AP9AE9

AP9AE9, commonly written AP9/AE9, is a paired radiation belt model used to estimate the flux of energetic protons and electrons in Earth's radiation belts. It serves as a modern replacement for the older AP8/AE8 models and is widely used in spacecraft design to assess radiation exposure and shielding requirements for mission planning.

The model was developed by NASA and partner institutions to provide a data-driven, probabilistic description of the near-Earth radiation environment. It incorporates measurements from multiple missions, including CRRES and the Van Allen Probes, spanning different solar activity levels, and expresses results as flux distributions with selectable confidence levels to quantify uncertainty.

AP9AE9 outputs include electron and proton fluxes as functions of energy, L-shell, and geomagnetic activity. The model supports various energy channels and confidence percentiles, enabling customized assessments for specific orbits and mission durations. Access is provided through platforms such as SPENVIS and related space environment data services.

Limitations and usage notes: AP9AE9 is tailored to Earth orbit environments and is not validated for other planets or extreme solar conditions beyond the data used. Users should consider model updates and cross-validate with mission-specific measurements when possible.