  One of the main impacts of the JEM-EUSO mission will come from its
unprecedented exposure. This feature creates, for the first time in the field,
the possibility of studying individual UHECR sources. However, the intrinsic
characteristics of the sources and the injection mechanism, as well as the
presence of intervening magnetic fields, present challenges to the
identification of isolated sources and to the extraction of their relevant
spectral information from the data. We discuss here these aspects in a
quantitative way and give an overview of what can be achieved in this regard
under different astrophysical scenarios.
