  We present a precise measurement of downward-going albedo proton fluxes for
kinetic energy above $\sim$ 70 MeV performed by the PAMELA experiment at an
altitude between 350 and 610 km. On the basis of a trajectory tracing
simulation, the analyzed protons were classified into quasi-trapped,
concentrating in the magnetic equatorial region, and un-trapped spreading over
all latitudes, including both short-lived (precipitating) and long-lived
(pseudo-trapped) components. In addition, features of the penumbra region
around the geomagnetic cutoff were investigated in detail. PAMELA results
significantly improve the characterization of the high energy albedo proton
populations at low Earth orbits.
