The U.S. Naval Observatory pole-to-pole catalog: W2$_{{\rm J}00}$

Abstract

Between the years 1985 and 1996 the U.S. Naval Observatory (USNO), using two transit circles, one located in Washington, DC (U.S.A.) and the other in Blenheim, New Zealand, conducted an ambitious program of absolute observations of positions of celestial objects completely covering both hemispheres. Over 737 000 individual observations were made, primarily of the International Reference Stars (IRS) and FK5 stars, as well as all the major planets (except Pluto) and thirteen minor planets. This included some 55 000 observations of day-time objects including the Sun, Mercury, Venus, and Mars. The original objective was to form a traditional, all-sky catalog of absolute star positions which could be firmly linked to the dynamical system. However, with the success of the Hipparcos project and the adoption of the ICRF as the celestial reference frame, the primary focus of the pole-to-pole program changed. The stellar positions have been differentially reduced to the system of Hipparcos and these were used to tie the planetary observations into the ICRF. Thus the program has resulted in a body of high quality observational data (average standard deviation of a mean position of about 75 mas) that will provide important input for the production of ICRF-based ephemerides. This is particularly true for the outer and minor planets.