Magnetic polarization effects of temperature sensors and heaters in LISA Pathfinder

Temperature sensors and heaters belong in the diagnostics subsystem of the LISA Technology Package (LTP) on board LISA Pathfinder, the technology demonstrator for LISA. A number of these diagnostics items are placed at short distances from the LTP proof masses and are negative temperature coefficient (NTC) thermistors. By design, these devices have tiny amounts of ferromagnetic materials, which therefore constitute a potential source of disturbance to the performance of the LTP. In this paper we report on detailed magnetic characterization of the NTCs and use the data to evaluate their impact on the acceleration noise budget of the LTP. The effect is seen to be small if the NTCs are submitted to a demagnetization process before they are attached. Remagnetization is unlikely, as rather strong fields (approximately millitesla) are required to produce enough NTC magnetic polarization.