The Langmuir plate and spherical ion probe experiments aboard explorer XXXI

Two probe experiments aboard Explorer XXXI measure the concentrations and temperatures of the thermal electrons and major ion species encountered by the satellite. A brief description of the instruments is given and examples of data are presented to illustrate special features which could be relevant when contrasting results with those from other experiments on Explorer XXXI or Alouette II. Comparison with data from the ionosonde aboard the latter provided information on the effective collecting area of the probes and the influence of the plasma sheath surrounding the satellite.