A Merged Search-Coil and Fluxgate Magnetometer Data Product for Parker Solar Probe FIELDS

NASA's Parker Solar Probe (PSP) mission is currently investigating the local plasma environment of the inner heliosphere (<0.25 R-circle dot) using both in situ and remote sensing instrumentation. Connecting signatures of microphysical particle heating and acceleration processes to macroscale heliospheric structure requires sensitive measurements of electromagnetic fields over a large range of physical scales. The FIELDS instrument, which provides PSP with in situ measurements of electromagnetic fields of the inner heliosphere and corona, includes a set of three vector magnetometers: two fluxgate magnetometers (MAGs) and a single inductively coupled search-coil magnetometer (SCM). Together, the three FIELDS magnetometers enable measurements of the local magnetic field with a bandwidth ranging from DC to 1 MHz. This manuscript reports on the development of a merged data set combining SCM and MAG (SCaM) measurements, enabling a high fidelity data product with an optimal signal-to-noise ratio. On-ground characterization tests of complex instrumental responses and noise floors are discussed as well as application to the in-flight calibration of FIELDS data. The algorithm used on PSP/FIELDS to merge waveform observations from multiple sensors with optimal signal-to-noise characteristics is presented. In-flight analysis of calibrations and merging algorithm performance demonstrates a timing accuracy to well within the survey rate sample period of similar to 340 mu s. Key Points We develop a technique to merge search-coil and fluxgate magnetometer measurements In-flight analysis shows that calibrations are accurate to within 100 mu s