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Microprecision interferometer test bed: first stabilized stellar fringes

This paper presents initial results that demonstrate the end-to-end operation of the Micro- Precision Interferometer (MPI) testbed. The testbed is a full-scale model of a future space- based interferometer, containing all the spacecraft and support systems necessary to perform an astrometric measurement. The primary objective of the testbed is to provide an end-to-end problem to evaluate and integrate new interferometer technologies, such as vibration isolation, structural quieting, active optics, and metrology systems. This paper shows initial testbed functionality in terms of the ultimate performance metric: stabilization of stellar fringes (from a pseudo star). The present incarnation of the evolving testbed uses a fringe tracker and pointing control subsystem to stabilize the fringe position to the 72 nm (RMS) level in the presence of the ambient laboratory seismic noise environment which is a factor of 10 higher than that expected on-orbit. These encouraging preliminary results confirm that the MPI testbed provides an essential link between the extensive ongoing ground-based interferometer technology development activities and the technology needs of future spaceborne interferometers.