Cumulative probability of the circumferential radius for a hydrogen atmosphere model of synthetic energy-resolved NICER data for PSR J1614−2230. The lines are labeled with the radius that was assumed in the generation of the synthetic data. See text for details of the runs. Statistical fluctuations in the data lead to the unequal spacing of the lines. The R = 15.4 km, ﹩{\theta }_{c}=40^\circ ﹩ run was performed to test the hypothesis that it is the frms that provides the major constraints, and indeed we see that the cumulative probability distribution is almost the same as for the R = 11 km, ﹩\theta =90^\circ ﹩ case, which has the same frms but different harmonic content. This figure shows that the high quality of NICER data could yield useful constraints on the radius. We also note that at smaller radii the lines rise more steeply, because at smaller radii the maximum amount of light deflection increases more rapidly with decreasing radius than at larger radii, and hence the waveform is smoothed out more efficiently at smaller radii.