1. A method for detecting a target in a non-homogeneous environment using space-time adaptive processing of a radar signal, comprising the steps of: normalizing training data of the non-homogeneous environment to produce normalized training data; representing the normalized training data as a normalized sample covariance matrix; tracking a subspace represented by the normalized sample covariance matrix to produce a clutter subspace matrix; determining a test statistic representing a likelihood of a presence of the target in the radar signal based on the clutter subspace matrix and a steering vector; and comparing the test statistic with a threshold to detect the target, wherein the steps are performed by a processor.