  We present synthetic radio images of the GRB170817A afterglow, computed from
moving-mesh hydrodynamic simulations of binary neutron star merger outflows.
Having expanded for nearly a year, the merger remnant is expected to subtend
roughly 5 milli-arcseconds (mas) on the sky, potentially resolvable by very
long baseline radio imaging techniques. Any observations revealing the radio
centroid to be offset from the line-of-site to the merger would be the smoking
gun of a jetted outflow. However, our results indicate that a measurement of
the centroid position alone cannot independently determine whether that jet
escaped successfully from the merger debris cloud, or was "choked," yielding a
quasi-spherical explosion. We find that in both scenarios, the centroid
exhibits superluminal proper motion away from the merger site at roughly 4 - 10
mas per day for at least the first 300 days. We argue that a successful
strategy for differentiating among the explosion models will need to include
multiple observations over the coming months - years. In particular, we find
the time at which the centroid attains its maximum offset, and begins heading
back toward the merger site, is considerably later if the jet was choked.
Detecting a reversal of the centroid trajectory earlier than 600 days would
uniquely identify a successful jet. Our results indicate the source might be
resolved using VLBI radio observing techniques with roughly 1 mas resolution
starting at roughly 400 days post-merger, and that the the angular extent of a
successful jet is significantly smaller than that of a choked jet (4.5 versus 7
mas respectively).
