A: VISTA is the largest telescope in the world dedicated to surveying the sky at near-infrared wavelengths. Its primary mirror is 4.1 metres in diameter and is the most highly curved of its size. The extremely high curvature reduces the focal length, and significantly widens the field of view, enabling VISTA to map large areas of the sky. At the same time, the large collecting surface allows VISTA to detect faint objects, seeing deep into space. Manufacturing a single mirror with these dimensions and characteristics is a formidable accomplishment.
A: By mapping large areas of the sky, the survey telescopes create vast archives of images and catalogues of objects, also providing interesting targets to be studied in more detail by the VLT itself. With their respective 67- and 268-megapixel cameras, VISTA and the VST will produce far more data every night than all the other instruments on the VLT combined.