The Role of DESI in Photo-z Inference for LSST, Euclid, and Future Cosmological Surveys

We present the results of the DESI Complete Calibration of the Color-Redshift Relation (DC3R2) secondary target survey. The spectroscopic galaxies observed during DESI Science Verification, augmented by DC3R2, that overlap with KiDS-VIKING ugriZYHJKs photometry calibrate the color-redshift relationship and inform photometric redshift (photo-z) inference methods in future weak lensing surveys. With Emission Line Galaxies (ELGs) and Luminous Red Galaxies (LRGs) that provide a complementary color sample, we conservatively span 50% of the color space visible to Euclid and LSST. Examination of the redshift dependence on magnitude at fixed colors will provide a constraint on the use of preferentially bright spectra to calibrate redshifts in a correspondingly fainter photometric sample, which is deeply relevant to the next decade of anticipated, unprecedented survey depth. The effects of spectroscopic completeness and quality are explored, as well as systematic uncertainties introduced with the use of common Self Organizing Maps trained on different photometry than the analysis sample.