  We present calculations of dilepton and photon spectra for the energy range
$E_{\text{lab}}=2-35$ $A$GeV which will be available for the Compressed
Baryonic Matter (CBM) experiment at the future Facility for Anti-Proton and Ion
Research (FAIR). The same energy regime will also be covered by phase II of the
Beam Energy Scan at the Relativistic Heavy-Ion Collider (RHIC-BES).
Coarse-grained dynamics from microscopic transport calculations of the
Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is used to
determine temperature and chemical potentials, which allows for the use of
dilepton and photon-emission rates from equilibrium quantum-field theory
calculations. The results indicate that non-equilibrium effects, the presence
of baryonic matter and the creation of a deconfined phase might show up in
specific manners in the measurable dilepton invariant mass spectra and in the
photon transverse momentum spectra. However, as the many influences are
difficult to disentangle, we argue that the challenge for future measurements
of electromagnetic probes will be to provide a high precision with
uncertainties much lower than in previous experiments. Furthermore, a
systematic study of the whole energy range covered by CBM at FAIR and RHIC-BES
is necessary to discriminate between different effects, which influence the
spectra, and to identify possible signatures of a phase transition.
