  We extended the notion of Newton-Wigner localization, already constructed in
the bi-dimensional de Sitter space, to the tri-dimensional case for both
principal and complementary series. We identify the one-particle subspace,
generated by the positive-energy modes solution of the Klein-Gordon equation,
as an irreducible representation of the de Sitter group. The time-evolution of
the Newton-Wigner operator was obtained explicitly, and for the complementary
series the evolution is trivial, i.e., there are no dynamics. Also, we
discussed heuristically the existing sign ambiguity when we do not require as a
postulate that the Newton-Wigner functions must be proportional to their
respective solutions in the representation of solutions of the Klein-Gordon
equation.
