Impedance probe technique to detect the absolute number density of electrons on-board spacecraft

Abstract

This text focuses on the impedance probe which is powerful method for observation of absolute electron density in plasma. In several countries, impedance probe has been used during many rocket campaigns and satellite missions by many scientists' groups. In Japan, Oya (1966) realized remarkably accurate electron density observation on-board sounding rocket. Since then, the impedance probe has taken part in absolute electron density measurement to proceed ionospheric and space plasma science in Japan. This text aims to describe impedance probe method which is developed by Oya (1966) as excellent example of in-situ observation of absolute electron density. The following description will provide the historical background, basic theory, advantages, important reminders and specific application ideas of sounding rocket observations during SEEK-2, DELTA and WIND campaigns. This text will refrain from commenting a lot about impedance probe instruments on-board satellites because the authors don't have many experiences with carrying out satellite missions. However, description in this issue will provide some information for future application of satellite experiment. It is expected that engineers, scientists and graduate students who attempt to carry out such impedance probe observation will find effective skills of the method through the text.