Survey Design
The LSST will be a large, wide-field ground based telescope designed to obtain sequential images covering the entire visible sky from Cerro Pachon in Northern Chile. The current baseline design, with an 8.4m (6.5m effective) primary mirror and a 9.6 sq.deg. field of view, will allow about 15,000 square degrees of sky to be covered in two photometric bands every four nights (assuming two 15-second exposures per field). The system is designed to yield high image quality as well as superb astrometric and photometric accuracy. The survey area will include 30,000 sq.deg. with Dec<+34.5, and will be imaged multiple times in six bands covering the wavelength range 320--1050 nm.
The vast majority (about 90%) of the observing time will be devoted to a deep-wide-fast survey mode which will observe a 20,000 sq.deg. region in the ugrizy bands about 1000 times (including all bands) during the 10-year survey. The deep-wide-fast survey data will serve the majority of science programs. The remaining 10% of observing time will be allocated to special programs such as Very Deep and Very Fast time domain surveys. We illustrate how LSST science drivers led to these choices of system design parameters.
LSST Science Drivers
Major advances in our understanding of the universe have always come from dramatic improvements in our ability to "see". In the past decade, the large-scale sky surveys have become increasingly appreciated. As a sensitive, multicolor survey over most of the sky, LSST will dramatically impact nearly all fields of astronomy and many new areas of fundamental physics. The essence of LSST is to go deep, wide, and fast, and this strategy will enable an extremely broad range of scientific investigations.
The main science themes that LSST will address, and that are used to optimize the system design, are:
Constraining Dark Energy and Dark Matter
using a variety of probes and techniques whose synergy will fundamentally test our cosmological assumptions and gravity theories; LSST will provide a sample of 3 billion galaxies with excellent photometry and shape measurements, over 100,000 clusters of galaxies, and a sample of several million Type Ia SNe.
Taking an Inventory of the Solar System
and extending the boundaries of our reach in distance and detectable size of potentially hazardous asteroids; LSST will detect and characterize over 80% of 140m or larger killer asteroids, several million main-belt asteroids, and over 100,000 trans-Neptunian objects (e.g. Sedna-like objects will be detectable to beyond 200 AU).
Exploring the Transient Optical Sky
by characterizing known classes of object and discovering new ones; LSST will sample a variety of time scales ranging from 10 sec, to the whole sky every 3 nights, with 1000 visits distributed over 10 years.
Mapping the Milky Way
all the way to its edge with high-fidelity; main-sequence stars will be detected to 100 kpc, RR Lyrae to 400 kpc, and geometric parallaxes will be measured for all stars within 300 pc.
Baseline Specifications
Source: American Astronomical Society 213th Meeting, Poster Exhibit, "LSST: from science drivers to reference design and anticipated data products", Z. Ivezic et al., 460.03