Harmonized Landsat and Sentinel 2

The Harmonized Landsat and Sentinel-2 (HLS) project is a NASA initiative aiming to produce a seamless surface reflectance record from the Operational Land Imager (OLI) and Multi-Spectral Instrument (MSI) aboard Landsat-8/9 and Sentinel-2A/B remote sensing satellites, respectively. The HLS products are created from a set of algorithms: atmospheric correction, cloud and cloud-shadow masking, geographic co-registration and common gridding, bidirectional reflectance distribution function (BRDF) normalization, and bandpass adjustment. The HLS Version-2.0 data are available now with global coverage (except for Antarctica). With four sensors currently in this virtual constellation, HLS provides observations once every three days at the equator and more frequently with increasing latitude. The HLS project is a collaboration between NASA and USGS, with the science team at NASA Goddard Space Flight Center supported by USGS Earth Resources Observation and Science (EROS) Center on atmospheric correction, the production team at NASA Marshall Space Flight Center, and product archive at USGS.
https://hls.gsfc.nasa.gov/documents/