  Pulsar timing arrays (PTAs) can be used to study the Solar-system ephemeris
(SSE), the errors of which can lead to correlated timing residuals and
significantly contribute to the PTA noise budget. Most Solar-system studies
with PTAs assume the dominance of the term from the shift of the Solar-system
barycentre (SSB). However, it is unclear to which extent this approximation can
be valid, since the perturbations on the planetary orbits may become important
as data precision keeps increasing. To better understand the effects of SSE
uncertainties on pulsar timing, we develop the LINIMOSS dynamical model of the
Solar system, based on the SSE of Guangyu Li. Using the same input parameters
as DE435, the calculated planetary positions by LINIMOSS are compatible with
DE435 at centimetre level over a 20-year timespan, which is sufficiently
precise for pulsar-timing applications. We utilize LINIMOSS to investigate the
effects of SSE errors on pulsar timing in a fully dynamical way, by perturbing
one SSE parameter per trial and examining the induced timing residuals. For the
outer planets, the timing residuals are dominated by the SSB shift, as assumed
in previous work. For the inner planets, the variations in the orbit of the
Earth are more prominent, making previously adopted assumptions insufficient.
The power spectra of the timing residuals have complex structures, which may
introduce false signals in the search of gravitational waves. We also study how
to infer the SSE parameters using PTAs, and calculate the accuracy of parameter
estimation.
