Space missions using magnetometers have been very successful. However, science missions now require higher levels of accuracy and stability in order to refine existing understanding and improve modeling. In most space missions that require high-accuracy vector measurement of magnetic fields, a separate scalar magnetometer must also be included in order to calibrate the vector measurements. The miniature laser magnetometer (MLM) addresses the need for a single, high-stability magnetometer instrument that provides both scalar and vector measurements for future space science needs while minimizing size, mass, and power.
The MLM eliminates the need for a triaxial fluxgate vector magnetometer and an independent scalar magnetometer usually required to correct for fluxgate drifts and offsets. The prototype MLM achieves a vector dynamic range of 75,000 nT with a sensitivity of
The MLM conceptual design includes three key innovations. The first is a new non-magnetic laser package that will allow the placement of the laser pump source near the helium cell sensing elements. The second innovation is the design of compact, nested, triaxial Braunbeck coils used in the vector measurements that reduces the coil size by a factor of two compared to existing Helmholtz coils with similar field-generation performance. The third innovation is a compact sensor design that reduces the sensor volume by a factor of six compared to MLM’s predecessor.
The MLM instrument design utilizes two distinct methods for performing scalar and vector measurements of magnetic fields. For scalar measurements, the MLM uses the magnetically driven spin precession (MSP) technique where a coil near the helium cell sensing element is driven with a signal oscillating at the Larmor frequency. The signals from three orthogonal cells are summed to obtain omnidirectional sensitivity. For vector measurements, the MLM uses the bias field nulling (BFN) technique where orthogonal coil sets around one cell are used to null the magnetic field. The magnetic vector components are then proportional to the current required to null the field in the cell.
This work was done by Robert Slocum and Andy Brown of Polatomic, Inc. for Goddard Space Flight Center. GSC-16894-1