  In an earlier study, we reported that the ram gauge of the COmet Pressure
Sensor (COPS), one of the three instruments of the Rosetta Orbiter Spectrometer
for Ion and Neutral Analysis (ROSINA), could be used to obtain information
about the sublimating content of icy particles, made up of volatiles and
conceivably refractories coming from comet 67P/Churyumov-Gerasimenko.
  In this work, we extend the investigation to the second COPS gauge, the nude
gauge. In particular, we analyse the volume of the volatile content of coma
particles, along with a search for possible dependencies between the nude gauge
detection rate (i.e. the rate at which icy particles are detected by the nude
gauge) and the position of the Rosetta spacecraft. We also investigate the
correlations of the nude gauge detection rate with the quantities associated
with cometary activity.
  Although it was not originally designed for such a purpose, the COPS nude
gauge has been able to detect $\sim$67000 features generated by the sublimation
of the volatile content of icy particles. The nude gauge detection rate follows
a trend that is inversely proportional to the heliocentric distance. This
result is interpreted as a confirmation of a possible relation between the nude
gauge detection rate and cometary activity. Thus, we compared the former with
parameters related to cometary activity and obtained significant correlations,
indicating that the frequency of icy particle detection is driven by cometary
activity. Furthermore, by representing the volatile part of the icy particles
as equivalent spheres with a density of 1 g cm$^{-3}$, we obtained a range of
diameters between 60 and 793 nanometres, with the smaller ones
($<390\,\mathrm{nm}$ in diameter) having a size distribution power index of
$-4.79\pm 0.26$.
