A finite number of point observations which determine a non-autonomous fluid flow

We show that a finite number of point observations serve to determine the f low field throughout the entire domain for certain two-dimensional (2D) flo ws. In particular, we consider the 2D Navier-Stokes equations with periodic boundary conditions and a time-dependent forcing which is analytic in spac e. Using the theory of non-autonomous attractors developed by Chepyzhov and Vishik, and the theory of point observations developed by Friz and Robinso n, we show that almost every choice of a sufficient number of 'nodes' in th e domain gives an evaluation map u vertical bar --> (u(x(1)),..., u(x(k))) which is one-to-one between the attractor and its image.