Astronomy and Astrophysics – Astronomy
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009iau...261.0605e&link_type=abstract
American Astronomical Society, IAU Symposium #261. Relativity in Fundamental Astronomy: Dynamics, Reference Frames, and Data Ana
Astronomy and Astrophysics
Astronomy
Scientific paper
As Viking Lander range measurements became available in the late 1970's, both the MIT and the JPL ephemeris groups noted that the ability to predict future range measurements from the data in hand was poor. In the early 1980's J.G. Williams at JPL recognized that asteroids with long term apparent resonances with the orbit of Mars could induce large orbital perturbations, biasing the resulting ephemeris parameters. As a result, modern solar system ephemeris solutions typically include the effects of dozens or even hundreds of asteroids. Despite this modeling, the sort of prediction errors seen with Viking are still observed as new data are acquired, indicating that unmodeled asteroid perturbations are still a serious source of error, including in the estimation of relativistic parameters.
We have used numerical integrations to examine the effects of perturbations from asteroids beyond those considered by the JPL and St. Petersburg groups, with results including
- The Trojan and Hilda asteroids (1:1 and 2:3 Jupiter resonances) have a significant influence on the orbits of Mars and Jupiter, and will bias the apparent mass of the Sun, and induce observable errors in the position of Mars. Conversely, existing and planned measurements may be able to provide useful constraints on the bulk density of the Trojans.
- Outer solar system asteroids will have observable effects on the motions of Jupiter and Saturn.
- Most asteroids are in a number of apparent resonances (there are over 1000 asteroids in an apparent 1:1 resonance with Ceres, for example), and these will grossly perturb the orbits of even the largest asteroids, and bias the dynamical estimates of their masses. These biases may be detectable for Ceres and Vesta by the Dawn spacecraft.
- Even relatively small asteroids can produce observable perturbations if they come close to one of inner planets.
Bills Bruce
Eubanks Thomas Marshall
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