NOL vector airborne magnetometer type 2A

The NOL vector airborne magnetometer type 2A (VAM-2A) measures the direction and intensity of the Earth's magnetic field from aircraft. Like the earlier type 1A, it continuously records the total intensity of the field and the magnitudes of a number of angles which specify its direction, but the 2A can be used in all latitudes and requires fewer steps in the reduction of results. Electronic circuits are used to average continuously the always varying angular magnitudes over predetermined intervals of time so as to minimize errors arising from the deflection of the pendulously suspended magnetometer mechanism by accelerations of the aircraft. The total-field measuring system of the magnetometer has a temperature coefficient of about 0.5 γ/°C. Drift due to causes other than temperature change is about one gamma in 12 hr. Magnetic compensation virtually eliminates the necessity for correcting the data for the field of the aircraft. In a region where the angle of dip is about 60°, F, H, Z, I, and D are measured under average conditions with estimated probable errors of 15, 40, and 30 γ and three and five minutes of arc, respectively.