Two technical improvements will be made to the Keck Interferometer that will allow unprecedented astrometric observations of the galactic center. The first improvement is to allow fainter science objects to be observed with the Keck Interferometer by implementing a phase referencing mode that uses a bright nearby star to provide the piston correction. (The piston correction accounts for the difference in phase fluctuations that occur along the optical axes of the interferometer elements). The second improvement is to implement an astrometric capability with an accuracy of 30 microarcseconds. The significant new science capabilities of the Keck Interferometer will be available to a broad community of astronomers.
