Flight qualification of the MEM instruments for the EZIE mission

The Electrojet Zeeman Imaging Explorer (EZIE) is a three-satellite mission that images the magnetic fingerprint of intense electrical currents flowing in the Earth’s ionosphere. The multi-point measurements of these electrojets will provide closure to decades-old, and much debated, mysteries of the interaction between the Earth and the surrounding space. Each one of the three 6U CubeSats carries a microwave electrojet magnetogram (MEM) instrument which consists of four identical 118-GHz heterodyne spectropolarimeters. These MEM instruments were designed to meet the stringent mass, power and volume requirements of the CubeSat spacecraft. MEM instruments use the Zeeman splitting effect on the 118.75GHz oxygen absorption line to infer magnetic fields at ~80km altitude. These magnetic fields are used to calculate the local ionospheric electrical currents flowing at 100-130km altitude. The flight models of the instruments were built and tested in-house at JPL within 12 months. Each of the final instruments weighs 4.1kg, and operates with 20W of power. Despite the compact size and low power consumption the noise temperatures of the instruments are at 450K level and the measurement noise is less than 1.5K on the 49kHz polarimetric spectrometer system. The planned launch of the EZIE mission is in March 2025.