Airborne Gravity and Gradiometry Surveys

Airborne magnetic and gravimetric sensors are key geophysical tools in mining. They allow the mapping of vast areas from airplanes, helicopters, or drones to identify mineral deposits based on magnetism and density anomalies.

The main sensors and technologies used in mineral exploration are detailed below:

Sensors for Airborne Magnetometry

These sensors measure variations in the magnetic susceptibility of subsurface rocks to detect faults, geological structures, and mineralized bodies (especially iron, nickel, and gold).

• Optical Pumping Magnetometers (OPM): Highly sensitive scalar sensors based on potassium, cesium, or rubidium vapors. They are the industry standard for regional mapping.

• Fluxgate Magnetometers: Vector sensors that measure both the direction and magnitude of the magnetic field, making them ideal for lightweight systems.

• SQUID Sensors: Superconducting Quantum Interference Devices that offer the highest resolution available to map extremely subtle anomalies.

• Drone-Integrated Systems: Miniaturized and ultra-lightweight sensors operated on platforms for low-cost local prospecting and target detection.

Sensors for Airborne Gravimetry

These instruments measure tiny changes in gravitational acceleration caused by density differences in the subsoil. They are ideal for locating massive sulfide deposits, coal, or iron formations.

• Airborne Gravity Gradiometers (AGG): They measure the spatial gradient of gravity. By calculating the difference between multiple internal accelerometers, they effectively eliminate noise caused by turbulence and aircraft movement.

• Full Tensor Gradiometers (FTG): They record all components of the gravitational curvature tensor, providing high-definition 3D images of the geometry of mineralized bodies.

• Airborne Relative Gravimeters: Instruments that measure gravity variations relative to a ground control point. They require millimeter-precision GPS/GNSS positioning systems to correct for flight accelerations.

Installation Methods on Aircraft

• Stinger Installation: The sensor is placed on a rigid boom extended from the tail or nose of the airplane or helicopter to keep it away from magnetic interference caused by the engines.

• Wingtip Pods: A configuration of multiple magnetometers at the wingtips to directly measure horizontal magnetic gradients.

• Towed Systems ("Bird"): The sensor is suspended by a cable up to 90 meters long beneath a helicopter to fully isolate it from the aircraft's electronic noise.