Three solid-state detectors in an anticoincidence plastic scintillator observed electrons between 0.2 and 2.5 MeV; protons between 0.3 and 500 MeV; alpha particles between 2.0 and 200 MeV; heavy particles with Z values ranging from 2 to 5 with energies greater than 8 MeV; heavy particles with Z values ranging between 6 and 8 with energies greater than 32 MeV; and integral protons and alphas of energies greater than 50 MeV/nucleon, all with dynamic ranges of 1 to 1E+6 particles per (sq cm-s-sr). Five thin-window Geiger-Mueller tubes observed electrons of energy greater than 15 keV, protons of energy greater than 250 keV, and X rays with wavelengths between 2 and 10 A, all with a dynamic range of 10 to 1E+8 per (sq cm-s-sr). Particles and X rays, primarily of solar origin, were studied, but the dynamic range and resolution of the instrument also permitted observation of cosmic rays and magnetotail particles. For further details, see T. P. Armstrong et al., J. Geophys. Res., v. 83, p. 5198, 1978.