Goldstone and Arecibo Radar Images of Near-Earth Asteroid 2014 HQ124
Abstract
2014 HQ124 was discovered by the NEOWISE mission on 2014 April 23, about six weeks before the asteroid approached within 0.0084 au on June 8. Prior to the encounter, A. K. Mainzer used NEOWISE data and a thermal model to estimate a diameter of 330 +- 90 m. The NEOWISE data and photometry obtained by J. T. Pollock yielded a rotation period of ~20 h and a lightcurve amplitude of 0.8 mag. The close approach, diameter, and slow rotation indicated that this object would provide an outstanding opportunity for radar imaging, characterization, and orbit refinement. We observed 2014 HQ124 on June 8 and 10 with at Goldstone, Arecibo, and the Very Long Baseline Array (VLBA). We conducted monostatic radar imaging at X-band (8560 MHz, 3.5 cm) with the 70 m DSS-14 antenna and at S-band (2380 MHz, 13 cm) with Arecibo; bistatic X-band imaging using DSS-14 to transmit and Arecibo and the 34 m DSS-13 antenna to receive; and S-band radar speckle observations to constrain the spin state using Arecibo to transmit and the Pie Town, Los Alamos, Ft. Davis, and Kitt Peak VLBA facilities to receive. Radar astrometry improved the orbit significantly and increased the interval of reliable orbit estimation by a factor of two to ~900 years. The images achieve a resolution of 3.75 m x 0.00625 Hz and provide some of the most detailed radar views obtained for any near-Earth object. 2014 HQ124 is elongated, angular, and bifurcated with a long axis of at least 400 m. The asteroid has a large concavity, possible ridges, and small-scale features including radar-bright spots that are candidates for boulders. The larger lobe has a narrow, sinuous, ~100-m-long radar-dark feature that may be a scarp or perhaps a fault. These observations were the first test of new data taking equipment at Arecibo that can acquire images at 3.75 m resolution, which is twice as fine as the highest range resolution that Arecibo can achieve with monostatic observations. Receiving echoes at Arecibo using transmissions from Goldstone also boosts the signal-to-noise ratio by a factor of five relative to monostatic Goldstone observations and is ideal for resolving very close and/or small near-Earth objects with slow spin states.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #46
- Pub Date:
- November 2014
- Bibcode:
- 2014DPS....4640901B