Jun 14, 2016 @ 18:41 |
Berkeley Lab is building and testing a robotic array for a telescope project that will produce a 3-D map of the universe including millions of galaxies. Ten robots will be tested in a prototype called ProtoDESI, and the full project, called DESI (Dark Energy Spectroscopic Instrument), will feature 5,000 robots.
The full DESI project, which is managed by Berkeley Lab, involves about 200 scientists and about 45 institutions from around the globe. DESI will provide the most detailed 3-D map of the universe and probe the secrets of dark energy, which is accelerating the universe’s expansion. It is also expected to improve our understanding of dark matter, the infant universe, and the structure of our own galaxy.
The thin, cylindrical robots that will be tested in ProtoDESI each carry a fiber-optic cable that will be precisely pointed at selected objects in the night sky in order to capture their light. A predecessor galaxy-measuring project, called BOSS, required the light-gathering cables to be routinely plugged by hand into metal plates with holes drilled to match the position of pre-selected sky objects. DESI will automate and greatly speed up this process.
Each 10-inch-long robot has two small motors in it that allow two independent rotating motions to position a fiber anywhere within a circular area 12 millimeters in diameter. In the completed DESI array, these motions will enable the 5,000 robots to cover every point above their metal, elliptical base, which measures about 2.5 feet across.
That requires precise, software-controlled choreography so that the tightly packed robots don’t literally bump heads as they spin into new positions several times each hour to collect light from different sets of pre-selected sky objects.
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“The main goal of ProtoDESI is to be able to fix fibers on actual objects and hold them there,” said Parker Fagrelius, who is managing the ProtoDESI project at Berkeley Lab. Fagrelius is a UC Berkeley graduate student who is also an affiliate in the Physics Division at Berkeley Lab. ProtoDESI’s robots, assembled at University of Michigan and then shipped to Berkeley Lab, are positioned far enough apart that they won’t accidentally collide during their initial test run.
In addition to the 10-robot system, ProtoDESI is equipped with a set of 16 light-emitting rods—shaped similarly to the robots—that project small points of blue light onto a camera to calibrate the positioning system. The completed project will include 120 of these devices, called “illuminated fiducials.”
The full robotic array planned for DESI will be segmented in 10 pie-wedge-shaped “petals” that each 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 will allow engineers to remove and replace individual petals.
Each robot will have an electronic circuit board and wiring, and on the final DESI project each robot’s fiber-optic cable will be spliced to a 42-meter-long fiber-optic cable that will run to a light-measuring device known as a spectrograph (ProtoDESI will not have a spectrograph).
This video shows the rotating motions of a robotic fiber-optic positioner. ProtoDESI will test a group of 10 robotic positioners, and DESI will feature 5,000 robots. (Credit: Berkeley Lab)
A simulation of the movements of 499 DESI robots, carefully choreographed to avoid bumping into one another, as seen from above. ProtoDESI is testing 10 robots for the completed DESI project, which will have 5,000 robots. (Credit: Joe Silber/Berkeley Lab)
DESI is supported by the U.S. Department of Energy Office of Science; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract to the National Optical Astronomy Observatory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the National Council of Science and Technology of Mexico, and DESI member institutions. The DESI scientists are honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation.
Source: Berkeley Lab