  Two years of neutral measurements by IBEX-Lo have yielded several direct
observations of interstellar neutral helium and oxygen during preferred viewing
seasons. Besides the interstellar signal, there are indications of the presence
of secondary neutral helium and oxygen created in the heliosphere. Detailed
modeling of these particle species is necessary to connect the measured fluxes
to the pristine local interstellar medium while accounting for loss and
production of neutral particles during their path through the heliosphere. In
this contribution, global heliosphere models are coupled to analytic
calculations of neutral trajectories to obtain detailed estimates of the
neutral distribution function of primary interstellar helium atoms in the
heliosphere, in particular in the inner heliosphere.
