  In this paper we study microlocal singularities of solutions to Schrodinger
equations on scattering manifolds, i.e., noncompact Riemannian manifolds with
asymptotically conic ends. We characterize the wave front set of the solutions
in terms of the initial condition and the classical scattering maps under the
nontrapping condition. Our result is closely related to a recent work by
Hassell and Wunsch, though our model is more general and the method, which
relies heavily on scattering theoretical ideas, is simple and quite different.
In particular, we use Egorov-type argument in the standard pseudodifferential
symbol classes, and avoid using Legendre distributions. In the proof, we employ
a microlocal smoothing property in terms of the radially homogenous wave front
set, which is more precise than the preceding results.
