Charge Management System for the LISA Gravitational Reference Sensor using UV LED-Based Charge Control via the Photoelectric Effect

The LISA observatory, a gravitational wave detector in space, consists of three drag-free spacecraft flying in equilateral triangle formation governed by their inertial reference sensors: a test mass (TM) in free fall surrounded by an electrode housing. Critical to operation is maintaining a force noise level below a fN/Hz1^/2 within the mHz gravitational wave frequency band. Cosmic rays and solar energetic particles accrue charge on the TM, producing disturbance forces that must be mitigated. TM electrical charge can be controlled in a non-contact manner using UV light via the photoelectric effect. NASA's contribution to the ESA mission includes the technology development for a Charge Management System (CMS), tasked to maintain the potential of the TM relative to its housing to below the required level via fiber-coupled UV LEDs. A charge management device (CMD) is being developed to control UV LEDs in both a continuous and pulsing manner via user-specified inputs designed for integration with the LISA science instrument. Also, over 100 UV LEDs are being tested for space performance and lifetime integrity for the projected 10-year long mission. Discussion will include the status of the CMD development and the preliminary results from UV LED testing.

NASA LISA CMS #80NSSC17K0277.