To produce stunning images of our galaxy like this, your rinky-dink smartphone camera just isn’t going to cut it. No, to generate 9GP masterpieces, you’ll need to use the world’s largest infrared survey telescope outfitted with the world’s largest infrared camera.
Located 2,518 meters above sea level at the ESO’s Paranal Observatory in Chile, the Visible and Infrared Survey Telescope for Astronomy (VISTA) is charged with performing an unprescedented systemic survey of the Southern Sky, specifically in the near-infrared range. The VISTA actually sits the next peak over from the ESO Very Large Telescope (VLT), which surveys the visible spectrum of light over the same sky.
The VISTA relies on a pair of mirrors to reflect incoming light into its massive infrared camera. The primary mirror sports a 4.1 meter diameter and is cast from Zerodur, a proprietary lithium aluminosilicate glass-ceramic formula — just polishing it took nearly two years. It is the most highly curved mirror ever made at this size, coated in silver (which reflects 98 per cent of near infrared light) rather than the standard aluminium, and deviates from perfection by less than three nanometres — 1/3000th the width of a human hair. A series of computer-guided actuators help position this massive piece of glass and direct light into the secondary, 1.24 meter convex hyperboloid mirror. It too is controlled by a series of actuators that adjust its position, tip, and tilt.
The VISTA’s infrared camera, built by teams from the Rutherford Appleton Laboratory, the UK Astronomy Technology Centre, and Durham University, is similarly gargantuan. Weighing in at nearly three tons, the VISTA camera is by far the world’s largest. It’s 16 internal IR-sensors combine to produce a staggering 67 million pixel, 2048×2048 resolution image of longer-than-visible wavelengths. Since the IR sensors are designed as sensitively as possible to pick up the faintest of Brown Dwarf, the entire camera system has to be chilled to -200C. The largest infrared-transparent window ever made provides a clear line-of-sight to the outside world.
The individual sensors on the focal plate are separated slightly from each other — 90 per cent their width, 50 per cent their length — in order to cover larger swaths of the night sky. Problem is, doing so results in “pawprints” like the image to the left. To counteract this, the VISTA actually takes a series of six images for each survey section.
VISTA has been built exclusively for documenting the southern sky and will do so via six massive surveys over the next five years, generating 200-300 GB per night. This data is expected to give researchers a fresh look at many items throughout the universe that are otherwise too faint to observe — faint brown dwarves, distant stars obscured by gas or dust clouds, even perhaps the nature of dark matter and energy. The ESO even expects to generate a 3D map of the observable Universe (or at least about the five most-interesting per cent of it). [ESO – VISTA – Wikipedia 1, 2 – Image: ESO]