CLP (Constant-biased Langmuir Probe)


A main objective of this instrument is to monitor a relative variation of the electron current, which is generally thought to be proportional to the ambient plasma density, during the rocket flight. The measured variation will be compared with the neutral temperature from NTV observation and the neutral wind from the ground-based Fabry-Perot Interferometer observation for a study of the dynamics and energetics in the lower thermosphere.

Instrument specification

A gold-coated spherical probe with a diameter of 3 cm is put on the top of payload zone of the rocket. The probe is biased with a voltage of +5 V with respect to the rocket potential in order to measure the saturated electron current even when the rocket is negatively charged to a minus few V. The electron current incident to the probe is amplified and subsequently transferred to the telemeter. Two levels of the current gain; 1 time and 100 times, are prepared so that the probe can measure in a wide range of the electron density.

Detailed Specification of the CLP instrument is as follows:

Applied voltage+5V with respect to the rocket potential
Sampling period2.5 msec
Weight0.15kg (CLP-S)
0.20kg (CLP-PRE)
Size100 x 30 x 140H mm (CLP-S)
80 x 30 x 70H mm (CLP-PRE)
Power20mA (+18V), 20mA (-18V)
Telemeter outputCLP-H NA22


T. Abe (ISAS/JAXA), K.-I. Oyama (ISAS/JAXA), AD Co., Ltd.