Ground-Based High Resolution Imaging in the Visible: The Cambridge Lucky Aperture Synthesis Instrument

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The Hubble Space Telescope has produced astonishing pictures for many years but it will only survive for a few more years at most. Already astronomers are striving to achieve high resolution on the ground but the methods being used such as adaptive optics and laser guide stars are still a long way from being able to deliver good image quality in the visible. The Cambridge Lucky Aperture Synthesis Instrument (CLASI) uses a combination of proven technologies to deliver the highest resolution images that the telescope would be capable of producing if it was above the atmosphere. Usually fluctuations in the atmosphere substantially degrade ground-based images. In this instrument we break up the aperture of the telescope into many sub apertures and then recombine them in a carefully controlled way that lets us check the quality of the images tens of times per second. By selecting those images which are truly of the best quality we can synthesise a telescope in the computer that gives the highest quality image possible using methods already widely used by radio astronomers. This instrument is designed to give a resolution three times better than that of the Hubble Space Telescope, on the ground and a moderate cost. There are still many things that a space telescope will be able to do better than one on the ground but until new space projects are started this is likely to be the only way we can observe the most distant parts of the universe efficiently and with the best image quality.