  We construct Saturn equatorial neutral temperature and density profiles of H,
H$_2$, He, and CH$_4$, between 10$^{-12}$ and 1 bar using measurements from
Cassini's Ion Neutral Mass Spectrometer (INMS) taken during the spacecraft's
final plunge into Saturn's atmosphere on 15 September 2017, combined with
previous deeper atmospheric measurements from the Cassini Composite InfraRed
Spectrometer (CIRS) and from the UltraViolet Imaging Spectrograph (UVIS). These
neutral profiles are fed into an energy deposition model employing soft X-ray
and Extreme UltraViolet (EUV) solar fluxes at a range of spectral resolutions
($\Delta\lambda=4\times10^{-3}$ nm to 1 nm) assembled from TIMED/SEE, from
SOHO/SUMER, and from the Whole Heliosphere Interval (WHI) quiet Sun campaign.
Our energy deposition model calculates ion production rate profiles through
photo-ionisation and electron-impact ionisation processes, as well as rates of
photo-dissociation of CH$_4$. The ion reaction rate profiles we determine are
important to obtain accurate ion density profiles, meanwhile methane
photo-dissociation is key to initiate complex organic chemical processes. We
assess the importance of spectral resolution in the energy deposition model by
using a high-resolution H$_2$ photo-absorption cross section, which has the
effect of producing additional ionisation peaks near 800 km altitude. We find
that these peaks are still formed when using low-resolution ($\Delta\lambda=1$
nm) or mid-resolution ($\Delta\lambda=0.1$ nm) solar spectra, as long as
high-resolution cross sections are included in the model.
