Near-Earth Asteroid CW Radar Observations at Arecibo Observatory 1998-2016

Near-Earth asteroids (NEAs) are a diverse population of objects derived from the main asteroid belt with a wide range of sizes, shapes, compositions and biases in how efficiently they are delivered to near-Earth space. Radar observations provide a powerful tool for observing and characterizing NEAs that pass within a volume of space accessible to the Arecibo telescope and close to Earth (typically less than 0.1 au). This set of NEAs has different selection biases than many other surveys, and so the distribution of properties provides a new perspective. Continuous wave (CW) observations of NEAs provide initial estimates of apparent rotation rate and radar reflectivity as well as astrometry for orbit refinement. Observations at 2380 MHz (12.6 cm wavelength) between 1998 and June 2016 have been analyzed in a uniform and consistent way to provide an assessment of the radar properties of over 400 NEAs measured at the Arecibo Observatory. We confirm the findings of Benner et al. (2008) that high polarization ratios are found primarily among E-type and V-type objects. We calculate the radar cross-section and radar albedo when the geometric cross-section is known. Uncertainties in the measured radar properties have been evaluated for both the thermal and self-noise contributions. We will present a summary of the distribution of radar properties of NEAs and trends with size, shape, taxonomy and discuss the implications for understanding NEAs.

1. Benner, L.A.M, et al. (2008) Icarus 198 294-304.