The Simons Observatory: commissioning and performance of the large aperture telescope

The Simons Observatory is a ground-based cosmic microwave background (CMB) survey experiment consisting of three 0.5 m small-aperture telescopes (SATs) and one 6 m large-aperture telescope (LAT), located at 5200 m elevation in the Chilean Atacama Desert. The LAT contains the 2.4 m diameter Large Aperture Telescope Receiver (LATR) and its 13 Optics Tubes with more than 62,000 Transition Edge Sensor (TES) detectors spanning six frequency bands between 27 GHz and 280 GHz. Once complete, SO will be the largest and most capable CMB observatory ever built, producing arcminute resolution maps over half of the microwave sky with unprecedented sensitivity. Extensive assembly, integration, and testing work was required to successfully deploy and commission the SO LAT and LATR, with first light expected before the end of 2024. Here we provide a detailed look at the deployment, commissioning, and operation status of the SO LAT and LATR.