The Copernicus Persistent Snow Area (PSA) product is generated annually for the entire EEA38 and the United Kingdom, based on the Fractional Snow Cover (FSC) information. It provides the extent of the persistent snow cover, i.e. the area where snow is present throughout the hydrological year with a spatial resolution of 20 m x 20 m.

This metadata refers to the PSA product distributed in raster files as tiles aligned with the Pan-European High-Resolution Layers in the European 20 m x 20 m grid (ETRS89 LAEA - EPSG: 3035). It is also available in another projection as tiles aligned with Sentinel-2 (UTM/WGS84) at 20 m x 20 m GSD. It is typically released on an annual basis with a release date in October, after the end of the hydrological year. Each product is composed of two separate GeoTIFF files corresponding to the different layers of the product, and another metadata file of the product. The first layer provides the PSA (with "no data" pixels in case of cloud conditions for all observations over the period of computation) whereas the second layer provides the QC (Quality Control, with the confidence level on the PSA layer).

PSA is one of the products of the pan-European High-Resolution Snow & Ice service (HR-S&I), which are provided at high spatial resolution (20 m x 20 m and 60 m x 60 m), from the Sentinel-2 and Sentinel-1 constellations data from September 1, 2016 onwards.

You can read more about the PSA product here: https://land.copernicus.eu/en/products/snow/high-resolution-persistent-snow-area.