The Sloan Digital Sky Survey started routine observing in 2000, and since then has gone through four generations of surveys. The current generation is the Fifth Generation of Sloan Digital Sky Surveys (SDSS-V), and the data of its mapper programs can be found in Data Release 18.
The following is a list of all the spectroscopic survey programs that were completed in SDSS-I,-II,-III and -IV, and includes information on how to access the spectra and other data products of these surveys. No new data of these surveys is released in DR18.
SDSS-IV Surveys (2014 – 2020)
SDSS-IV (2014-2020) extended precision cosmological measurements to a critical early phase of cosmic history (eBOSS), expanded its revolutionary infrared spectroscopic survey of the Galaxy in the northern and southern hemispheres (APOGEE-2), and for the first time, used the Sloan spectrographs to make spatially resolved maps of individual galaxies (MaNGA). Two smaller surveys were executed as subprograms of eBOSS: the Time Domain Spectroscopic Survey (TDSS) was the first large-scale, systematic spectroscopic survey of variable sources; while the SPectroscopic IDentification of EROSITA Sources (SPIDERS) provided a unique census of supermassive black-holes and large scale structure growth, targeting X-ray sources from ROSAT, XMM and eROSITA. The MaNGA stellar library (MaStar) delivered an optical stellar library covering a wide range of stellar parameters.
An overview of these completed SDSS-IV spectroscopic surveys can be found in the SDSS-IV section of our Mappers page. More information on how to access the SDSS-IV spectra and data products, how to work with the data, descriptions of the data formats as well as tutorials and caveats for the different surveys:
SDSS-III Surveys (2008 – 2014)
SDSS-III (2008-2014) undertook a major upgrade of the venerable SDSS spectrographs and added two powerful new instruments to execute an interweaved set of four surveys, mapping the clustering of galaxies and intergalactic gas in the distant universe (BOSS), the dynamics and chemical evolution of the Milky Way (SEGUE-2 and APOGEE), and the population of extra-solar giant planets (MARVELS). You can still visit the old SDSS3 Website, but it is no longer updated.
An overview of these completed SDSS-III spectroscopic surveys can be found here. More information on how to access the SDSS-III spectra and data products, how to work with the data, descriptions of the data formats as well as tutorials and caveats for the different surveys:
SDSS-I/II Surveys (2000 – 2008)
In its first five years of operations, the SDSS carried out deep multi-color imaging over 8000 square degrees and measured spectra of more than 700,000 celestial objects. With an ever-growing collaboration, SDSS-II (2005-2008) completed the original survey goals of imaging half the northern sky and mapping the 3-dimensional clustering of one million galaxies and 100,000 quasars. SDSS-II carried out two additional surveys: the Supernova Survey, which discovered and monitored hundreds of supernovae to measure the expansion history of the universe, and the Sloan Extension for Galactic Understanding and Exploration (SEGUE), which extended SDSS imaging towards the plane of the Galaxy and mapped the motions and composition of more than a quarter million Milky Way stars. The classic SDSS Website is still available, but it is no longer updated.
An overview of these completed SDSS-I/II surveys can be found here. More information on how to access the SDSS-I/II imaging, spectra and data products, how to work with the data, descriptions of the data formats as well as tutorials and caveats for the different surveys: