Astronomical Speckle Imaging

Speckle imaging is a technique for recovering diffraction limited images from sequences of atmosphere-degraded, short exposure photographs obtained at a large telescope. The technique is derived from speckle interferometry and shares many of the characteristics of that process, including dependence of the output signal-to-noise on number of frames processed and relative insensitivity to fixed telescope aberrations and noise in the image record. Speckle interferometry has been demonstrated to yield telescope-diffraction-limited information, but only in the form of spatial power spectra. Speckle imaging averages a different quantity, the statistical autocorrelation of the image Fourier transform, which contains all the information in the averaged power spectra plus the transform phase information required to recover an image. Two-dimensional digital simulations of the process for extended continuous-tone objects are presented, and include the case where severe static telescope aberrations are present.