The Voyager 1 Jupiter reconstructed spacecraft trajectory file:

  vg1.jup204.nio

was produced by R. Jacobson of the  JPL Solar System Dynamics Group
as part of his work in improving the ephemerides of Jupiter's
natural satellites. It was made using all available radio tracking
and optical navigation data. As such, it should be the best currently
available trajectory solution for the Voyager 1 spacecraft during 
the Jupiter flyby. However, Jacobson has indicated (private
communication) that further improvements are possible and expected;
just not sure when.

NAIF has no "accuracy" information about the SPICE SPK file made
from the source file identified above other than the implication
of "current best" already expressed.

Charles Acton/NAIF
2007 Jan 26