VERSION

${DESI_ROOT}/survey/catalogs/{RELEASE}/mocks/AbacusSummit/{OBSCON}/{VERSION} host 25 Abacus LSS catalogs (and associated randoms) separated by OBSCON: DARK or BRIGHT and followed by internal version, where for DARK (LRG, ELG and QSO) is v4.2 and for BRIGHT (BGS) is v1.

From the landing page, you will find the initial catalog in the Y1 footprint (called forFA files), the lrg_mask file (used only to mask LRGs, present only on the DARK obscon) and 2 directories called altmtl{MOCKREA} and mock{MOCKREA} where {MOCKREA} is the mock realization from [0,25).

Here you can find 3 distinct mock flavours depending on the level of realism:

• Complete: no fiber assigment effects, just the tracers that are reachable by any DESI fiber (found under mock{MOCKREA})

• FFA: from Fast Fiber Assigment. It estimates fiber assigment probabilistically learning from the data, based on number of passes and local density (found under mock{MOCKREA})

• altmtl: Estimated using the same fba algorithm, passes and hardware configuration as the data (found under altmtl{MOCKREA}). To replicate the fiber assigment processing, follow the instructions in LSS repo.

Details about the content and production of the LSS catalogs that we follow for the mocks are found in Ross et al. (2025). These mocks were used in the main BAO cosmological analysis, more details in DESI Collaboration (2025).

Details comparing the three mock flavous can be found in Bianchi et al. (2025)

• mock{MOCKREA} : It contains both the FFA and Complete mock flavours, depending on the lñeven of realism
• altmtl{MOCKREA} : It contains the AltMTL mock flavour, with the highest level of realism
• forFA{MOCKREA}.fits : Initial file with tracers from the Abacus CutSky with appropiate columns and selected on the DR1 footprint
• forFA{MOCKREA}_matched_input_full_lrg_imask.fits : Optional, only present for OBSCON = DARK. Used to remove LRGs affected by bright stars