Floating Potential Probe

Spacecrafts may experience harmful effects due charging when exposed to a space environment.
Spacecraft charging can manifest as damage to onboard electronic instruments or interference with
scientific measurements. A floating potential probe can monitor the spacecraft potential and 1) provide a
real-time warning signal about high charging levels (~kV range), or 2) be used by a scientific instrument
to correct for platform charging effects at lower charging levels (a few V).

How is the problem solved today?

Today, spacecraft potentials are measured using variants of floating potential probes, like the e.g., the
Floating potential measurement unit (FPMU) mounted on the ISS (Barjatya et al., 2009), or using low-energy electron spectrometers. These are either large instrument and not well suited for e.g., smaller satellites, while spectrometers have the disadvantage of not supporting high voltages. Also, for
spectrometers, the time constant is longer since it needs to step through the complete energy range of
the spectrometer to get the curves required to calculate the potential. Meaning it is also a derived
parameter and not a direct physical measurement.

EIDEL Floating Potential Probe is an instrument initially developed by the University of Oslo and delivered in cooperation by EIDEL.

FPP Prototype (image: University of Oslo)

The m-NLP is also capable of measuring the floating potential. However, this is also a derived
measurement and limited to low voltage. A dedicated floating potential probe is aimed at measurement range up to the kV-range, and provide an independent measurement at the lower range. Both being physical measurements and not derived.