SEP Warnings for the Moon and Mars

Arik Posner, NASA/HQ Heliophysics Division

Long-term goals of space exploration are a safe human return to the moon and travel to and from Mars. In particular, the problem of astronaut radiation exposure from cosmic rays and solar energetic particles (SEPs) at the moon and on the way to and from Mars needs to be addressed. The sudden occurrence of solar energetic particles in the inner heliosphere can, in extreme cases, lead to acute radiation sickness and related detrimental consequences. A solar energetic particle warning system can reduce radiation exposure and limit adverse effects by allowing astronauts sufficient time to temporarily move to a radiation shielded location in the spacecraft. One possible scenario providing the early warning to the explorers is the placement of a Relativistic Electron Alert System for Exploration (REleASE) at Earth-Sun L1 and Mars-Sun L1. This system would use the arrival of fast SEP electrons to forecast occurrence of high fluxes of harmful (but slower) solar energetic ions at their respective locations, and along significant stretches of the interplanetary magnetic field. While at times far from the human explorers, the REleASE system would exploit the Hohmann-Parker effect, as the explorers on Hohmann trajectories to and from Mars at all times stay rather well connected to either the vicinity of Earth or Mars via the Parker magnetic field in the heliosphere. This work investigates the relative timing of alert occurrence of particle escape signatures and the arrival of harmful ions at the spacecraft through data analysis and realistic SEP event modeling applicable to lunar stays and all stages of a round-trip mission to Mars.