Numerous Langmuir probes have flown in space, used to measure plasma properties, and their design has scarcely changed since they were first invented back in 1924: a series of voltages is applied to the probe, and the collected currents are used to identify properties of the plasma, such as electron and ion density, as well as temperature.

“A standard Langmuir probe performs a voltage sweep from negative to positive to gather plasma parameters,” explains Tore André Bekkeng of Norway’s Eidsvoll Electronics. “But it takes time to perform such a sweep, typically from a half to two seconds. Operating at orbital velocities of around 7 km per second means you are limited to at most one sample per 3.5 km of space – which is far too coarse to capture those small ionospheric structures that are disturbing, among other things, satellite navigation signals and cause what is known as ‘signal scintillations’.”

He adds that the multi-needle Langmuir Probe (m-NLP) instead extends a quartet of miniature cylinders, each set to a different, but fixed, voltage, producing a much narrower spatial resolution – down to less than two metres.