  An analogue of the Newton-Wigner position operator is defined for a massive
neutral scalar field in de Sitter space. The one-particle subspace of the
theory, consisting of positive-energy solutions of the Klein-Gordon equation
selected by the Hadamard condition, is identified with an irreducible
representation of de Sitter group. Postulates of localizability analogous to
those written by Wightman for fields in Minkowski space are formulated on it,
and a unique solution is shown to exist. A simple expression for the
time-evolution of the operator is presented.
