Cryogenic magnetic gradiometers for space applications

This article proposes the use of superconducting magnetic gradiometer, magnetometer sensors based on SQUID technology as sensors for space-borne magnetic investigations. The existing state of the art of such sensors is described. Estimates of their performance as space sensors is made; in particular, it is shown that they will provide magnetic data of improved sensitivity and accuracy over conventional magnetic sensors. It is also found that gradiometers of the sensitivity proposed here will aid in the analytic continuation of field data, will allow separation of magnetic field temporal variations from field changes due to flight past fixed magnetic sources, will provide the ability to make meaningful measurements of fixed anomalies on magnetospherically active days, and will allow increased spatial resolution of magnetic sources. The requirements for a high-performance space gradiometer sensor are described as well as current progress aimed at achieving such a sensor. Satellite system requirements are also addressed. Particular attention is given to magnetic noise sources in the sensor environment and to the problems associated with reducing this noise to the desired sensor noise levels.