Asteroid Diameters and Albedos from NEOWISE Reactivation Mission Years Six and Seven

TL;DR

This paper reports diameters and albedos for over 1800 asteroids observed by NEOWISE during its sixth and seventh years, highlighting the uncertainties and orbital characteristics of these objects.

Contribution

It provides new thermal measurements and analysis of asteroid orbits from NEOWISE Reactivation data, expanding the asteroid database and insights into their orbital distributions.

Findings

Approximately 30% uncertainty in NEO diameter estimates compared to cryogenic data.

NEOWISE discovered NEOs on orbits with perihelia far from the ecliptic.

Total of 1845 unique NEOs characterized by NEOWISE to date.

Abstract

We present diameters and albedos computed for the near-Earth and Main Belt asteroids observed by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft during the sixth and seventh years of its Reactivation mission. These diameters and albedos are calculated from fitting thermal models to NEOWISE observations of $199$ NEOs and $5851$ MBAs detected during the sixth year of the survey, and $175$ NEOs and $5861$ MBAs from the seventh year. Comparisons of the near-Earth object diameters derived from Reactivation data with those derived from the WISE cryogenic mission data show a $\sim30\%$ relative uncertainty. This larger uncertainty compared to data from the cryogenic mission is due to the need to assume a beaming parameter for the fits to the shorter wavelength data that the Reactivation mission is limited to. We also present an analysis of the orbital parameters of the Main Belt asteroids that have been discovered by NEOWISE during Reactivation, finding that these objects tend to be on orbits that result in their perihelia being far from the ecliptic, and thus missed by other surveys. To date, the NEOWISE Reactivation survey has provided thermal fits of $1415$ unique NEOs. Including the mission phases before spacecraft hibernation increases the count of unique NEOs characterized to $1845$ from WISE's launch to the present.