I know. ‘Space radiation’. Space radiates, you know. Gotta love journalism.
The engineers KNEW they were going to a planet that had no magnetosphere. Moreover, you can test for this. You can actually create a lab environment where the vehicle has to perform under these conditions, and for extended lengths of time.
I’ve been studying the correlation between planetoids with magnetic fields and the observation of lightning on the planetoids.
“Space radiation” is the correct term, though sometimes you see “space weather”, to describe the particle environment.
A program used to estimate rad effects is called SpaceRad, after Space Radiation.