Next Generation Instrumentation for the Very Large Telescope Interferometer

The scientific capabilities of the VLT Interferometer can be substantially enhanced through new focal-plane instruments. Many interferometric techniques-astrometry, phase-referenced imaging, nulling, and differential phase measurements-require control of the phase to less than or similar to1 rad; this capability will be provided at the VLTI by the PRIMA facility. Phase-coherent operation of the VLTI will also make it possible to perform interferometry with spectral resolution up to Rsimilar to100,000 by building fiber links to the high-resolution spectrographs UVES and CRIRES. These developments will open new approaches to fundamental problems in fields as diverse as extrasolar planets, stellar atmospheres, circumstellar matter, and active galactic nuclei.