NOAO >   Observing Info >   Approved Programs >   2004A-0053

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Proposal Information for 2004A-0053


PI: Norbert Zacharias, U.S. Naval Observatory, nz@usno.navy.mil
Address: AD, 3450 Massachusetts Ave. NW, Washington, DC 20392, USA

CoI: Marion I. Zacharias, Univ. Space Research Ass. (USRA), USNO
CoI: Theodore J. Rafferty, U.S. Naval Observatory (USNO)

Title: Extragalactic reference frame link of the UCAC project

Abstract: In January 1998 the US Naval Observatory CCD Astrograph (UCAC) project, a high accuracy, high density, astrometric survey, was started at CTIO. Observations of the southern hemisphere were completed and the instrument relocated to Flagstaff, AZ, in October 2001. Full sky coverage is expected by mid 2004. The second data release (UCAC2) was published in July 2003. The 2--fold overlap pattern and block adjustment techniques will allow for a strong link to extragalactic reference frame sources utilizing deep CCD frames obtained with the CTIO 0.9m, KPNO 2.1m and the KPNO WIYN 0.9m telescopes. With a small epoch difference between the deep and the astrograph observations and a total of about 500 sources, an unprecedented accuracy of the optical--radio reference frame link can be achieved. The rotation of the Hipparcos system with respect to the International Celestial Reference System (ICRS) will be determined by a factor of 2 more precisely than is currently known. Absolute position differences in the radio--optical centers of emission for individual sources on the 10 mas level will be derived. Outliers will indicate astrophysically interesting sources. The maintenance of a high accuracy radio--optical reference frame link is important for current and future high resolution imaging in all wavelengths, providing absolute positions (in an inertial frame) on the 10 mas level at any location in the sky. To our knowledge, this is the only major project in this area of research.


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