Measurements of 0.2 to 20 GeV/n cosmic-ray proton and helium spectra   from 1997 through 2002 with the BESS spectrometer
  We measured low energy cosmic-ray proton and helium spectra in the kinetic energy range 0.215 - 21.5 GeV/n at different solar activities during a period from 1997 to 2002. The observations were carried out with the BESS spectrometer launched on a balloon at Lynn Lake, Canada. A calculation for the correction of secondary particle backgrounds from the overlying atmosphere was improved by using the measured spectra at small atmospheric depths ranging from 5 through 37 g/cm^2. The uncertainties including statistical and systematic errors of the obtained spectra at the top of atmosphere are 5-7 % for protons and 6-9 % for helium nuclei in the energy range 0.5 - 5 GeV/n. 
Y. Shikaze, S. Haino, K. Abe, H. Fuke, T. Hams, K. C. Kim, Y. Makida,   S. Matsuda, J. W. Mitchell, A. A. Moiseev, J. Nishim...