“…Restricting our attention to the singular structure-specifically, to a certain set in phase space called the wavefront set-allows us to use the tools of microlocal analysis. [8][9][10][11] This strategy was first applied to imaging problems by Beylkin 12 ; its uses in seismic prospecting, [13][14][15][16] X-ray tomography, 17,18 sonar, 19 and synthetic-aperture radar 20,21 are active areas of research. An approach similar to the one we pursue here, in which we use microlocal analysis not to do imaging but instead to study the connection between features of the target and the data, was considered for the X-ray tomography problem by Quinto.…”