Comparison of cylindrical electrostatic probe measurements on Alouette II and explorer XXXI satellites

The Alouette II and Explorer XXXI satellites were placed in orbit by a single launch vehicle and separated. Cylindrical electrostatic probes of identical design were installed on each satellite in part to test the effects of the long sounder antennas and large radio-frequency power on Alouette II upon direct measurements of the thermal electrons and ions. Comparisons of the early data, taken when the satellites were separated less than 1000 km along their common orbit, suggest that there is no inherent incompatibility between the sounder experiment and direct measurement experiments. The electron temperature T
e
and concentration N
e
derived from the two experiments generally agree to better than 10 percent, although unexplained differences of up to 15 percent in T
e
and 40 percent in N
e
have been found on rare occasions.