Herein we report on the development, sensing and control and our first results with the Vacuum Nuller Testbed to realize
a Visible Nulling Coronagraph (VNC) for exoplanet coronagraphy. The VNC is one of the few approaches that works
with filled, segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA
telescopes and could be flown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center
(GSFC) has a well-established effort to develop VNC technologies, and has developed an incremental sequence of VNC
testbeds to advance this approach and the enabling technologies associated with it. We discuss the continued
development of the vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated
testbed that operates under closed-loop control within a vacuum chamber. It will be used to achieve an incremental
sequence of three visible-light nulling milestones with sequentially higher contrasts of 108, 109, and ideally 1010 at an
inner working angle of 2*λ/D. The VNT is based on a modified Mach-Zehnder nulling interferometer, with a "W"
configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic
phase shifters. We discuss the initial laboratory results, the optical configuration, critical technologies and the null
sensing and control approach.