  K2 Campaign 9 (K2C9) offers the first chance to measure parallaxes and masses
of members of the large population of free-floating planets (FFPs) that has
previously been inferred from measurements of the rate of short-timescale
microlensing events. Using detailed simulations of the nominal campaign
(ignoring the loss of events due to Kepler's emergency mode) and ground-based
microlensing surveys, we predict the number of events that can be detected if
there is a population of 1-Jupiter-mass FFPs matching current observational
constraints. Using a Fisher matrix analysis we also estimate the number of
detections for which it will be possible to measure the microlensing parallax,
angular Einstein radius and FFP mass. We predict that between 1.4 and 7.9
events will be detected in the K2 data, depending on the noise floor that can
be reached, but with the optimistic scenario being more likely. For nearly all
of these it will be possible to either measure the parallax or constrain it to
be probabilistically consistent with only planetary-mass lenses. We expect that
for between 0.42 and 0.98 events it will be possible to gain a complete
solution and measure the FFP mass. For the emergency mode truncated campaign,
these numbers are reduced by 20~percent. We argue that when combined with
prompt high-resolution imaging of a larger sample of short-timescale events,
K2C9 will conclusively determine if the putative FFP population is indeed both
planetary and free-floating.

Earth and Planetary Astrophysics