The Guide Star Catalog. II. Photometric and Astrometric Models and Solutions

The models, algorithms, and procedures used to calibrate the all-sky set of objects in the Guide Star Catalog (GSC) are discussed. The role of the GSC in the Hubble Space Telescope program is reviewed. The photometric reductions and error analysis are described. Consideration is given to the photometric agreement between the GSC and the Guide Star Photometric Catalog, the internal consistency of GSC photometry in plate-overlap regions, and the agreement of the GSC with photometry from other photoelectric surveys. The astrometric reductions and error analysis are also examined, including results from experiments in an astrometric test region, the agreement of the GSC with other reference catalogs, the internal consistency of GSC astrometry in the plate-overlap regions, and the agreement of the GSC with astrometry from independent surveys. The photometric and astrometric solutions for the individual plates are described.