  This paper summarizes some cosmologically interesting measurements which are
uniquely possible in the hard X-ray band and presents a mission concept capable
of achieving them. The Present Epoch Plus mission will achieve a surface
brightness sensitivity of better than 1% per square degree in the 2-10 keV
band, and create a catalog of about 10^6 sources. About 160,000 extragalactic
sources are expected to be detected in the 2-10 keV band, providing an all sky
survey with nearly uniform selection effects 10 times deeper than exisiting or
planned surveys. The PEP concept can be achieved within the size and budgetary
constraints of a NASA Medium Explorer (MIDEX) mission.
