The Vector Field Magnetometer (VFM) is Swarm's core instrument. It makes high-precision measurements of the magnitude and direction of the magnetic field, i.e. the field's vector.

The VFM uses the proven fluxgate magnetometer design. VFM features a wide-range, high performance ring core fluxgate magnetometer. The fluxgate sensor uses the nonlinearity of magnetisation properties for the high permeability of easily saturated ferromagnetic alloys to serve as an indicator for the local field strength.