ExploreNEOs I: Description and first results from the Warm Spitzer NEO Survey

TL;DR

The ExploreNEOs project uses Warm Spitzer observations to derive physical properties of approximately 700 NEOs, revealing a broad albedo distribution and insights into their compositional diversity and surface aging.

Contribution

This paper introduces the ExploreNEOs survey methodology, presents initial results from 101 NEOs, and discusses the implications for understanding NEO composition and surface evolution.

Findings

Broad albedo distribution indicates diverse compositions.

Smaller NEOs tend to have higher albedos.

Larger NEOs are generally darker, suggesting older, more weathered surfaces.

Abstract

We have begun the ExploreNEOs project in which we observe some 700 Near Earth Objects (NEOs) at 3.6 and 4.5 microns with the Spitzer Space Telescope in its Warm Spitzer mode. From these measurements and catalog optical photometry we derive albedos and diameters of the observed targets. The overall goal of our ExploreNEOs program is to study the history of near-Earth space by deriving the physical properties of a large number of NEOs. In this paper we describe both the scientific and technical construction of our ExploreNEOs program. We present our observational, photometric, and thermal modeling techniques. We present results from the first 101 targets observed in this program. We find that the distribution of albedos in this first sample is quite broad, probably indicating a wide range of compositions within the NEO population. Many objects smaller than one kilometer have high albedos (>0.35), but few objects larger than one kilometer have high albedos. This result is consistent with the idea that these larger objects are collisionally older, and therefore possess surfaces that are more space weathered and therefore darker, or are not subject to other surface rejuvenating events as frequently as smaller NEOs.