üThe van Allen belts are regions above the Earth’s surface where the Earth’s magnetic field has trapped particles of solar wind. üAn unprotected astronaut would get a lethal dose if he stayed in the region long enough: the Apollo spacecraft passed through the belts in an hour or so. üThere wasn’t enough time to get a lethal dose – as well, most of the radiation was blocked by the hull. ü While in cis-lunar space, the radiation dose received by the Apollo astronauts was only a few rems.