Impact of Realistic Detector Response and Azimuthal Drift on the Quantification of Energetic Electron Precipitation Using POES/MetOp

Abstract Quantifying energetic electron precipitation is essential for understanding ring current and radiation belt loss, as well as magnetosphere‐ionosphere‐atmosphere coupling. The count rate ratio between the 90° and 0° telescopes (CR 90 /CR 0 ) on POES/MetOp satellites is a commonly used proxy for precipitation and pitch‐angle diffusion rates (). Traditional interpretations assume nominal detector fields‐of‐view and neglect azimuthal drift. Using a comprehensive Drift‐Diffusion model, we quantify for the first time the combined effects of realistic detector angular responses, including significant out‐of‐field contributions, and azimuthal drift on the CR 90 /CR 0 versus relationship. Realistic responses cause this relationship to flatten as diffusion weakens, while azimuthal drift increases the CR 90 /CR 0 ratio, creating significant longitudinal and hemispheric dependencies. Neglecting these combined effects during slow diffusion leads to substantial overestimation of and precipitation flux, resulting in significantly overestimated ionospheric ionization rates. This study provides a more accurate framework for resolving and electron precipitation using low‐altitude satellite data.