The difference in the Mars prime meridian location between the Mars orientation model MRO120G and the corresponding models from MRO120F (A. S. Konopliv et al. 2020) and the IAU 2011 on the surface of Mars. The “time-series” differences use Table A1 for Δϕ_cor, whereas the “periodic fit” uses the periodic approximation for the time series as given by Equation (26). The recommended MRO120G model as given in Table 4 uses the periodic fit (“light purple” and “red” curves).