Helicopter-borne time-domain electromagnetic system CGG HELITEM registers the elements of electromagnetic field, which measure bedrock conductivity response through the transient method (TM, Time Domain EM). Transmitter dipole moment of 2,000,000 A m2 allows to reach 700 m depth at the sections of average conductivity.
The surveying with HELITEM can be performed at the speed of 130 km/h. The towed transmitting loop is placed at a cable end (the total length of the cable is about 70 m) and a three-component receiver together with the magnetometer quantum sensor are placed in a “bird” located in the middle of the towing cable.
EM field transmitter:
- number of coils in the transmitter loop: 4;
- dipole moment of 2,000,000 A m²;
- cable length: 70 m;
- forced signal: impulse bipolar polisine;
- impulse frequency: 30 Hz;
- impulse duration: 4 msec.
EM field receiver:
- sensor orientation: X, Y, Z;
- number of recorded intervals: 30;
- measurement of both B and dB/dt fields.