Observed asteroid surface area in the thermal infrared

TL;DR

This paper investigates how the thermal infrared observations of asteroids reveal that a small, highly shape-sensitive surface area contributes most of the thermal flux, enabling potential thermal mapping from unresolved data.

Contribution

It introduces a method to determine the fraction of an asteroid's surface contributing to thermal flux, highlighting the shape sensitivity of infrared observations.

Findings

Infrared observed surface areas are more fragmented than visible ones.

Small surface fractions dominate thermal emission at low thermal parameters.

Potential to create thermal inertia maps from unresolved infrared data.

Abstract

The rapid accumulation of thermal infrared observations and shape models of asteroids has led to increased interest in thermophysical modeling. Most of these infrared observations are unresolved. We consider what fraction of an asteroid's surface area contributes the bulk of the emitted thermal flux for two model asteroids of different shapes over a range of thermal parameters. The resulting observed surface in the infrared is generally more fragmented than the area observed in visible wavelengths, indicating high sensitivity to shape. For objects with low values of the thermal parameter, small fractions of the surface contribute the majority of thermally emitted flux. Calculating observed areas could enable the production of spatially-resolved thermal inertia maps from non-resolved observations of asteroids.