I spy with my little fibre, ten million or so galaxies

Astronomers welcome their new robot overlords

The robotic proto-DESI
LBL's ProtoDESI: aiming fibres at the sky. Image: Paul Mueller/Berkeley Lab

Lawrence Berkeley National Laboratory boffins are getting ready to point thousands of optical fibres at the night sky, starting with a 10-robot system proof-of-concept.

The ProtoDESI the boffins are wiring up will use robots to aim optical fibres at distant galaxies, a light-gathering trick the DESI (Dark Energy Spectroscopic Instrument) project wants to use to precisely capture their position.

The project has already run up a manual demonstration of fibre-based telescopes, but DESI's aim is to capture tens of millions of galaxies, so aiming the fibres has to be automated.

That's where ProtoDESI comes in, as a demonstrator now under construction at the lab prior to installation at the Mayall Telescope in Arizona in August-September.

Even with just ten robots, swinging the fibre optic heads under computer control on two axes to aim them is difficult without a slip-up like a collision. Rather than build the whole 5,000-robot kit and wreck it with a software bug, the prototype tests the choreography.

DESI is due to run in 2018, capturing optical spectra for its targets to construct a 3D map of the universe out to 10 billion light years.

The hope is that the measurements will help astro-boffins understand the action of the universe-expansion-accelerating dark energy.

Since the purpose of ProtoDESI is to confirm the operation of the system, it's going to be pointing the fibres mostly at bright, familiar stars. A guide, focus and alignment (GFA) digital camera will confirm that the tracking system is pointing the instrument at the right stars.

Berkeley Lab notes that DESI's fibres are going to go through around 200,000 movements when the full experiment runs – which is a lot of bending for the 107-micron core optical fibres it will use. ®

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