  Evaluation of nucleon decay modes and branching ratios in a non-minimal
supersymmetric SO(10) grand unified theory is presented. The non-minimal GUT
considered is the supersymmetrised version of the `realistic' SO(10) model
originally proposed by Harvey, Reiss, and Ramond, which is realistic in that it
gives acceptable charged fermion and neutrino masses within the context of a
phenomenological fit to the low energy standard model inputs. Despite a
complicated Higgs sector, the SO(10) $\underline{10}$ Higgs superfield mass
insertion is found to be the sole contribution to the tree level F-term
governing nucleon decay. The resulting dimension 5 operators that mediate
nucleon decay give branching ratio predictions parameterised by a single
parameter, the ratio of the Yukawa couplings of the $\underline{10}$ to the
fermion generations. For parameter values corresponding to a lack of dominance
of the third family self coupling, the dominant nucleon decay modes are $p
\rightarrow K^{+} + \bar{\nu}_{\mu}$ and $n \rightarrow K^{0} +
\bar{\nu}_{\mu}$, as expected. Further, the charged muon decay modes are
enhanced by two orders of magnitude over the standard minimal SUSY SU(5)
predictions, thus predicting a distinct spectrum of `visible' modes. These
charged muon decay modes, along with $p \rightarrow \pi^{+} + \bar{\nu}_{\mu}$
and $n \rightarrow \pi^{0} + \bar{\nu}_{\mu}$, which are moderately enhanced
over the SUSY SU(5) prediction, suggest a distinguishing fingerprint of this
particular GUT model, and if nucleon decay is observed at Super-KAMIOKANDE the
predicted branching ratio spectrum can be used to determine the validity of
this `realistic' SO(10) SUSY GUT model.
