Legacy Survey observations began in August 2014. Each position in the sky will be observed in three "passes" in each of three filters (g, r, z). "Pass 1" is observed in photometric, good-seeing conditions. "Pass 2" and "Pass 3" are observed in progressively worse conditions. This strategy will ensure a photometric solution across the full survey area.
In addition to observations carried out as part of the Legacy Survey, data releases will include reductions of data from other programs in (g, r, z) that overlap the Legacy Survey footprint.
The images below depict the status of the survey in each band as of Data Release 3 (DR3), color-coded by the number of passes. DESI area that is yet to be observed is marked in light gray. The lines track Galactic latitudes of 0, -10 and +10 degrees.