NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos

TL;DR

The NEOWISE reactivation mission's third year provided thermal infrared data leading to asteroid diameter and albedo measurements, significantly increasing the number of characterized near-Earth objects and confirming measurement accuracy.

Contribution

This paper presents the third-year asteroid diameters and albedos from NEOWISE, expanding the dataset and validating previous measurements with improved accuracy.

Findings

Diameter measurements agree within 26% for NEOs

Diameter measurements agree within 17% for MBAs

Total characterized NEOs increased to 541

Abstract

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) reactivation mission has completed its third year of surveying the sky in the thermal infrared for near-Earth asteroids and comets. NEOWISE collects simultaneous observations at 3.4 um and 4.6 um of solar system objects passing through its field of regard. These data allow for the determination of total thermal emission from bodies in the inner solar system, and thus the sizes of these objects. In this paper we present thermal model fits of asteroid diameters for 170 NEOs and 6110 MBAs detected during the third year of the survey, as well as the associated optical geometric albedos. We compare our results with previous thermal model results from NEOWISE for overlapping sample sets, as well as diameters determined through other independent methods, and find that our diameter measurements for NEOs agree to within 26% (1-sigma) of previously measured values. Diameters for the MBAs are within 17% (1-sigma). This brings the total number of unique near-Earth objects characterized by the NEOWISE survey to 541, surpassing the number observed during the fully cryogenic mission in 2010.