An X-class solar flare on 31 March triggered a G2 geomagnetic storm watch, and NOAA's Space Weather Prediction Center extended a G1 watch through 2 April from a coronal hole high-speed stream 1. The TLI burn window falls within this active period. Once Orion crosses beyond Earth's magnetosphere, the crew loses the magnetic shielding that deflects most solar radiation. Six Hybrid Electronic Radiation Assessor sensors are deployed throughout the cabin, and each crew member carries a personal dosimeter. Baseline exposure for the ten-day mission is approximately 5% of an astronaut's career radiation limit, roughly equivalent to 50 chest X-rays. This mission coincides with solar maximum, the peak of the Sun's 11-year activity cycle. Apollo 17 in 1972 was the last crewed flight beyond low Earth orbit, and no crewed vehicle has tested radiation exposure models under solar maximum conditions since.
Solar Flare Creates Radiation Risk During Moon Burn Window
An X-class flare on 31 March and a G1 geomagnetic watch through today coincide with the TLI decision window.
This is the first deep-space crewed flight during solar maximum since Apollo.
Deep Analysis
The Sun goes through an 11-year cycle of activity. Right now it is near the peak of that cycle, called solar maximum, which means it is producing more flares and charged particle storms than usual. On 31 March, it produced an X-class flare, the most powerful category. This sends a wave of radiation toward Earth and any spacecraft in its path. Earth's magnetic field protects us on the ground. The ISS has some protection too because it stays inside that magnetic field. But once Orion crosses beyond the magnetosphere tonight, the crew is exposed to whatever the Sun is throwing. NASA has limits on how much radiation astronauts can receive across their career. This ten-day mission is estimated to use about 5% of that career limit even without a flare. The current conditions make that exposure somewhat higher. Flight controllers are watching it closely as part of the go/no-go decision.
Update #1 · Artemis II Commits to the Moon With Three Open Questions
