Norbert Zacharias (USNO), Marion Zacharias (USRA)
Reference URL: http://aries.usno.navy.mil/ad/ucac/ucac-s.html
The USNO CCD Astrograph Catalog South (UCAC-S) project is a high precision astrometric survey of the entire southern hemisphere for the 7-16 magnitude range (610/60 nm), aiming at an accuracy of 20 mas for 8-14m stars. The ACT and the Hipparcos and Tycho Catalogues are used as reference, supplemented by an extragalactic link program. A 4kx4k CCD is used at the back-end of a 5-element, 0.2 meter aperture astrograph. A 2-fold overlap pattern of 43,839 fields will produce 1.7 tera-bytes of compressed raw data. The project started in January 1998 at CTIO and is scheduled for 2 years to complete. A simple compression method (I*2 to I*1) is used for the CCD frame data throughout the system including storage on tapes and CD-ROMs. A relatively high operating temperature (-18C) is used to minimize systematic positional errors depending on magnitude. On-line reductions are performed immediately after a pair of frames has been acquired to obtain quality control statistics. Complete reductions are performed the next day. Customized Fortran routines are used throughout. ASCII files and a strict nomenclature are used for auxiliary data handling, while large astrometric data files utilize unformatted direct access structures. Raw data reduction is based on Software for Analyzing Astrometric CCDs (SAAC). The Hamburg Block Adjustment Program Package (HBAPP) previously used for photographic astrometry has been adopted for this project, including a variety of PGPLOT visualizations. Block adjustment procedures will be used for the final astrometric reduction, solving for about 250,000 parameters simultaneously.