The purpose of this experiment was to study the global variations of electron temperature and electron concentration at S/C altitudes during solar maximum, and to study characteristics of the S/C ion sheath. The measurements were made with two cylindrical probes, operating as Langmuir probes. There were a boom probe and an axial probe. The axial probe extended 48.3 cm from the S/C, along the spin axis, and was centered among the four telemetry antennas on the underside of the S/C. This probe was capable of measurements undisturbed by the satellite motion only when the probe preceded the S/C in its motion through the plasma. The boom probe extended horizontally and outward (in S/C frame of reference) from a boom 1 m long, which in turn extended from an upper surface of the S/C at an angle of about 45 deg to the spin axis. This probe provided some observations during each S/C spin cycle that were free of S/C wake effects. The probes consisted of three concentric, electrically isolated, stainless steel tubes. The outer (0.24-cm diam and 23-cm long) tube floated at its own equilibrium potential and served to place the collector well away from the S/C plasma sheath. The middle tube (0.165-cm diam) extending 23 cm outward from the outer tube acted as an electrical guard for the collector. Its electrical potential was controlled. The collector (0.058-cm diam) extended 23 cm outward from the driven guard. During each 2-min sequence, a volt-ampere curve was obtained from the sawtooth voltage (-2 to +10 V) applied to the collector. This was interpreted in electron densities over a range from 1.E2 to 1.5E6 electrons per cc, and temperatures from about 400 to 5.E4 deg K. NSSDC has all the useful data that exist from this investigation.