  Momentum spectra of charged pions over nearly full rapidity coverage from
target to beam rapidity have been measured in the 0-5% most central Au+Au
collisions in the beam energy range from 2 to 8 AGeV by the E895 Experiment.
Using a thermal parameterization to fit the transverse mass spectra, rapidity
density distributions are extracted. The observed spectra are compared with
predictions from the RQMD v2.3 cascade model and also to a thermal model
including longitudinal flow. The total 4$\pi$ yields of the charged pions are
used to infer an initial state entropy produced in the collisions.
