Radar Aperture Synthesis Observations of Asteroids
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.
- Publication:
-
Icarus
- Pub Date:
- October 1994
- DOI:
- 10.1006/icar.1994.1159
- Bibcode:
- 1994Icar..111..489D
- Keywords:
-
- Asteroids;
- Astronomy;
- Axes Of Rotation;
- Radio Observation;
- Rotation;
- Size (Dimensions);
- Surface Properties;
- Doppler Effect;
- Porosity;
- Radio Astronomy;
- Regolith;
- Spectrum Analysis;
- Thermal Emission