Deperming is required for removal of the permanent signatures or generation of well-defined permanent signatures of naval vessels after ascertaining magnetic signature levels. The intended facility can also be used to calibrate the on-board Degaussing system, to ensure minimal signatures.
Deperming aims for a zero horizontal permanent magnetic moment and a predefined vertical permanent magnetic moment adapted to the ships location. The simulation coil system is used to compensate the local horizontal magnetic field component so the result of the deperming procedure is a zero horizontal permanent magnetic moment of the ship. The vertical simulation field is set such that the resulting ship magnetic moment is in total zero at the predefined ship’s location, the vertical permanent magnetic moment of the ship is than equal to the vertical induced moment of the ship.
Before and after the ship’s degaussing, the total magnetic moment including induced and permanent component are measured. The longitudinal magnetic moments can be obtained from two measurements with ships orientation in opposite directions in the South North and East-West direction. The value of the resulting magnetic moment is a measure for the quality of the accomplished deperming process.