A semi-theoretical model of the upper atmosphere was constructed to allow the calculation of the primary atmospheric properties from 90 to 10,000 km altitude as a function of local time and solar activity. The calculations are based upon an empirical density profile from a density model as the initial input. Assuming diffusive equilibrium above 110 km and isothermal conditions above 400 km, the remaining properties (pressure, temperature, mean molecular mass, and the individual particle concentrations) are derived by using the hydrostatic equation and equation of state, together with boundary values from measurements. To illustrate the model, two tables are given that present the average atmospheric properties vs altitude for sunspot maximum and minimum conditions, respectively, for the months immediately following the Argus (September 1958) and Starfish (July and August 1962) high-altitude nuclear detonations.