  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.
