NOAO 4-m Telescopes for Future Surveys
  The NOAO currently operates the two most capable platforms in the world for optical surveys, the 4-m KPNO (Mayall) and 4-m CTIO (Blanco) telescopes. It was only discovered recently (in 2009) that a field of view of 3 deg diameter is possible on these telescopes. In combination, these two telescopes provide the unique capability of a common telescope platform for full-sky surveys. The survey power (in \'etendue) is 45% that of LSST.   Two ambitious surveys are already planned using these telescopes in the coming decade: Dark Energy Survey (imaging on the Blanco) and BigBOSS (spectroscopy on the Mayall). The BigBOSS collaboration has proposed a survey of 20 million galaxies in one hemisphere, and the full sky could be completed by moving the instrument to its sister platform in the South. These and other possible surveys argue for the continued investment in these uniquely- capable facilities by NSF Astronomy. 
David Schlegel, Michael Sholl
astro-ph.IM