  The Neutron star Interior Composition ExploreR (NICER) is expected to launch
in early 2017 and will gather X-ray data on neutron stars and other high-energy
sources from a berth on the International Space Station. Its prime scientific
goal is to measure the masses and radii of non-accreting neutron stars via fits
to the energy-dependent waveforms produced by the rotation of hot spots on
their surfaces. These measurements will provide valuable input to theoretical
models of cold matter beyond nuclear density. Here we propose that PSR
J1614$-$2230, despite its low count rate, is a promising source to observe with
NICER. The reason is that XMM-Newton observations suggest that the fractional
oscillation amplitude from PSR J1614$-$2230 could be high enough that this star
cannot be very compact. We show that if we analyze 0.5 Ms of NICER data and 0.1
Ms of nearby off-source data and combine that analysis with the known mass of
this star, we would find a robust lower limit to the radius with a statistical
uncertainty of only $\sim 0.5-0.7$ km. We also show that even if there is an
unmodeled nonthermal component modulated at the pulsation frequency, good
statistical fits could rule out significant biases. The low count rate will
make reliable upper limits on the radius difficult, but the lower limit could
rule out some equations of state that are currently being discussed. This
analysis would require a good estimate of the non-source background, so Chandra
observations of the vicinity of PSR J1614$-$2230 would be helpful.
