High Definition Astrometry

High Definition Astrometry (0.1 - 1.0 micro-arcseconds) will open a new window into neighboring planetary systems. For the first time, the realm of temperate terrestrial worlds will be explored. This includes Earth Analogs, thereby allowing the value of eta-Earth to be directly determined, without resort to extrapolation. High Definition Astrometry will provide a means to confirm the existence of Radial Velocity (RV) planets while, at the same time, measuring true mass, along with orbit inclination and radius, i.e., system architecture. Planetary systems not amenable to RV search, such as those in a "face-on" orientation, will be surveyed for the first time. Extreme Precision Astrometry is not only useful, but is essential to the future of exoplanet research.