HST FGS astrometry — the value of fractional millisecond of arc precision

摘要

In a few years astrometry with the venerable combination of Hubble Space Telescopeand Fine Guidance Sensor will be replaced by SIM, Gaia, and long-baseline interferometry. Untilthen we remain a resource of choice for sub-millisecond of arc precision optical astrometry. Asexamples we discuss 1) the uses which can be made of our parallaxes of Galactic Cepheids, and2) the determination of perturbation orbital elements for several exoplanet host stars, yieldingtrue companion masses.