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M. Granvik, J. Virtanen, K. Muinonen (Univ. Helsinki), L. Allen (Univ. British Columbia), V. Meadows, B. Bhattacharya (Spitzer Science Center, Caltech), M. Delbo, A. Cellino (Univ. Torino), E. Tedesco (Space Science Center, Univ. New Hampshire), D. Davis (Planetary Science Institute), J. D. Giorgini (Jet Propulsion Laboratory)
Observations with the ESO Very Large Telescope and the Canada-France-Hawaii Telescope were obtained in January 2004, to provide ground-based follow-up for the Spitzer First Look Survey Ecliptic Plane Component (Meadows et al., 2004, AJSS 154). The goal is to estimate the albedo and size distributions of main-belt asteroids (MBAs) having sizes well below the current completeness limit, by obtaining nearly-simultaneous optical and infrared observations. Due to a substantial parallax effect which is a consequence of the comparatively large distance between the Spitzer telescope (on an Earth-like heliocentric orbit) and the ground-based observatories, the nearly-simultaneous apparent coordinates of the same objects detected from space and from ground are different. Moreover, since the number of observations per object per night is extremely limited (2--4 per telescope), linking separate detections is a nontrivial task. For this purpose, we use a new method (Granvik and Muinonen, 2005, Icarus, in press) specifically suited to this problem. To be able to compute the size and albedo of an observed MBA using the radiometric technique, we need to know the Sun-asteroid and telescope-asteroid distances at the observation dates. As most of the detected asteroids have never been observed before, the distances and their uncertainty estimates can only be based on the limited amount of data obtained within this project. A rigorous distance analysis of the found linkages by means of statistical ranging (Virtanen et al., 2001, Icarus 154) is the final step of the orbit computation part of the project. We present here the preliminary results of our analysis, including the statistics and accuracy of the resulting orbital elements.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.