A telescope project from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) will use a planned array of 5,000 galaxy-seeking robots to produce a 3D map of the universe. Dubbed ProtoDESI, the scaled-down, 10-robot system will help scientists achieve the pinpoint accuracy needed to home in on millions of galaxies, quasars, and stars with the Dark Energy Spectroscopic Instrument (DESI).

ProtoDESI will be installed on the Kitt Peak National Observatory's Mayall Telescope this August and September.

The thin, cylindrical robots to be tested in ProtoDESI each carry a fiber-optic cable. The cable will be precisely pointed at selected objects in the night sky in order to capture their light.

Each 10-inch-long robot contains two small motors. Because of the motor's two independent rotating motions, DESI’s robots can point their fiber-optical cables at any sky object within a 12-millimeter-diameter area. In the completed DESI array, the motions will enable the 5,000 robots to cover every point above their metal, elliptical base, which measures about 2.5 feet across.

While DESI’s robots will primarily target galaxies, ProtoDESI will use mostly bright, familiar stars to tune its robotic positioning system and ensure the system is accurately tracking with the motion of objects in the sky. Mounted next to the positioners is a custom digital camera known as the GFA (Guide, Focus, and Alignment) that will remain targeted on a “guide star” — a bright star that aids the tracking of other objects targeted by the robot-pointed fibers.

DESI robots will poke out from 10 wedge-shaped “petals” fitted together in a focal plate assembly. Each petal contains 500 robots. The first petal will be fully assembled by October at Berkeley Lab and tested at the lab through December. The multi-petal design allows engineers to remove and replace individual segments.

The completed project will feature 10 high-resolution spectrographs, which measure the properties of objects’ light. The measurements will reveal how fast faraway galaxies are moving away from us and their distribution, and will help scientists trace the universe’s expansion history back 12 billion years.

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