NASA's Astrometric Telescope Facility

Astrometric effects of non-uniform telescope throughput

In real telescopes, the optical parameters evolve with time, and the degradation is often not uniform. This introduces variations in the image profile and therefore photo-centre displacements which, unless corrected, may result in astrometric errors. The effects induced on individual telescopes and interferometric arrays are derived by numerical implementation of a range of cases. The results a...

Results of the Guide-2 telescope testbed for the SIM Light Astrometric Observatory

The SIM Lite Astrometric Observatory is to perform narrow angle astrometry to search for Earth-like planets, and global astrometry for a broad astrophysics program, for example, mapping the distribution of dark matter in the Galaxy. The new SIM Lite consists of two Michelson interferometers and one star tracking telescope. The main six-meter baseline science interferometer observes a target sta...

Astrometric Monitoring of Stellar Orbits at the Galactic Center with a Next Generation Large Telescope

We show that with a Next Generation Large Telescope one can detect the accelerated motions of ∼ 100 stars orbiting the massive black hole at the Galactic center. The positions and velocities of these stars will be measured to astrometric and spectroscopic precision several times better than currently attainable enabling detailed measurements of the gravitational potential in the neighborhood of...

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Astrometric surveys

Astrometric surveys are a basic tool for galactic astronomy: they provide the only distance determination without assumption about the observed object as well as two components of the space velocity. A large number of stars, observed in a systematic way, yield to an unbiased sampling of the Galaxy and, for the most accurate surveys, of the brightest parts of Local Group galaxies, at larger and ...