Overview of the EZIE (Electrojet Zeeman Imaging Explorer) Mission

EZIE, the Electrojet Zeeman Imaging Explorer, is a NASA three-Cubesat Heliophysics mission scheduled to launch in late 2024 or early 2025. It employs four downward and cross-track looking miniaturized radiometers on each of the 6U CubeSat, flying in a pearls-on-a-string managed formation, to measure, for the first time, the two-dimensional structure and the temporal evolution of the electrojets flowing at altitudes of ~100–130 km. The four identical radiometers simultaneously measure polarimetric radiances of the molecular oxygen thermal emission at 118 GHz and employs the Zeeman sensing technique to obtain the current-induced magnetic field vectors at ~80 km, an altitude region very close to the electrojet.  This measurement technique allows for the remote sensing of the meso-scale structure of the electrojets at four different cross-track locations simultaneously at altitudes notoriously difficult to measure in situ. The compact 118-GHz heterodyne spectropolarimeters leverage technologies demonstrated by NASA’s TEMPEST-D and CubeRRT missions and the CubeSat bus from RAVAN, CAT, TEMPEST-D, and CubeRRT. Differential drag maneuvers are used to manage satellite along-track temporal separation to within 2–10 minutes between adjacent satellite to record the electrojet temporal evolution without the need for on-board propulsion. The combination of the sensing technique, compact instrument and Cubesat technologies allow EZIE to cost-effectively obtain never-before “mesoscale” measurements needed to understand how the solar wind energies stored in the magnetosphere are transferred to the thermosphere and ionosphere.  In this paper, we will present an overview of the EZIE mission, its science objectives, the Zeeman sensing technique employed, and the measurement products to be provided.