Apparent Yield Measurements using a LISA-like Gravitational Reference Sensor and the University of Florida Torsion Pendulum
Space-based gravitational missions rely on the pure free-fall of isolated test masses (TM). Charge build-up on these TMs will incur spurious electrostatic forces which ultimately spoil the high-precision measurements necessary to reach the required mission performance.
Apparent Yield Measurements using a LISA-like Gravitational Reference Sensor and the University of Florida Torsion Pendulum
credit
John Siu, Dr. Stephen Apple, Brij Patel, Corey Richardson, Dr. Simon Barke, Dr. Lea Bischof, Dr. Peter Wass, Dr. John Conklin
Previous missions like Gravity Probe B and LISA Pathfinder have used photoelectron emission from ultraviolet (UV) illumination as a method of contactless electrostatic charge control. In LISA, the Charge Management Device (CMD) developed by the University of Florida (UF), which utilizes UV light-emitting diodes (LED) as light sources, is employed for this purpose. In order to fully understand the discharging performance of our UV-LED-based CMD, it is crucial to characterize the charge behavior of these test masses in their electrode housings. We present measurements of the net discharge current per photon injected into the system, or apparent yield (AY), for a LISA-like test mass and electrode housing incorporated into the UF torsion pendulum facility. Measurements were made using UV light illumination schemes relevant to the LISA mission. Empirical results from both synchronized-pulsed light and quasi-DC light are presented, which are then also used in a simulation of this process in its entirety within the COMOSL Multiphysics modeling software.