The VISTA camera
At the heart of VISTA is a 3-tonne camera containing 16 special detectors sensitive to infrared light, with a combined total of 67 million pixels. Observing at wavelengths longer than those visible with the human eye allows VISTA to study objects that are otherwise impossible to see in visible light because they are either too cool, obscured by dust clouds or because they are so far away that their light has been stretched beyond the visible range by the expansion of the Universe. To avoid swamping the faint infrared radiation coming from space, the camera has to be cooled to -200 degrees Celsius and is sealed with the largest infrared-transparent window ever made. The VISTA camera was designed and built by a consortium including the Rutherford Appleton Laboratory, the UK ATC and the University of Durham in the United Kingdom.
The 16 chips in the VISTA camera are quite widely spaced, so the telescope takes multiple images at different pointings to fill in the gaps. The VISTA field of view is compared with that of other infrared cameras, on the ground (ISAAC and HAWK-I on the VLT, WFCAM on UKIRT), and in space (NICMOS on Hubble) as well as the size of the Moon, in the picture below. The new WFC3 camera on the NASA/ESA Hubble Space Telescope is not shown. It has a field slightly smaller than ISAAC on ESO’s VLT.