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In this paper, we present the design and performance of the upgraded University of Florida torsion pendulum facility for testing inertial sensor technology related to space-based gravitational wave observatories and geodesy missions. In particular, much work has been conducted on inertial sensor technology related to the Laser Interferometer Space Antenna (LISA) space gravitational wave observatory mission. A significant upgrade to the facility was the incorporation of a newly designed and fabricated LISA-like gravitational reference sensor (GRS) based on the LISA Pathfinder GRS. Its LISA-like geometry has allowed us to make noise measurements that are more representative of those in LISA and has allowed for the characterization of the mechanisms of noise induced on a LISA GRS and their underlying physics. Noise performance results and experiments exploring the effect of temperature gradients across the sensor will also be discussed. The LISA-like sensor also includes unique UV light injection geometries for UV LED based charge management. Pulsed and DC charge management experiments have been conducted using the University of Florida charge management group’s technology readiness level 4 charge management device. These experiments have allowed for the testing of charge management system hardware and techniques as well as characterizations of the dynamics of GRS test mass charging. The work presented here demonstrates the upgraded torsion pendulum’s ability to act as an effective testbed for GRS technology.

There is increasing interest in deep UV Light-Emitting Diodes (LEDs) for applications in water purification, virus inactivation, sterilization, bioagent detection, and UV curing, as well as charge management control in the Laser Interferometer Space Antenna (LISA), which will be the first gravitational wave detector in space. To fully understand the current state of commercial UV LEDs and assess their performance for use on LISA, large numbers of UV LEDs need to be tested across a range of temperatures while operating in air or in a vacuum. We describe a new hardware system designed to accommodate a high volume of UV LED performance tests and present the performance testing results from over 200 UV LEDs with wavelengths in the 250 nm range.

Space-based gravitational wave detection will be carried out by the laser interferometer space antenna (LISA), a joint European Space Agency and NASA collaboration. The configuration of this antenna will include three identical spacecraft in a triangular formation separated by [Formula: see text], flying in a drag-free formation around free-falling test masses. Charging of the test masses by cosmic ray fluxes and solar energetic particles must be compensated by photons that contain more energy than the effective work function of gold ([Formula: see text]). The UV photons will be provided by AlGaN light emitting diodes, which must operate reliably for the duration of the mission. We have tested a large number (96 for dc and pulsed testing, more than 200 for all tests) of UV LEDs over a period of up to 600 days to characterize their performance over a wide range of operating conditions, assessing the lifetime performance under dc (1–[Formula: see text] drive current) and pulsed conditions (500–100 000 pulses per second) and temperatures ranging from [Formula: see text] to [Formula: see text]. Degradation of UV light output is faster at elevated temperatures and dc conditions. Preselection of LEDs based on initial spectral ratio of peak-to-midgap emission and ideality factor provides a positive correlation with subsequent reliability. The UV LEDs used for LISA will need to support 2 years of cruise and commissioning plus a 4-year baseline science mission.

Precision space inertial sensors used for satellite geodesy missions, tests of fundamental physics, and gravitational wave observation utilise UV photoemission to control the electric potential of free-falling test masses with respect to their surrounding electrode housings. Successful generation of photoelectrons requires UV light energies greater than the work function of the illuminated surface. To ensure bi-polar test mass charge control (positive and negative charge rates), the quantum yields of the test mass and electrode housing surfaces must be well-balanced. LISA Pathfinder used mercury vapour lamps at 254 nm to discharge the gold coated test mass by likely relying on contaminants to lower the work function of gold from its nominal value of 5.2 eV. The LISA gravitational wave mission plans to use UV light emitting diodes (LEDs) instead of mercury vapour lamps. These UV LEDs have a lower mass, higher power efficiency, and produce light at wavelengths below 240 nm. In this paper, we measure the quantum yields of several Au-coated surfaces over a range of UV wavelengths and environmental conditions, varying temperature, vacuum pressure, and measuring over long periods of time. We use these data to draw conclusions and make recommendations for the development and handling of precision space inertial sensors for LISA and for other missions in the future.