The Spacecraft Radiation Experiments

The radiation experiments 011 the T e l s t a r spacecraft were designed to measure the distribution in energy, position, and time of electrons and protons trapped in the earth's magnetic field in the Van Allen belts. Such particle distributions characterize the radiation environment of the satellite, and in addition help provide an understanding of the mechanisms that are responsible for injection of particles into the Van Allen belts and for loss of particles from the belts. The radiation experiments also measure directly the integral radiation damage effects 011 semiconductors. Only magnetically trapped particles are important for damage considerations on the satellite, and only they are being examined in the particle experiments. The direct effects of primary cosmic rays are negligible, as are also the effects of solar protons which stream into the earth's polar regions but do not reach the Telstar satellite's extremes in latitude. However, these two classes of particles are important because of the secondary neutrons they produce in the earth's atmosphere, which subsequently decay in the trapped particle region and contribute both protons and electrons to the Van Allen belts. Although the radiation belts have been examined in a large number of * Brookhaven N a t i o n a l L a b o r a t o r y , U p t o n , Long Island, N . Y . | Sandia C o r p o r a t i o n , Sandia Base, A l b u q u e r q u e , New Mexico. 899