desitarget selects targets for spectroscopic follow-up by Dark Energy Spectroscopic Instrument (DESI). The pipeline uses bitmasks to record that a specific source has been selected by a particular targeting algorithm, setting bit-values in output data files in a number of different columns that indicate whether a particular target meets specific selection criteria. desitarget also outputs a unique TARGETID that allows each target to be tracked throughout the DESI survey. This TARGETID encodes information about each DESI target, such as the catalog the target was selected from, whether a target is a sky location or part of a random catalog, and whether a target is part of a secondary program.

The Feed Forward Neural Network SYSNet models the relationship between the imaging maps, such as stellar density and the observed galaxy density field, in order to mitigate the systematic effects and to make a robust galaxy clustering measurements. The cost function is Mean Squared Error and a L2 regularization term, and the optimization algorithm is Adaptive Moment (ADAM).

"legacypipe" is the code used to produce the DESI Legacy Imaging Surveys (aka the Legacy Surveys). It can processes individual exposures from many cameras, including the Dark Energy Camera on the Blanco telescope, the 90Prime camera on the Bok telescope, the Mosaic3 camera on the Mayall telescope (these three were used for the Legacy Surveys); as well as the Hyper-SuprimeCam on Subaru, the old SuprimeCam on Subaru, MegaCam on the Canada-France-Hawaii Telescope, and image products from the GALEX and WISE satellites. Legacypipe performs source detection, and then measurement via forward-modeling using the Tractor code. It generates coadded output images as well as catalogs, plus a variety of metrics useful for understanding the properties of the imaging.