NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos

TL;DR

The NEOWISE mission's second year of data collection has provided new measurements of asteroid sizes and reflectivity, significantly expanding the dataset for near-Earth and other asteroids with verified accuracy.

Contribution

This paper presents the second-year diameters and albedos of over 8,000 asteroids, including 207 near-Earth objects, with improved measurement accuracy and validation against other techniques.

Findings

84% of near-Earth asteroids lacked previous measurements

Diameters and albedos are accurate within ±20% and ±40% respectively

NEOWISE favors discovering large, low-albedo near-Earth objects

Abstract

The Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) mission continues to detect, track, and characterize minor planets. We present diameters and albedos calculated from observations taken during the second year since the spacecraft was reactivated in late 2013. These include 207 near-Earth asteroids and 8,885 other asteroids. $84\%$ of the near-Earth asteroids did not have previously measured diameters and albedos by the NEOWISE mission. Comparison of sizes and albedos calculated from NEOWISE measurements with those measured by occultations, spacecraft, and radar-derived shapes shows accuracy consistent with previous NEOWISE publications. Diameters and albedos fall within $ \pm \sim20\%$ and $\pm\sim40\%$, 1-sigma, respectively, of those measured by these alternate techniques. NEOWISE continues to preferentially discover near-Earth objects which are large ($>100$ m), and have low albedos.