Radar aperture synthesis observations of asteroids

de Pater, I., P. Palmer, D. L. Mitchell, S. J. Ostro, D. K. Yeomans, and L. E. Snyder (1994). Radar aperture synthesis observations of asteroids. Icarus 111, 489-502.

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 deg. 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 long = 15 deg., lat = +25 deg. 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.

Asteroid Radar Astronomy Publications