A rocket-borne Langmuir probe for in-situ measurement of ionospheric plasma

A Langmuir probe payload, to be flown on-board SONDA 3 and SONDA 4 rockets, is being developed at INPE. The major scientific objectives of the experiment are the measurements of electron density and electron temperature, the study of the spectral distribution of electron density irregularities in the ionosphere, and the study of the plasma irregularities in the equatorial electrojet. The payload basically consists of a Langmuir Probe sensor and an electronic system. A sweep voltage varying between -1V and +4V is applied to the sensor, and the current collected by it is converted into a varying voltage signal, and is amplified and telemetered to the ground. The sensor signal is processed through three different channels. The total signal at low gain is transmitted through one of the telemetry channels, the second channel carries the signal processed at an automatic gain control unit. The signal, after passing through a band pass filter, is transmitted through the third channel. The sensor current and its slope with respect to the sensor voltage, as measured through the first two channels, give information about the electron density and electron temperature, the third channel contains information about the electron density irregularities.