  The HADES experiment at GSI will soon provide data on the production and
properties of $\Delta$(1232) baryons from Au+Au reactions at 1.23 AGeV. Using
the UrQMD model, we predict the yield and spectra of $\Delta$(1232) resonances.
In addition we show that one expects to observe a mass shift of the
$\Delta$(1232) resonance on the order of 50 MeV in the reconstructable
$\Delta$(1232) mass distribution. This mass shift can be understood in terms of
late stage $\Delta$(1232) formation with limited kinetic energy. We show how
the mass shift can be used to constrain the kinetic decoupling temperature of
the system.
