  Many physical parameters that can be estimated from space mission tracking
data influence both the translational dynamics and proper time rates of
observers. These different proper time rates cause a variability of the time
transfer observable beyond that caused by their translational (and rotational)
dynamics. With the near-future implementation of (interplanetary) transponder
laser ranging, these effects will become increasingly important, requiring a
re-evaluation of the common data analysis practice of using a priori time
ephemerides, which is the goal of this paper.
  We develop a framework for the simultaneous estimation of the initial
translational state and the initial proper time of an observer, with the goal
of facilitating robust tracking data analysis from next-generation space
missions carrying highly accurate clocks and tracking equipment. Using our
approach, the influence of physical parameters on both translational and time
dynamics are considered at the same level in the analysis, and mutual
correlations between the signatures of the two are automatically identified. We
perform a covariance analysis using our proposed method with simulated laser
data from Earth-based stations to both a Mars and Mercury lander.
  Using four years of tracking data for the Mars lander simulations, we find a
difference between our results using the simultaneous space-time dynamics
estimation and the classical analysis technique (with an ta priori time
ephemeris) of around 0.1 % in formal errors and correlation coefficients. For a
Mercury lander this rises to around 1% for a 1-month mission and 10 % for a
4-year mission. By means of Monte Carlo simulation, we find that using an a
priori time ephemeris of representative accuracy will result in estimation
errors that are orders of magnitude above the formal error when processing
highly accurate laser time transfer data.
