Solar Cycles, Radiation Support for Manned Space Missions, and Expectations for International Space Station Construction

Since the planning for Apollo missions, radiation protection for manned space missions has included the monitoring and prediction of solar particle events in the near-earth environment. Experience since the Apollo missions provides a baseline for estimating the frequency and intensity of exposure to solar particle events in during the construction of the International Space Station (ISS). ISS construction will fall across the predicted sun-spot peak of solar cycle 23, which began in late 1996 and is expected to reach maximum in 2000 or 2001. Experience from recent solar cycles indicates that the construction coincides closely with the maximum phase of the occurrence of solar particle events extending from two to three years before the sunspot maximum to three to four years after maximum. Solar cycle 23 will see the use of new sophisticated methods for solar particle event monitoring and forecasting, including the use of new monitors of solar activity and monitoring of the solar wind. The new solar monitoring provides information on solar mass ejections that are now known to be important in the process of producing solar particle events. Monitoring of the solar wind provides information on the structure of the interplanetary magnetic field and shocks in the solar wind. These are now known to be important in moderating or even producing the most profuse solar particle events. This paper provides an estimation of the probability of solar particle events occurring during ISS construction periods and estimation of the intensity of these events. It will also provide a view of the procedures that will enable planning to minimize crew exposure to the events.