to the COSMOS color system in order to select the targets in a consistent way. We used the CANDELS [@Grogin11] photometry in a subset of the COSMOS field together with the CANDELS photometry in SXDS and EGS to derive a rough color conversion between the fields.

Target prioritization for C3R2 is based on two main factors: (1) the usefulness of a galaxy for calibrating the  relation, and (2) the likelihood of obtaining a secure redshift given the instrument, exposure time, and expected galaxy properties. The usefulness of a particular galaxy to the redshift calibration effort depends both on how common its colors are in the data and whether high-confidence redshifts for galaxies with similar colors already exist.

Based on these considerations, we developed a prioritization scheme for galaxies that weights sources in unsampled cells of the SOM more heavily, and also gives preference to more common galaxy colors. The priorities for C3R2 are adaptive as new data is obtained and more of the color space is filled in. For the 2016A run our priority scheme was as follows:

1.  [We assign a initial priority value of 10 to objects occupying cells with no spectroscopic redshifts of even moderate quality (the 