  Past years have seen various publications attempting to explain the apparent
clustering features of trans-Neptunian objects, the most popular explanation
being an unconfirmed "Planet 9". The recently proposed Uranus Orbiter and Probe
mission by NASA's Planetary Science and Astrobiology Decadal Survey could offer
the opportunity to precisely determine Planet 9's sky location and mass by
carefully monitoring ranging data during the interplanetary cruise. We use
Monte Carlo-Markov Chain methods to reconstruct simulated spacecraft
trajectories in a simplified solar system model containing Planet 9, providing
an estimate of the mission's localisation capacity depending on sky location,
Earth-spacecraft Doppler link noise level and data collection rate. We
characterise the noise via the Allan deviation $\sigma_{\rm A}$, scaled to the
Cassini-era value $\sigma_{\rm A}^{\rm \scriptscriptstyle Cass} = 3 \times
10^{-15}$, finding that daily measurements of the spacecraft position can lead
to $\sim$0.2 deg$^2$ localisation of Planet 9 (assuming $M_9 = 6.3 M_{\oplus}$,
$d_9 = 460$AU). As little as a 3-fold improvement in $\sigma_{\rm A}$
drastically decreases the sky localisation area size to $\sim$0.01 deg$^2$.
Thus, we showcase that a future Uranus mission carries a significant potential
also for non-Uranian science.
