Design of OSE and OSSE for Earth’s radiation belts

Earth’s Van Allen radiation belts, located in near-Earth space, are comprised of very energetic electrons and protons.  However, the origins of these particles are from regimes of significantly lower energies.  Within Earth’s magnetosphere is a natural particle accelerator capable of energizing particles such that they can be harmful to space-based assets and potentially lethal to humans in space.  Reconstructing, predicting, and forecasting the radiation belt content is of critical importance to ensure safe activity in near-Earth space.  However, due to large spatial scales and poor sampling coverage, radiation belt dynamics continue to be widely investigated and are well suited for data assimilation methods.  The 3D Versatile Electron Radiation Belt code (VERB 3-D) is a global, three-dimensional data assimilative code to reconstruct the radiation belt environment.  The code ingests sparse observations and combines them with a 3D quasi-linear diffusion model to reconstruct the global electron environment.  Most recently, this model has been used to create an Observing System Simulation Experiment (OSSE), in which a synthetic environment is created and treated as the “truth”.  The synthetic environment is sampled, with representational errors, and reconstructed using the numerical model.  Comparison between the reconstruction and “truth” allows for quantification of the model performance.  Iteration of model parameters provides insight towards the physical system, and also sets the foundation for an Observation System Experiment (OSE).  The OSE follows the same steps as the OSSE, but is applied to the real radiation belt environment using historical in-situ observations.  While the true environment is not known for the OSE, information derived from the OSSE bounds reconstruction results.  These modeling approaches are relatively new to the heliospheric field, but are proven to be necessary for spacecraft operation, mission planning, and risk mitigation.