  High-precision ephemerides are not only useful in supporting space missions,
but also in investigating the physical nature of celestial bodies. This paper
reports an update to the orbit and rotation model of the Martian moon Phobos.
In contrast to earlier numerical models, this paper details a dynamical model
that fully considers the rotation of Phobos. Here, Phobos' rotation is first
described by Euler's rotational equations and integrated simultaneously with
the orbital motion equations. We discuss this dynamical model, along with the
differences with respect to the model now in use.
  We present the variational equation for Phobos' rotation employing the
symbolic \emph{Maple} computation software. The adjustment test simulations
confirm the latitude libration of Phobos, suggesting gravity field coefficients
obtained using a shape model and homogeneous density hypothesis should be
re-examined in the future in the context of dynamics. Furthermore, the
simulations with different $k_2$ values indicate that it is difficult to
determine k_2 efficiently using the current data.
