Nonsparsity influence on the ISAR recovery from reduced data [Correspondence]

The analysis of inverse synthetic aperture radar (ISAR) image recovery from a reduced set of data presented previously (IEEE Transactions on Aerospace and Electronic Systems, 51, 3 [Jul. 2015], 2093-2106) is extended in this correspondence to an important topic of signal nonsparsity (approximative sparsity). In real cases the ISAR images are noisy and only approximately sparse. Formula for the mean square error in the nonsparse ISAR, reconstructed under the sparsity assumption, is derived. The results are tested on examples and compared with statistical data.