  The scope of this study is to model the solar-wind environment for the Parker
Solar Probe's unprecedented distances down to 9.86 Rs in its mission phase
during 2018-2025. The study is performed within the CGAUSS project which is the
German contribution to the PSP mission as part of the WISPR imager on PSP. We
present an empirical solar-wind model for the inner heliosphere which is
derived from OMNI and Helios data. The sunspot number (SSN) and its predictions
are used to derive dependencies of solar-wind parameters on solar activity and
to forecast them for the PSP mission. The frequency distributions for the
solar-wind key parameters magnetic field strength, proton velocity, density,
and temperature, are represented by lognormal functions, considering the
velocity distribution's bi-componental shape. Functional relations to the SSN
are compiled using OMNI data and based on data from both Helios probes, the
parameters' frequency distributions are fitted with respect to solar distance.
Thus, an empirical solar-wind model for the inner heliosphere is derived,
accounting for solar activity and solar distance. The inclusion of SSN
predictions and the extrapolation down to PSP's perihelion region enables us to
estimate the solar-wind environment for PSP's planned trajectory during its
mission duration. This empirical model yields estimated solar-wind values for
PSP's 1st perihelion in 2018 at 0.16 au: 87 nT, 340 km s-1, 214 cm-3 and 503000
K. The estimates for PSP's first closest perihelion, occurring in 2024 at 0.046
au, are 943 nT, 290 km s-1, 2951 cm-3, and 1930000 K. Since the modeled
velocity and temperature values below approximately 20 Rs appear overestimated
in comparison with existing observations, this suggests that PSP will directly
measure solar-wind acceleration and heating processes below 20 Rs as planned.
