Given an observable pair of matrices (C;A) we consider the manifold
of (C;A)-invariant and observable subspaces having a fixed Brunovsky-
Kronecker structure. Using Arnold’s techniques we obtain the explicit
form of a miniversal deformation of a marked and observable (C;A)-
invariant subspace with regard to the usual equivalence relation. As an
application, we obtain the dimension of the orbit and we characterize
the structurally stable subspaces.