Radar Observations of 2000 DP107, Sep 2000

Asteroid 2000 DP107 was discovered by MIT's Lincoln near-earth asteroid research (LINEAR) search programme on Feb 29, 2000. This object approached the Earth at a distance of 0.048 AU on Sep 17--21, and it was observed at Goldstone by Margot, Benner, Jurgens and Ostro on Sep 22 and on Sep 23. The first night of continuous-wave observations provided spectra with very unusual signatures.

The spectra show a broadband echo about 30 Hz wide, which corresponds to a spin period of about 3 hours for equatorial view. Superposed on the spectrum is a strong narrowband echo about 1 Hz wide. Such a narrow spike could in principle be related to a highly reflective region on the asteroid or to the specular return of a facet oriented normal to the line of sight. Alternatively, it could represent the signature of a second, distinct object, with a smaller size or longer rotation period than the primary.

On Sep 23, our CW spectra showed that the spike had migrated to positive frequencies, ruling out the possibility of a specular echo from a flat region. This inference was further supported by the fact that the ratio of power in the same sense circular polarization (SC) to power in the opposite sense circular polarization (OC) remains relatively constant across the band. Specular returns would normally contain very little power in the SC component.

Definite evidence for the two-component nature of the system was provided by subsequent imaging at 75 m range resolution and 1 Hz frequency resolution. The images show a clear separation between two distant scattering centers, and and show that the distance between the primary and secondary increased over time.

Imaging data, 75 m range resolution, 5 Hz frequency resolution

Imaging data, 75 m range resolution, 1 Hz frequency resolution

Sep 22 CW data

Sep 23 CW data