USNO Robotic Astrometric Telescope (URAT) phase 1

The U.S. Naval Observatory (USNO) will begin a new all-sky, astrometric survey in 2009. A new focal plane assembly has been funded in 2008 and is being built by Semiconductor Technology Associates (STA). It consists of 4 large CCDs (10.5k by 10.5k) and 4 smaller guide/focus chips mounted inside an LN2 dewar (G.Luppino) with the 300 mm clear aperture window serving also as filter for the 670 to 750 nm bandpass.

Phase 2 of this project requires a new 0.85m aperture telescope of which only the primary mirror has been delivered so far. The first phase of the USNO Robotic Astrometric Telescope (URAT) project, nicknamed "U-mouse", instead utilizes the existing, completely re-modeled USNO "redlens" astrograph to provide 28 square degrees sky coverage per single exposure with 0.905 arcsec/pixel resolution.

Test observing with the robotic telescope and a single 10k CCD will begin in January 2009 in Washington DC and delivery of the 4-shooter camera is expected in April 2009. Survey operations will be conducted from NOFS (northern) and

CTIO (southern hemisphere).

About 15-30 sky overlaps will be obtained from each site during 2 to 3 years of imaging to arrive at a catalog of positions, proper motions and parallaxes for stars in the R = 7 to 18 mag range with random errors of about 3 mas per coordinate for the 11 to 15 mag range, and systematic errors expected to be below 10 mas. Clocked anti-blooming is used to extend the dynamic range about 3 magnitudes beyond traditional saturation. A neutral density spot allows observations of naked eye stars.