Abstract : The Harry Diamond Laboratories of the U.S. Army electronics Research and Development Command was tasked to help develop standard environmental conditions pertaining to limited visibility operations, for training, research, development, and analysis. This task was part of an effort to ensure use of realistic battlefield environmental conditions throughout the Army. To support this effort, this report provides background information, definitions, criteria for setting standards, and data for selected environmental conditions. The definitions of standards are based on an extension to system operability of the definitions given for physical survivability in Army Regulation AR 70-38, Research, Development, Test, and Evaluation of Materiel for Extreme Climatic Conditions. The objective is to have a procedure for determining the probability of successful performance of signal links of weapon systems that can be affected by environment. Data presented here include those environmental parameters that affect the performance of electro-optical links of military systems. These parameters include transmission and reflectance data. Transmission data are provided for visibility, ceiling, rain and snow rates, and humidity. These data are provided in terms of risk that a given level will be exceeded, based on the definitions of AR 70-38.