                                            3 Channel

Configuration                                         Offset to TX (Front and Above TX)

Sampling                                                 90 Hz

Time Gates                                              Configurable with text file – 52 gates

Measurements                                      dB/dT & integrated B field

Mean Ground Clearance                      60 m

Acquisition System                              

Type                                                         NUVIA Dynamics’ IMPAC

CPU                                                           I7 Generation 2 Quad Core

Operation Temperature                       Degrees Celsius (-35 to 45)

Standard Sampling Rate                       20 Hz

Magnetometer Counter                     

Magnetometer                                       NUVIA Dynamics’ MMS8

ADC inputs                                              0.707 V Peak to Peak – 2 Second Polarization

Magnetometer Inputs                          8 Inputs

Recording Rate                                       Up to 100 Hz

Analog to Digital Conversion               24 Bit

Noise Envelope                                      0.002 nT peak-to-peak and 0.1 to 1 Hz bandwidth

Base Station Magnetometer             

Type                                                         CS-3

Manufacturer                                         Scintrex

Range                                                       15,000 nT to 105,000 nT

Sensitivity Recording Rate                    0.0006 nT Root(Hz) RMS @ 1 Hz

GPS                                                          

Type                                                         Hemisphere R330

Differential Correction                          Real Time

Number of Satellites                             25+

Recording Rate                                       10 Hz

Temperature                                         

Type                                                         NUVIA Dynamics P-DES

Full Scale                                                 -20 to 85 Degrees C

Resolution                                               0.036 Degrees C

Recording Rate                                       1 Hz

Barometer                                             

Type                                                         NUVIA Dynamics P-DES

Full Scale                                                 0.1600 hPa

Temperature Compensated Range    10.90%

Accuracy                                                  +/-  0.25%

Resolution                                               0.39 hPa

Recording Rate                                       1 Hz

Radar Altimeter                                    

Type                                                         FreeFlight Systems’ RA-4000 mounted on aircraft

Operating Range                                    0 to 2500 feet

Accuracy (0 to 100 ft)                            3%

Accuracy (100 to 500 ft)                       +/- 3%

Accuracy (500 to 2500 ft)                     +/- 5%

Recording Rate                                       1 Hz

Laser Altimeter                                     

Type                                                         LDM302A

Range                                                       0.5 m to 200 m for low reflectance targets; otherwise up to 3 km

Resolution                                               1 mm

Recording Rate                                       1 Hz

Humidity                                                

Full Scale                                                 0 to 100%

Temperature Compensated Range    10.90%

Accuracy                                                  +/- 1.7% RH

Resolution                                               0.04%

Operating Temperature                       -40 to 125 Degrees C

Unit of Measure                                     %

Software                                                

Data Acquisition                                    NuTEM™ Console

Survey Control & Data Storage           NUVIA Dynamics’ IMPAC Data Acquisition Unit

Windowing & TX Loop Removal          EMDATAView (proprietary)

Processing and Display                         Geosoft

Examples and Contacts

 See this video of our P-THEM system test flight- 2013

The results of test and demonstration flights are being presented yearly at different international conferences and conventions, including AGU, SAGEEP, KEGS and others.

For detailed information on NuTEM™ products or survey solutions, please email info@nuvia-dynamics.com.

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