LISA Charge Management Device: design and performance

Abstract The Laser Interferometer Space Antenna (LISA) mission will be the first space-based gravitational wave observatory. Observing signals in the mHz band requires maintaining test masses (TMs) in near perfect free fall. Charge accumulation on the TMs from cosmic rays and solar energetic particles contributes to electrostatic acceleration noise and must be controlled to keep the TM potential within ± 70 mV. This paper details the design and performance testing of the charge management device (CMD), which employs UV light-emitting diodes centered at 250 nm to control the TM charge. The CMD supports two illumination modes: a DC mode inherited from LISA Pathfinder and a novel pulsed mode that synchronizes UV emission with the gravitational reference sensor capacitive sensing injection voltages applied to the TM. Performance testing of the CMD hardware was conducted under relevant environmental conditions following technology readiness level 6 qualification guidelines. The UV light unit successfully met the repeatability (within 1% over 15 days) and spectral emission profile requirements. The system demonstrated compliance with low power (10 pW) and DC high power (500 nW) requirements, as well as all noise performance requirements for relative power ( < 0.1 Hz − 1 / 2 ) and relative phase ( < 7 mrad Hz − 1 / 2 ) stability. The pulsed high power requirement (125 nW) was partially met and will be addressed in future design iterations. These results demonstrate that the CMD provides stable and repeatable UV power control over the dynamic range required for LISA charge management, limiting discharge induced charge fluctuations and supporting compliance with the electrostatic acceleration noise allocation for the gravitational reference system. The next development phase will implement Engineering Test Unit design updates to further mature the CMD architecture toward flight readiness.