The SDSS Surveys

SDSS-I/SDSS-II

• ugriz imaging of northern Spring sky and a few strips of the Fall sky
• Ultra-deep imaging of Fall equatorial strip (Stripe 82)
• Fiber spectroscopy of galaxies with r < 17.77

• Spectroscopic survey of stars in the Milky Way

• Survey to repeatedly scan Fall equatorial strip (Stripe 82) to search for supernovae

DR7

• Final data release of SDSS-II
• Contains data products from all surveys

• Background oversubtraction near large galaxies
• Poor/incomplete photometry at low Galactic latitude (|b|<25) -- mainly an issue for SEGUE fields

SDSS DR7 sky coverage. Grey = Legacy Survey. Red = SEGUE. Blue/Green = auxilary imaging/spectroscopy

SDSS-III

• Designed to map the spatial distribution of Luminous Red Galaxies (LRGs) and quasars to detect imprint of baryon acoustic oscillations imprinted in early universe
• Fills in imaging of northern Fall sky
• Spectra of 1.5 million Luminous Red Galaxies at z=0.3-0.7
• Spectra of 100,000 QSOs between z=2.3-2.8

• Continuation of SEGUE, focusing on stars in the Galactic halo

• NIR spectroscopy of red giant stars in Galactic bulge, bar, disk and halo

• Tracks radial velocities of 11,000 stars to search for gas giant planets

DR8

• Fall imaging from BOSS, yielding contiguous coverage of Fall sky
• Improved pipeline applied to all data (including dr7, but not Stripe 82)
• New SEGUE -2 spectroscopic plates, and some previously unreleased ones (mostly poor quality)
• New matching of spectroscopic and optical sources (no longer matches spectroscopy to closest object, but which object contributes most light)

• Overestimate of sky background (improved since DR7, but not perfect)
• ~1% of fields missing in catalog due to time-out of pipeline (common around large galaxies and crowded fields)

SDSS DR8 sky coverage. Red regions denote SEGUE plates

DR9 -- Coming soon (July 2012)

• First release of BOSS spectra in Fall sky

DR10 (July 2013)

• APOGEE and BOSS spectra

DR12 (December 2014)

• Final release of all data products