  In this effort, we demonstrate the performance of a highly stable time
reference for the proposed Black Hole Explorer (BHEX) mission, a space-based
extension to the Event Horizon Telescope (EHT) Very Long Baseline
Interferometry (VLBI) project. This precision timing system is based on the use
of a space-qualified, ultra-low noise laser developed as part of the Laser
Interferometer Space Antenna (LISA) mission as the timing reference, and an
optical frequency comb to transfer the stability of this laser to the microwave
regime for instrumentation use. We describe the implementation of this system
and experimental setup to characterize the stability performance. We present
the results of this experiment that demonstrate the performance of this system
meets requirements for the BHEX mission.
