Experiences modeling, simulating, and evaluating satellite and ground support systems using the OPNET tool are presented. The specific instance presented concerns work performed as part of a Nuclear Detonation Detection System (NDS) trade study. Models to be presented include a UHF satellite, mobile and fixed ground systems, and airborne systems. Model presentations start and proceed through scenario, node, component(s), detailed component attributes, and code variations providing a look at engineering level modeling of complex SATCOM systems. Traffic used in the scenarios is continuous transmission of message traffic used to evaluate the ability of UHF systems to perform in a "worst case" high altitude nuclear burst environment. Nuclear effects on RF signal propagation are identified and defined. Models and their simulation results provide a look at the capability of the OPNET tool in evaluating the capability of current as well as proposed future space and terrestrial communications systems from both the operational and acquisition perspectives when the systems are subjected to nuclear disturbed environments.