Lecture # 1 Understanding the Space Radiation Environment
Given the press coverage of the manned space program, most people are aware that the radiation environment in space is different than what we are exposed to here on Earth, and that it is an issue for long term manned space travel. Without the shielding effect of the overburden of the Earth's atmosphere and the additional (geomagnetic) latitude dependence of the Earth's magnetic field, astronauts and their spacecraft are exposed to three primary sources of radiation. First, they are exposed to the Galactic Cosmic Rays, which are modulated as they propagate into the Solar "heliosphere" from the interstellar environment to reach any of our current or planned manned missions. Second, our own Sun is a source of occasional outbursts of radiation that are sufficient to pose a threat. These Solar Particle Events are difficult to forecast more than hours in advance, if that, and vary considerably from event to event. Finally, in the immediate vicinity of the Earth, the Trapped Radiation in the Earths radiation belts can be a significant source of radiation dose depending on the orbital altitudes and trajectories. Finally, one has to consider the secondary radiation, or albedo that results from the radiation splash-back when the primary sources impact a nearby object when one is near such another object like the Earth's atmosphere, a planetary surface or the spacecraft itself. In order to predict the "risk" posed to astronauts, we must start by knowing the nature of the radiation environment itself.
