and initial results, including the 1283 high confidence redshifts obtained in the 2016A semester and released as Data Release 1.'
author:
- |
    Daniel C. Masters, Daniel K. Stern, Judith G. Cohen, Peter L. Capak,\
    Jason D. Rhodes, Francisco J. Castander, Stéphane Paltani
bibliography:
- 'biblio.bib'
title: |
    The Complete Calibration of the Color-Redshift Relation (C3R2) Survey:\
    Survey Overview and Data Release 1
---

Introduction
============

The upcoming large-scale cosmology experiments *Euclid* [@Laureijs11], LSST [@Ivezic08] and *WFIRST* [@Spergel15] will depend on robust photometric redshift (photo-z) estimates for billions of faint galaxies in order to obtain a three-dimensional picture of the growth of cosmic structure. Small ($\gtrsim$0.2%) redshift biases can easily dominate the overall error budget in the cosmological parameters measured by these surveys (e.g., [@Huterer06]). Spectroscopic calibration efforts for these missions must therefore measure the color-redshift relation of galaxies with sufficient fidelity to reconstruct the redshift distributions of shear samples with negligible systematic bias. While photometric redshift estimation techniques have grown in sophistication and precision over the past few decades (e.g., [@Benitez00; @Brammer08; @Ilbert09; @Carrasco13; @Speagle16]), existing methods have not met the photo-z accuracy requirements set by weak lensing cosmology.

The relation of seven or eight galaxy broadband colors (referred 