The Electric Field Instrument (EFI) for the TRACERS Mission.

The Electric Field Instrument (EFI) for the NASA Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) mission provides measurements of the electric field from DC to nearly 10 MHz on two closely-spaced spacecraft in low Earth orbit passing through the terrestrial cusp region. As measured by EFI, the plasma convection fields, ULF and ELF fluctuations, and natural HF emissions provide key measurements of plasma flow, plasma waves, and plasma density that support all three science objectives of the TRACERS mission. Here, we describe the mechanical and electrical design of the EFI, the data products it produces, and the concept of its on-orbit operations.