  Radio emission from Ultra-High Energy Cosmic Rays (UHECR) showers detected
after specular reflection off the Antarctic ice surface has been recently
demonstrated by the ANITA balloon-borne experiment. An antenna observing a
large area of ice or water from a mountaintop, a balloon or a satellite may be
competitive with more conventional techniques. We present an estimate of the
exposure of a high altitude antenna, which provides insight on the prospects of
this technique for UHECR detection. We find that a satellite antenna may reach
a significantly larger exposure than existing UHECR observatories, but an
experimental characterization of the radio reflected signal is required to
establish the potential of this approach. A balloon-borne or a mountaintop
antenna are found not to be competitive under any circumstances.
