  The Ion Composition Analyzer (ICA) on the Rosetta spacecraft observed both
the solar wind and the cometary ionosphere around comet
67P/Churyumov-Gerasimenko for nearly two years. However, observations of low
energy cometary ions were affected by a highly negative spacecraft potential,
and the ICA ion density estimates were often much lower than plasma densities
found by other instruments. Since the low energy cometary ions are often the
highest density population in the plasma environment, it is nonetheless
desirable to understand their properties. To do so, we select ICA data with
densities comparable to those of Rosetta's Langmuir Probe (LAP)/Mutual
Impedance Probe throughout the mission. We then correct the cometary ion energy
distribution of each energy-angle scan for spacecraft potential and fit a
drifting Maxwell-Boltzmann distribution, which gives an estimate of the drift
energy and temperature for 3521 scans. The resulting drift energy is generally
between 11--18 eV and the temperature between 0.5--1 eV. The drift energy shows
good agreement with published ion flow speeds from LAP during the same time
period and is much higher than the cometary neutral speed. We see additional
higher energy cometary ions in the spectra closest to perihelion, which can
either be a second Maxwellian or a kappa distribution. The energy and
temperature are negatively correlated with heliocentric distance, but the slope
of the change is small. It cannot be quantitatively determined whether this
trend is primarily due to heliocentric distance or spacecraft distance to the
comet, which increased with decreasing heliocentric distance.
