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Charges as small as 1 pC degrade the performance of high precision inertialreference instruments when accumulated on their test masses (TMs). Non-contactcharge management systems are required for the most sensitive of theseinstruments, with the TMs free-floating, and their charges compensated byphotoelectrons in a feedback loop with a TM charge measurement. Three spacemissions have successfully demonstrated this technique: GP-B, LPF, and theUV-LED mission. Charge management techniques that eliminate the chargemeasurement and feedback systems, referred henceforth as passive, reduce thecomplexities and disturbance effects introduced by these systems, and are thusthe subject of active research and development work. Passive charge managementdepends critically on the stability and reproducibility of the photoemissionproperties of a given system. In support of this work, we present comprehensiveflight characterization data for a suite of 16 UV-LEDs in variousconfigurations and 255+/-1 nm center wavelength. Flight data was acquiredbetween December 2014 and December 2015 with the UV-LED instrument flown onSaudiSat 4. We back up our results with ground-based measurements performed inconfigurations comparable to the flight one between September 4, 2020, andOctober 8, 2020. All results confirm the excellent reliability of the UV-LEDsin the space environment, are fully consistent with the findings of groundstudies, and support the approach of using LEDs for passive charge management.We find that the equilibrium potential of the TM, under illumination by the 255nm LEDs, is independent of the UV intensity and reproduceable to about +/- 6mV, or +/-6 fC/pF, over periods of up to six months. The value of theequilibrium potential is dependent on the geometry of the electric fieldbetween the TM and its enclosure, and thus on the exact configuration of theinstrument.

Flight and ground demonstration of reproducibility and stability of photoelectric properties for passive charge management using LEDs