[Previous] | [Session 41] | [Next]
J.L. Hilton (U.S. Naval Observatory)
Since the 2000 edition of the Astronomical Almanac, the ephemerides for the first four asteroids, Ceres, Pallas, Juno, and Vesta, have been based on the USNO/AE98 (Hilton, J.L. 1999, Astron. J., 117, 1077-1086). Beginning with the 2003 edition, the Astronomical Almanac will replace the current bi-daily ephemerides of the first four asteroids with daily ephemerides for 60 days either side of opposition of these asteroids and the other 11 asteroids included in USNO/AE98. In addition to the ephemerides of these asteroids, the Astronomical Almanac will print the elements, date of opposition, and approximate declination at opposition of a total of 93 asteroids. These asteroids were chosen because they are particularly bright (m < 11 at mean opposition or m < 12 if d > 200 km) and, generally, large. The asteroids in this selection include the 15 in USNO/AE98 and an additional 78 whose ephemerides, tentatively titled USNO/AE2001, are currently under development. Analysis of the residuals of the preliminary ephemerides show significant systematic errors for at least four and, perhaps, as many as 13 of the 78 asteroids. The most likely source of these systematic errors is perturbation by asteroids unmodeled in the preliminary ephemerides. Thus, if the perturbing asteroids can be identified, it may be possible to add to the number of large asteroids for which masses have been determined.
The author(s) of this abstract have provided an email address for comments about the abstract: jhilton@aa.usno.navy.mil