“…We shall -N approximate solutions q of this problem by a sequence {qN} of solutions to q estimation problems that are computationally more tractable than our original problem. The approach taken here is similar in spirit to that of a number of other related efforts (see [1], [4], [5], [6], [7], [9], [13] and [16]) in that the original estimation problem is reformulated in a Hilbert space setting where Ritz-Galerkin type ideas may be applied to construct the approximate problems. To this end, we rewrite (2.1)-(2.3) as an abstract evolution equation (AEE) in an infinite-dimensional state space; although the use of spaces and operators here is quite standard and well-established in the literature, the dependence of our problem on unknown parameters requires that we make an effort to carefully define the operators involved.…”