PI: Norbert Zacharias, U.S. Naval Observatory, firstname.lastname@example.org
Address: AD, 3450 Mass. Ave. NW, Washington, DC 20392, USA
CoI: Greg Hennessy, USNO / AD
CoI: Kenneth J. Johnston, USNO / SD
Title: Photometric monitoring of optically bright QSOs
Abstract: The goal of this observing program is to select suitable, compact, optically bright QSOs for a future astrometric celestial reference frame which will be established by missions like SIM, GAIA, OBSS or MAPS. Candidates have been pre-selected from the Veron-Cetty catalog and digital sky images, and do not need to be radio-loud. This program is required for our accepted key science project with the Space Interferometry Mission (SIM). These sources are required to establish an inertial reference frame for SIM global astrometric data, else no absolute proper motions and parallaxes can be obtained. SIM is a pointed mission and only a very limited number of targets can be observed. SIM observing time also scales with brightness of the targets ranging from about 30 second to many hours to achieve nominal mission accuracy. We propose to photometrically monitor a large sample (about 300 all-sky) of quasars in BVRI. Accurate brightness and color information is vital for scheduling SIM observations and optimize scientific return. The CCD images with a resolution better than the digital sky images will also be used to check on optical structure. A future extension of this program will repeat the photometric observations over several years to study variability. A complimentary observing program in the Northern Hemisphere has already started using the USNO 1 meter telescope in Flagstaff, AZ.
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