The Electron-Proton-Angle Spectrometer (EPAS) was one of the two parts of the Medium Energy Electron Spectrometer and measured electrons in the energy range of 16-300 keV and protons in the range of 20-3300 keV. EPAS, also called MEB or Sensor B, was composed of two identical units each consisting of a collimator, a focusing magnet assembly, a support structure, five solid-state detectors in the focal curve of the magnet assembly for electron detection, and two 2-element solid-state telescopes viewing the collimator through the magnetic field for ion (mainly proton) detection. The magnetic field was homogeneous over most of the volume defined by the pole pieces with a strength of about 0.08 T. The magnetic field geometry was such that electrons of all energies between 16 and 300 keV were deflected through about 180 deg and focused at a point corresponding to the entrance angle of the electron. The five detectors provided five angular intervals within the 60-deg field of view of each unit. The electron energy spectrum was determined by pulse-height analysis of a selected solid-state detector and the energy range was divided into 15 approximately logarithmically spaced channels, which provided a delta E/E of about 0.35. An integral energy channel above 22 keV was also provided. The look directions of the 10 electron detectors with respect to the spacecraft spin axis were 10, 20, 30, 40, 50, 80, 90, 100, 110, and 120 deg. Angular resolutions, in degrees, were: elevation - 3; azimuth - 2. The geometric factor for each detector element was 5.E-5 sq cm-sr. The proton/ion telescopes employed pulse-height analysis of a selected front counter and the 20 to 3300-keV energy interval was divided into 12 approximately logarithmically spaced channels, which provided a delta E/E of about 0.3, except for the highest channel, which covered the range 403 - 3300 keV. An integral energy channel above 27 keV was also provided. The ion angles with respect to the spacecraft spin axis were centered at 23, 46, 83, and 106 deg. Angular resolutions in degrees were: elevation - 5; azimuth - 2. The geometric factor for each telescope is 2.E-4 sq cm-sr. This experiment was part of the SPACERAD project sponsored by AFGL.