  A solid observational characterization of cluster regions around the virial
radius would allow us to improve considerably our understanding of the physics
of galaxy clusters as a whole: sadly current and planned experiments will not
allow us to study these regions. Unbeknownst to most but not all, the
development of an experiment sensitive to cluster outer regions could be
achieved with currently available technology, with no need for breakthroughs.
Amongst the major factors that will decide whether and when such an experiment
will be flown are the awareness of the cluster community of the importance of
such a mission and its determination in supporting it.
