The Mexico UK Sub-mm Camera for Astronomy (MUSCAT) on-sky commissioning: focal plane performance.

The MUSCAT camera is a second-generation continuum camera at the 50-m Large Millimetre Telescope (LMT) operating in the 1.1 mm band, installed in late 2021 and commissioned in early 2022. The instrument's focal plane has 1458 horn-coupled lumped-element kinetic inductance detectors (LEKIDs) divided into six arrays deposited on three silicon wafers. This work presents the preliminary on-sky performance results of the focal plane obtained during the commissioning campaign. We characterise the detector's beam size and shape, mapping the point-like source 3C 279 along the focal plane using raster scans, known as beam mapping. It also allows us to identify which resonance frequencies correspond to each detector located in the focal plane, which leads us to a more complete understanding of the behaviour of the detectors, providing us with a reasonable estimation of the array yield. Finally, we compare these results with those obtained during the characterisation of the focal plane in the Cardiff laboratory, previously reported in Tapia et al. 2020.