Crews use a special machine to install an individual wedge-shaped petal in DESI’s focal plane, which is installed atop the Mayall Telescope at Kitt Peak National Observatory near Tucson, Arizona. The roundish focal plane is made up of 10 petals, and each petal holds 500 robotic positioners that individually target galaxies to collect their light via thin fiber-optic cables. Photo: Christian Soto, National Optical-Infrared Astronomy Research Laboratory/AURA/NSF