  Most cosmic ray antiprotons observed near the Earth are secondaries produced
in collisions of energetic cosmic ray (CR) particles with interstellar gas. The
spectrum of secondary antiprotons is expected to peak at ~2 GeV and decrease
sharply at lower energies. This leaves a low energy window in which to look for
signatures of exotic processes such as evaporation of primordial black holes or
dark matter annihilation. In the inner heliosphere, however, modulation of CRs
by the solar wind makes analysis difficult. Detecting these antiprotons outside
the heliosphere on an interstellar probe removes most of the complications of
modulation. We present a new calculation of the expected secondary antiproton
flux (the background) as well as a preliminary design of a light-weight,
low-power instrument for the interstellar probe to make such measurements.
