Site Map

Available Tools for Data Access

This page describes several tools for accessing the SDSS-III data: the Catalog Archive Server (CAS), the Science Archive Server (SAS), and direct data file access via rsync, wget, or http.

Catalog Archive Server (CAS)

Catalog data are available through SkyServer (also known as the Catalog Archive Server, or CAS). SkyServer also offers interactive tools to browse through SDSS images with links to associated spectra and catalog data about the objects on the images.

DR9 SkyServer Interactive query tools for CAS
SkyServer Imaging Query Form Simple image query form interface
SkyServer Spectroscopic Query Form Simple spectroscopic query form interface
SkyServer Cross-ID Match list of RA/Dec or IDs to imaging or spectroscopic catalog
Image List Generate JPGs for a large set of objects
SkyServer Navigate Point-and-click interface to JPG image of SDSS sky
SDSS Command Line Query Tool (sqlcl) Python module for interfacing with CAS at the command line
DR9 CASJobs CAS SQL advanced user interface (use DR9 context)

The advanced CasJobs database interface gives you 500 MB or more of personal database space to select, analyze, and cross-identify SDSS data.

Science Archive Server (SAS)

While CAS is the primary interface to the catalog data, the Science Archive Server (SAS) is the primary interface to the original images and spectra. It provides tools to interactively view and download SDSS spectra, download images of SDSS fields, and generate mosaics of those fields.

In addition, SAS contains directory structures with the data in the original binary (FITS) and text file formats. To understand the directory structure and file formats, please see the imaging data and spectro data pages, as well as the basics of SDSS spectroscopy, SDSS imaging, and the detailed data model.

SAS Spectra Tool to view spectra and retrieve FITS
SAS Images Tool to view images and retrieve FITS
SAS Mosaic Tool to create larger-scale mosaic FITS images
Imaging catalogs Directories of full image catalog files BOSS_PHOTOOBJ data model
Corrected frames Directories of full corrected image frames BOSS_PHOTOOBJ/frames data model
Datasweep catalogs Directories of reduced "sweep" imaging catalog data files PHOTO_SWEEP data model
Spectroscopic catalogs Directories of SDSS spectra and catalogs Spectro catalog documentation and SPECTRO_REDUX data model

Note that both CAS and SAS will give you exactly the same catalog data. Essentially all of the data input into CAS is included in some form in the SAS. However, there are some small changes in naming convention (for example, "resolve_status" in SAS flat files is referred to as "resolveStatus" in CAS).

Direct file downloads

Expert users may need direct access to the data files themselves instead of webpage or database views of it. For this purpose, we provide the ability to directly download the files from SAS as described on the bulk download page.

SDSS Application Programming Interface (API)

The SDSS API provides a programmatic interface to DR9 spectroscopic data — an easy way to query and retrieve spectra from within scripts. The API provides a quick way to retrieve one or many spectra as FITS or JSON files. The SDSS API can provide a foundation to build your own tools or interfaces to SDSS data, without having to worry about downloading or hosting the data yourself. Documentation, details, and examples are available at