The Atmospheric Effects of Precipitation through Energetic X-rays (AEPEX) CubeSat mission

Precipitation into the upper atmosphere is one of the primary loss mechanisms for radiation belt electrons, particularly during the decay phase following geomagnetic storm enhancements. These particles go on to impact the upper atmosphere through ionization, which leads to a chemical response that increases NOx and HOx and destroys ozone. Quantifying both the loss from the radiation belts and the impact on the atmosphere requires an accurate estimate of the flux, energy spectrum, and spatial and temporal scales of precipitation. However, such assessments are particularly difficult due to limitations of most measurement techniques.

The AEPEX CubeSat is designed to quantify these parameters of radiation belt precipitation by measuring the bremsstrahlung X-rays created during the precipitation process. AEPEX will image the X-ray fluxes produced by the atmosphere, providing measurements of spatial scales, along with the X-ray flux and spectrum. A solid-state energetic particle detector will measure the precipitating electron energy spectrum, which is used to constrain the inversion of X-ray fluxes to electron fluxes. We show in this talk and in Xu and Marshall [2019] that the combined particle and X-ray measurements can be used to accurately measure the precipitating electron flux and the atmospheric ionization response. We present the science goals of the AEPEX mission, the mission design, and the spacecraft and instrument designs.