  The BESS-Polar Collaboration measured the energy spectra of cosmic-ray
protons and helium during two long-duration balloon flights over Antarctica in
December 2004 and December 2007, at substantially different levels of solar
modulation. Proton and helium spectra probe the origin and propagation history
of cosmic rays in the galaxy, and are essential to calculations of the expected
spectra of cosmic-ray antiprotons, positrons, and electrons from interactions
of primary cosmic-ray nuclei with the interstellar gas, and to calculations of
atmospheric muons and neutrinos. We report absolute spectra at the top of the
atmosphere for cosmic-ray protons in the kinetic energy range 0.2-160 GeV and
helium nuclei 0.15-80 GeV/nucleon. The corresponding magnetic rigidity ranges
are 0.6-160 GV for protons and 1.1-160 GV for helium. These spectra are
compared to measurements from previous BESS flights and from ATIC-2, PAMELA,
and AMS-02. We also report the ratio of the proton and helium fluxes from 1.1
GV to 160 GV and compare to ratios from PAMELA and AMS-02.
