4MOST - 4-metre Multi-Object Spectroscopic Telescope
4-m Multi-Object Spectroscopic Telescope
4MOST

First LRS spectra

The first 4MOST Low-Resolution Spectrograph (LRS-A) has now reached “first light” (or first spectra) in the CRAL integration hall in Lyon, France. These first exposures were taken through the blue channel. The most important parameters – image quality, wavelength range and spectral resolution – are all very close to those necessary to meet our goal of doing world class astrophysical research. The LRS opto-mechanical design preforms well, giving us confidence that similar performance will be achieved when assembling the green and red channels of LRS-A, and the second LRS.

Florence Laurent, the head of engineering at CRAL: “I am happy to say that the first arm of LRS-A has been integrated and aligned and we succeeded in making the first exposures. Most importantly, the blue channel already performs close to its scientific and technical specifications. I would like to express my sincerest thanks to the team, Karen Disseau, Jean-Emmanuel Migniau, Didier Boudon, Diane Chapuis, Eric Daguisé, Aurélien Jarno, Arlette Pécontal, Johan Richard, and Alban Remillieux, all of whom overcame many challenges to reach this milestone.”

Matthew Lehnert, the director of CRAL, added: “It’s wonderful to see these results and imagine the exciting scientific results and breakthroughs we will be capable of making with this extremely capable instrument. Without the hard work of the dedicated team at CRAL, imagining these goals would not even be possible. Thank you to everyone for their hard work!”

The blue arm of the LRS-A bench which enabled the first LRS “lab light”.

Exposure of a continuum lamp showing the spectrum across the blue detector (370 – 554 nm). Only six groups of fibres across the slit are illuminated for these tests.

Zoom-in on a few spectral lines of a Mercury lamp, demonstrating the overall image quality of the blue channel. With further work on the alignment and other optimizations, we are confident of being able to reach even better performance.

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