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Radar Aperture Synthesis Observations of Asteroids

Authors
Journal
Icarus
0019-1035
Publisher
Elsevier
Publication Date
Volume
111
Issue
2
Identifiers
DOI: 10.1006/icar.1994.1159

Abstract

Abstract We report results of Goldstone-VLA, radar aperture-synthesis observations of the mainbelt asteroids 324 Bamberga and 7 Iris and the near-Earth asteroids 1991 EE and 4179 Toutatis. Simultaneous resolution of echoes in both angle and Doppler frequency provide new constraints on the mainbelt asteroids' pole directions: Bamberga's spin vector is within 40° of the south ecliptic pole, and the twofold ambiguity in Iris' pole direction (P. Magnusson, 1989, in Asteroids II , pp. 1180-1190) is resolved in favor of the ecliptic coordinates λ = 15°, β = +25°. For Bamberga, monostatic and bistatic radar echoes and VLA thermal-emission measurements, also reported here, are consistent with radiometric estimates of Bamberga's size and with the hypothesis that the asteroid is overlain by a regolith having a porosity of ∼50%. Our near-Earth asteroid measurements required the development of new on-line VLA software that allows imaging of objects that are in the telescope's "near field." This software has been successfully tested on Toutatis at a distance of 0.06 AU and will be essential for VLA observations of Earth-approaching comets.

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