  Cosmic ray antiprotons can originate from dark matter annihilating into
quarks that subsequently decay into antiprotons. Evaporation of primordial
black holes also can produce a significant antiproton flux. Since the spectrum
of secondary antiprotons from cosmic ray interactions peaks at ~ 2 GeV and goes
down sharply at lower energy, there is a window at energies < 1 GeV in which to
look for excess antiprotons as a signature of these exotic antiproton sources.
However, in the vicinity of the Earth low energy particles are strongly
modulated by the solar wind, which makes any analysis ambiguous. The adverse
effects of the solar wind can be avoided by placing a low energy antiproton
spectrometer aboard an interstellar probe. The theoretical predictions are
reviewed and the preliminary design of a light-weight, low-power instrument to
make the measurements and a summary of the anticipated results are given in
this paper.
