NRL SP ADE-2 Plasma Diagnostic Electronics

The Space Plasma Diagnostic Suite (SPADE) is composed of a Langmuir probe and a plasma impedance probe for high-frequency measurements and measures plasma density and plasma electron temperature in the Earth's ionosphere. A transimpedance amplifier comprises the heart of the Langmuir probe and measures the low-frequency probe current in response to a sawtooth voltage stimulus. The plasma impedance probe uses direct digital synthesis and a pair of gilbert cell mixers to measure the high-frequency probe current and voltage, from which the antenna impedance is derived. Two conductive elements comprise the active surface of the sensor, driven at the same potential for Langmuir probe measurements and used as a short dipole antenna for impedance probe measurements.