What is the SDSS?

Project Goals

The Sloan Digital Sky Survey (SDSS) is described in the "Blue Book", which is a proposal submitted to NSF. Some details of the project have changed since this proposal, but it is still essentially correct. An updated version of this proposal is being prepared during the Fall of 1993. So far, there are two review articles:

"The Sloan Digital Sky Survey", J. E. Gunn and G. R. Knapp, from a lecture presented at the symposium "Astronomical Surveys" in honor of Gerry Neugebauer's 60th birthday. Published in Sky Surveys, Protostars to Protogalaxies, editor T. Soifer, Ast. Soc. of Pacific conference series, #43, p. 267 (1992).
"A Wide-Field Telescope for High-Latitude Surveys - CCD Multiband Photometry and Multifiber Spectroscopy," R.G. Kron, 1992, in Progress in Telescope and Instrumentation Technologies, ESO Conference and Workshop Proceedings No. 42, ed. M.-H. Ulrich (Garching:ESO), p. 635.

The document "Principles of Operation" (POO) defines the project as follows:

"The goal of the project is to build and operate a dedicated telescope suitable for wide-angle surveys of the sky which will address critical issues in extragalactic astronomy, especially in the field of large-scale structure." (POO IA)

The priorites are defined in the POO as follows:

Core Projects

(1) In the pi steradians of the available North Galactic Pole (b > 30 degrees), we shall conduct surveys in the following manner:
- Obtain a photometric survey, in four or five filters to 23rd magnitude (R), 5 sigma, for stellar objects;
- obtain redshifts for all galaxies down to 19th magnitude (B);
- obtain redshifts for all QSOs down to 20th magnitude (B).
The photon-limited velocity precision at the survey limit should be better than 60 km/sec. The data should be archived as a full data set of all pixels on the sky (10 terabytes), as well as in reduced data sets, for later analysis. Such reduced sets include rasters of all galaxies brighter than some limit, image parameters for all galaxies to the imaging survey limit, and catalogs of the positions, redshifts, and properties of observed quasars.
(2) In the available South Galactic Pole region there will be a deeper survey in a strip 2 degrees (dec) by 50 degrees, in order to:
- obtain a photometric survey, in four or five filters to 25th magnitude (R), 5 sigma, for stellar objects;
- obtain redshifts for all galaxies down to 20th magnitude (B);
- obtain redshifts for all QSOs down to 21st magnitude (B).
(3) In the additional available sky covering the Galactic disk, a deep photometric survey will be conducted on a best effort basis to 23rd magnitude (R), 5 sigma.

Prioritization of resources -- financial, human, and telescope availability -- is indicated by the ordering (1), (2), (3) above. The jointly raised funds will be dedicated to these projects. Completion of project (3) may require additional time and funding.