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          | Contents |  
          | We analyze the performance of a data-assimilation method based on a
  linear feedback control when used with observational data that
  contains measurement errors.  Our model problem consists of dynamics
  governed by the two-dimension incompressible Navier--Stokes
  equations, observational measurements given by finite volume
  elements or nodal points of the velocity field and measurement
  errors which are represented by stochastic noise.  Under these
  assumptions, the data-assimilation algorithm consists of a system of
  stochastically forced Navier--Stokes equations.  The main result of
  this paper gives conditions on the observation density which
  guarantee that the expected value of the approximating solution will
  converge to the actual solution to within a factor related to the
  variance of the noise in the measurements. |  |