Remote Sensing of Electron Precipitation Mechanisms Enabled by ELFIN Mission Operations and ADCS Design

Abstract

The Electron Loss and Fields INvestigation (ELFIN) mission comprising two 3U+ CubeSats was developed, built, and operated by several generations of undergraduate students at UCLA. The spin-stabilized CubeSats (spin-rate: 21 RPM) produced high-resolution measurements of precipitating, trapped, and backscattered fluxes of electrons and ions in the radiation belts. Launched in September 2018, ELFIN operated successfully until its deorbit just over four years later. At first, however, mission operations was very challenging and only tapped the full mission potential after a thorough redesign of the operations paradigm. This mid-mission adjustment yielded the higher data downlink volume necessary to acquire a comprehensive data set, therefore enabling ensemble studies with sufficient statistical significance. The new operational framework also led to additional improvements across the mission. Most notably, the Attitude Determination and Control System (ADCS) benefited from more reliable collections of magnetometer data for attitude determination, enabling knowledge and control to < 1^o. This allowed high pitch-angle resolution (especially within the loss cone) and high energy resolution spectrograms, both powerful diagnostics of radiation belt electron and ion precipitation. This paper highlights the scientific advancements made possible by ELFIN's efficient mission operations and ADCS design, unique for CubeSats, and emphasizes the role of electron precipitation measurements for future studies in magnetospheric, ionospheric, and atmospheric physics.