[ Thanks to Edwood
Ocasio for this link. ]
“his project (timeephem.sf.net) consists of software and
associated data to help create, manipulate, and interpolate time
ephemerides of the Earth. Such ephemerides are used to correct
pulse arrival times from pulsars (and any other Earth-based
astronomical or spacecraft observation where precise timing is
critical) for the general relativistic distortion of the rate of
Earth-based clocks. Such distortion is a well-known effect due to
the time-varying velocity of Earth-based clocks relative to the
solar system barycenter and also due to the time-varying
gravitational potential at the position of such clocks due to the
detailed motions of all major masses in the solar system relative
to the clock location. Thus, an important prerequisite of any
calculation of a time ephemeris is a JPL planetary ephemeris, which
represents some of man’s best knowledge of the masses, positions
and velocities of all major solar system objects.”