Positions for the Outer Planets and Many of their Satellites. IV. FASTT Observations Taken in 1999–2000

This paper presents 1201 new equatorial positions taken in 1999–2000 for the outer planets Uranus, Neptune, and Pluto, as well as for 17 satellites of Jupiter–Neptune. Additional positions for Jupiter, Saturn, Uranus, and Neptune can be derived from the planetocentric orbits of their satellites given in this paper. All the positions were determined in the International Celestial Reference Frame (ICRF) from CCD observations taken with the Flagstaff Astrometric Scanning Transit Telescope (FASTT) using differential reductions. Accuracies of ±0 08 to ±0 28 were achieved, depending on the signal-to-noise ratio observed for each object. When new and older FASTT positions are compared with modern Jet Propulsion Laboratory (JPL) ephemerides, there is usually good agreement (±0 1 and often much better) between theory and observation. In particular, the agreement with DE405 for the planets Jupiter–Pluto is always better than ±0 05, when results are averaged over several years. Exceptions include the outer satellites of Jupiter (Elara and Pasiphae) and two satellites of Uranus (Titania and Oberon), whose ephemerides probably need improvement.