  PSR J0740+6620 is the neutron star with the highest precisely determined
mass, inferred from radio observations to be $2.08\pm0.07\,\rm M_\odot$.
Measurements of its radius therefore hold promise to constrain the properties
of the cold, catalyzed, high-density matter in neutron star cores. Previously,
Miller et al. (2021) and Riley et al. (2021) reported measurements of the
radius of PSR J0740+6620 based on Neutron Star Interior Composition Explorer
(NICER) observations accumulated through 17 April 2020, and an exploratory
analysis utilizing NICER background estimates and a data set accumulated
through 28 December 2021 was presented in Salmi et al. (2022). Here we report
an updated radius measurement, derived by fitting models of X-ray emission from
the neutron star surface to NICER data accumulated through 21 April 2022,
totaling $\sim1.1$ Ms additional exposure compared to the data set analyzed in
Miller et al. (2021) and Riley et al. (2021), and to data from X-ray
Multi-Mirror (XMM-Newton) observations. We find that the equatorial
circumferential radius of PSR J0740+6620 is $12.92_{-1.13}^{+2.09}$ km (68%
credibility), a fractional uncertainty $\sim83\%$ the width of that reported in
Miller et al. (2021), in line with statistical expectations given the
additional data. If we were to require the radius to be less than 16 km, as was
done in Salmi et al. (2024), then our 68% credible region would become
$R=12.76^{+1.49}_{-1.02}$ km, which is close to the headline result of Salmi et
al. (2024). Our updated measurements, along with other laboratory and
astrophysical constraints, imply a slightly softer equation of state than that
inferred from our previous measurements.
