Weak lensing cosmology experiments of the 2020s will require accurate redshift estimates for billions of faint galaxies. The Complete Calibration of the Color-Redshift Relation (C3R2) Survey aims to fill out the galaxy color space with spectroscopic redshifts to the depth of the planned ESA/NASA Euclid mission (i~24.5), thus providing a firm foundation for estimating accurate redshift distributions based on broadband imaging in the optical through near-infrared.
The C3R2 survey has been awarded 50.5 nights on Keck as well as 200h of VLT time (KMOS and FORS). Keck contributions have come from all Keck partners: NASA (20 nights, between D. Stern and D. Masters), Caltech (16 nights, PI J. Cohen), U. of Hawaii (PI D. Sanders, 6 nights) and University of California (PI B. Mobasher, 2.5 nights). Over 5000 new spectroscopic redshifts have been obtained by the survey. Reduced spectra are made public through the Keck Observatory Archive (KOA).