Langmuir probe

Langmuir probes have been installed on satellites and sounding rockets to observe the general characteristics of thermal plasma in the ionosphere for more than five decades. Because of its simplicity and convenience, the Langmuir probe is one of the most frequently installed scientific instruments on spacecraft. While the algorithm to estimate the temperature and number density of thermal electrons from Langmuir probe measurements is relatively simple, a number of factors, such as the position of probe installation, probe surface contamination, and electronic circuit design, have to be considered for accurate measurements. In fact, the accuracy is primarily influenced by improving implementation errors rather than the validity of the Langmuir probe approximation for the observed current versus voltage characteristics for the temperature and density estimates. In this paper, we present an example of an actual specification for a Langmuir probe and its electronics along with data gathered on a sounding rocket and a satellite in the ionosphere. Several new applications of Langmuir probes are introduced.