A primary indicator of the accuracy of orbit determination based on Doppler tracking is the graph of residuals vs time. Parameter errors in the orbit determination model produce characteristic signatures in the residuals plot. A systematic method of modeling the signature due to a parameter error by means of first and second partial derivative approximations is presented. Signatures due to errors in station location, solar pressure, relativistic clock, and the Earth's troposphere are compared with residual plots from a spacecraft mission, corresponding to the introduction of the same parametric error into orbit determination software. A comparison of postfit residuals with and without the introduction of known modeling errors demonstrates that some errors can be masked by apparent convergence, resulting in erroneous estimates.