  In this work, we present expressions for radiative heat transfer between
pairs of spheres in a linear chain and between individual spheres and their
environment. The expressions are valid for coated spheres of arbitrary size,
spacing, and isotropic optical properties. The spheres may be small and
closely-spaced, which violates the assumptions foundational to classical
radiative transfer. We validate our results against existing formulations of
radiative heat transfer, namely the thermal discrete dipole and boundary
element methods. Our results have important implications for the modeling and
interpretation of near-field radiative heat transfer experiments between
spherical bodies.
