  Ground state rotational lines of H2 are good temperature probes of moderately
hot (200-1000 K) gas. The low A-values of these lines result in low critical
densities while ensuring that the lines are optically thin. ISO observations of
H2 rotational lines in PDRs reveal large quantities of warm gas that are
difficult to explain via current models, but the spatial resolution of ISO does
not resolve the temperature structure of the warm gas. We present and discuss
high spatial resolution observations of H2 rotational line emission from the
Orion Bar.
