s. Increases in inclination of the spacecraft orbit result in more significant increases in solar proton exposure than does increase in orbit altitude. Because solar particle events may coincide with geomagnetic field disturbances the ability of solar heavy ions propagate to lower altitudes and lower latitude regions must also be considered. Plasma Environment and Spacecraft Charging [Frederickson96] [Tribble95][Holbert96] Near-Earth satellites encounter energetic charged particles; a population of both positively charged ions and negatively charged electrons - plasma. The external surfaces of spacecraft experience a higher flux of electrons than ions, charging the body of the spacecraft negatively with respect to the nearby ambient plasma, resulting in surface charging. Although surface charging may potentially result in effects on the spacecraft, the limited energy storage associated with the small capacitance of the spacecraft to the ambient plasma indicates that this is not a major contributor to anomalies. One area of concern in regard to surface charging is the potential for reattraction of contaminant ions. A percentage of the neutral atoms outgassed by spacecraft materials may become ionized by solar UV and be attracted to sensitive charged surfaces. In differential surface charging, differences in the emission and absorption characteristics of materials, differences in sunlight exposure, and localized effects resulting in unequal electron populations produce voltage differences between insulated satellite surfaces. Electrons having sufficient energy to pass through the thermal blanket result in internal charging of surfaces and assemblies. Typical insulated objects include cable jackets, ungrounded thermal wrap, thermal paint, component encapsulants, etc. Higher energy electrons penetrating subsystem chassis assemblies may deposit charge onto circuit board and wire insulators, connectors, capacitors, etc. In this process, termed deep dielectric charging, high- energy electrons penetrate circuit elements 