One of the major problems in trajectory and orbital estimation is to obtain a realistic estimate of the accuracy of the trajectory and other important parameters. In the orbital case, some of the parameters which may not be solved for are geopotential constants, survey, etc. These factors will affect the total uncertainty in the orbit and, of course, ephemeris predictions. A statistical technique is described that performs a variance-covariance propagation so as to obtain accuracy estimates based on random and unmodeled errors. An example of the unmodeled error propagation is shown for the Geos B satellite.