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Precise control over the potential of an electrically isolated proof mass isnecessary for the operation of devices such as a Gravitational Reference Sensor(GRS) and satellite missions such as LISA. We show that AlGaN UV LEDs operatingat 255 nm are an effective substitute for Mercury vapor lamps used in previousmissions because of their ability to withstand space qualification levels ofvibration and thermal cycling. After 27 thermal and thermal vacuum cycles and 9minutes of 14.07 g RMS vibration, there is less than 3% change in current draw,less than 15% change in optical power, and no change in spectral peak or FWHM(full width at half maximum). We also demonstrate UV LED stimulatedphotoemission from a wide variety of thin film carbide proof mass coatingcandidates (SiC, Mo2C, TaC, TiC, ZrC) that were applied using electron beamevaporation on an Aluminum 6061-T6 substrate. All tested carbide films havemeasured quantum efficiencies of 3.8-6.8*10^-7 and reflectivities of 0.11-0.15,which compare favorably with the properties of previously used gold films. Wedemonstrate the ability to control proof mass potential on an 89 mm diameterspherical proof mass over a 20 mm gap in a GRS-like configuration. Proof masspotential was measured via a non-contact DC probe, which would allow controlwithout introducing dynamic forcing of the spacecraft. Finally we provide alook ahead to an upcoming technology demonstration mission of UV LEDs andfuture applications toward charge control of electrically isolated proofmasses.

UV LED charge control of an electrically isolated proof mass in a Gravitational Reference Sensor configuration at 255 nm