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4MOST, the 4m Multi Object Spectroscopic Telescope, is an upcoming optical, fibre-fed, MOS facility for the VISTA telescope at ESO's Paranal Observatory in Chile. Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. The 4MOST consortium consists of several institutes in Europe and Australia under leadership of the Leibniz-Institut für Astrophysik Potsdam (AIP). 4MOST is currently in its Assembly, Integration and Tests Phase with an expected start of science operations in 2023. The design of 4MOST features 2436 fibres split into two low-resolution spectrographs (1624 fibres, three arms, 370-950 nm, R < 4000) and one high-resolution spectrograph (812 fibres, three arms, ~44-69 nm coverage each, R < 18000). The fibre positioner covers a hexagonal field of view of ~4.1 deg². The fibers are 85μm core with an output beam at f/3. CRAL has the full responsibility of the two Low Resolution Spectrographs (LRS). Each LRS is composed of a 200mm beam for an off-axis collimator associated to its Schmidt corrector, three “color” arms hosting f/1.73 cameras with standard 6k x 6k 15μm pixel CCD detectors. The final design review for the 4MOST LRS was successfully passed in May 2018. In 2020, a SPIE paper [1] focused on the definition of the technical requirements for all individual opto-mechanical components, the manufacturing and the deliveries up to the first assemblies in their mounts. The first LRS has now been fully integrated, aligned and tested, with both LRS foreseen for full system integration in 2022. This paper describes the long process from the integration and alignment of the sub-assemblies up to the “health-checks” performances for the entire LRS. Special emphasis is put on the procedures and tools used during this MAIT phase.
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