Investigation of the surface properties of the LISA Pathfinder witness samples and their implications on the LISA discharge system

We report a series of measurements of the surface properties on gold-coated samples of the LISA Pathfinder (LPF) test mass and electrode housing surfaces [1], that are the core of the Gravitational Reference System (GRS) for the space based gravitational wave observatory LISA (Laser Interferometer Space Antenna). This work gives insight into preparing the analysis plan for similar samples that will be produced together with the GRS prototypes models for LISA in the next years [2]. This study aims at understanding the dynamic changes of the surface properties and consolidate a strategy to maintain and, eventually, recover electron photoemission. Understanding if and, eventually, how surface properties could change will help optimize the manufacturing process, storage environment, and bake-out temperature of the gold-coated surfaces.