HUBBLE-SPACE-TELESCOPE IMAGE-RESTORATION IN ITS 4TH YEAR

The NASA/ESA Hubble Space Telescope (HST), an astronomical observatory launched in 1990 into a low-altitude space orbit, was designed to deliver near-diffraction limited images, but its optics suffered from substantial spherical aberration. The HST image restoration problem is aggravated by insufficient image sampling, by a mixture of noise sources including spatially non-stationary, non-Gaussian noise, and by the desire to quantitatively evaluate the restored data. Restoration efforts have helped to minimize the impact of the data distortions on HST's scientific return. At the end of 1993 HST was refurbished, and its optics have largely been restored to meet the design goals. Nevertheless, image restoration remains important to treat problems such as combining dithered, undersampled image frames, or to combine images with different resolutions and signal-to-noise ratios.