1. A signal parameter estimation system for multiple signal sources comprising: a plurality of actual sensors comprising a partial array receiving signals from the multiple sources, each sensor providing as an output a measurement; a virtual cross-correlation computer receiving the measurements from the actual sensors and including means for calculating the cumulants of the actual sensor signals and means for calculating the cumulants of virtual sinsors characterized as summations of displacement vectors between pairs of actual sensors within the plurality, the virtual sensors comprising a second partial array and means for outputting a covariance matrix comprising the cumulant values corresponding to each cross-correlation of a full array comprising the partial array of actual sensors and the second partial array of virtual sensors; and a subspace parameter estimation system receiving the covariance matrix of the full array and calculating direction of arrival estimates.