The SIM Grid Star Program

The SIM Grid is composed of 1302 stars distributed over the entire sky, and will be used to establish a reference frame for global astrometric observations. The potential candidates for the Grid were chosen to be photometrically stable K-type giants. Candidates were chosen by a rank-order metric, based on such observables as visual magnitude, metallicity, J-K color attributed to K giant stars, and also distance. Three observatories have been contracted to measure the radial velocities of these candidate stars. The RV measurements are made in an effort to narrow candidate stars to those without suspected binarity, pulsation, or other forms of non-regularity. We present a synposis of the SIM Grid Star Program, each observatory and their instrumentation.