All MAST catalog holdings are available via a ConeSearch endpoint. The Sloan Digital Sky Survey (SDSS) Data Release 12 (SDSS DR12) contains all SDSS observations through July 2014. The STScI mirror is available here. More information on SDSS and this data release are available at http://www.sdss.org/dr12/. All available missions are listed at http://archive.stsci.edu/vo/mast_services.html.