LSST: from Science Drivers to Reference Design and Anticipated Data Products
This is a living document. Click here [PDF] for the latest version (arXiv:0805.2366); version 3.1 of Aug 29, 2014.
Major advances in our understanding of the Universe frequently arise from dramatic improvements in our ability to accurately measure astronomical quantities. Aided by rapid progress in information technology, current sky surveys are changing the way we view and study the Universe. Next-generation surveys will maintain this revolutionary progress. We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain multiple images covering the sky that is visible from Cerro Pachón in Northern Chile. The current baseline design, with an 8.4m (6.7m effective) primary mirror, a 9.6 deg2 field of view, and a 3.2 Gigapixel camera, will allow about 10,000 square degrees of sky to be covered using pairs of 15-second exposures twice per night every three nights on average, with typical 5σ depth for point sources of r ~ 24.5 (AB). The system is designed to yield high image quality as well as superb astrometric and photometric accuracy. The total survey area will include 30,000 deg2 with δ < +34.5°, and will be imaged multiple times in six bands, ugrizy, covering the wavelength range 320—1050 nm. The project is scheduled to begin the regular survey operations before the end of this decade. About 90% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg2 region about 1000 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to r ~ 27.5. These data will result in databases including 10 billion galaxies and a similar number of stars, and will serve the majority of the primary science programs. The remaining 10% of the observing time will be allocated to special projects such as a Very Deep and Fast time domain survey. We illustrate how the LSST science drivers led to these choices of system parameters, and describe the expected data products and their characteristics. The goal is to make LSST data products available to the public and scientists around the world — everyone will be able to view and study a high-definition color movie of the deep Universe.