  The Extrasolar Planet Search with PRIMA project (ESPRI) aims at
characterising and detecting extrasolar planets by measuring the host star's
reflex motion using the narrow-angle astrometry capability of the PRIMA
facility at the Very Large Telescope Interferometer. A first functional
demonstration of the astrometric mode was achieved in early 2011. This marked
the start of the astrometric commissioning phase with the purpose of
characterising the instrument's performance, which ultimately has to be
sufficient for exoplanet detection. We show results obtained from the
observation of bright visual binary stars, which serve as test objects to
determine the instrument's astrometric precision, its accuracy, and the plate
scale. Finally, we report on the current status of the ESPRI project, in view
of starting its scientific programme.
