This paper reviews those aspects of the near-earth space environment that could have potentially adverse effects on electro-optical systems and their operations in space. As such systems have grown in complexity, their susceptibility to damage by the space environment has grown comparably. As the mission lifetimes have increased, the long term effects of radiation damage, spacecraft charging, and surface contamination have become significant concerns. Current models of the charged particle environment responsible for these effects are presented from the standpoint of their applicability to design needs. Although much still needs to be done, these models are sufficiently accurate that significant improvements can be made in system survivability if the models are employed early in the design phase.