Observatories in Chile and Mexico are vying to host a new kind of astronomical facility, which, if approved, will set the standard for sensitive all-sky surveys in the next decade.

The Large Synoptic Survey Telescope (LSST) corporation, based in Tucson, Arizona, has asked for proposals from astronomers at three sites chosen for their excellent visibility: Las Campanas and Cerro Pachón in Chile, and San Pedro Mártir in Mexico. The winning site will be announced in April.

Mexico's San Pedro Mártir site is favoured for its remoteness. Credit: CORBIS/ROBERT HOLMES

The LSST's ambitious goal is a kind of “celestial cinematograph”, says project director Tony Tyson of the University of California, Davis. A single 8.4-metre telescope will photograph the entire sky every three days, across a range of wavelengths from ultraviolet to near-infrared.

The survey will pick up far fainter objects than today's Sloan Digital Sky Survey, and LSST images could be used for a range of astronomical problems, from searching for dark matter to tracking fast-moving asteroids. The volume of data generated will be unprecedented — 20 terabytes of raw image data, more than the entire Sloan Survey's output, every night.

Tyson sees the LSST as a “totally different paradigm” for astronomy, akin to the Human Genome Project. All the data will be shared freely, as will the algorithms for image processing. He says the project is now spending most of its time on software development, and recently used Wayne Rosing, Google's former senior vice-president of engineering, as a consultant.

Private funding has allowed work to begin on the mirrors, and the National Science Foundation (NSF) is providing US$14.2 million over four years. Still, that's far from the $270 million needed for construction and a decade of operations. Tyson hopes the US Department of Energy and the NSF will contribute roughly $100 million each, with the rest coming from private sources.

The Chilean sites already have several premier telescopes, including the Gemini and SOAR (Southern Astrophysical Research Telescope) on Cerro Pachón and the Magellan telescopes on Las Campanas. The San Pedro Mártir site in the Mexican state of Baja California is less well known; its largest instrument is a modest 2.1 metres in diameter.

But the remoteness of the Mexican site could be a bonus; the Chilean observatories have had to contend with light pollution as the population builds up in nearby communities. The ‘astro-climate’ for the three sites — which includes factors from atmospheric transparency and stability to the number of clear nights per year — is virtually identical, says Tyson. So other considerations, from local infrastructure to politics, may sway the decision.