  We present COPAINS (Code for Orbital Parametrisation of Astrometrically
Inferred New Systems), an innovative tool developed to identify previously
undiscovered companions detectable via direct imaging, based on changes in
stellar proper motions across multiple astrometric catalogues. This powerful
procedure allows for dynamical predictions of the possible masses and
separations of unseen companions compatible with observed astrometric trends,
marginalised over unknown orbital elements. Validating our approach using
well-constrained systems, we found that our tool provides a good indication of
the region of the parameter space where undetected secondaries may be located.
Comparing the output of the code to the measured or expected sensitivity from
various imaging instruments, this in turn enables us to robustly select the
most promising targets for direct imaging campaigns searching for low-mass
companions. Such an informed selection method promises to reduce the null
detection rates from current programs and will significantly increase the
current census of wide brown dwarfs and planetary companions to stars, which
remain extremely rare in the surveys conducted so far.
