Global Harmonized surface reflectance products from NASA/ USGS Landsat 8 and European sentinel 2a/b missions are being processed by  NASA beginning summer 2020. HLS product support studies that require imagery every 2-3 days, including studies of vegetation phenology, as well as longer-term phenology as well as longer-term analysis of ecosystem changes. HLS global products are being produced by the Interagency Implementation and Advanced Concept Team (IMPACT) cloud computing at Marshal Space Flight Center and distributed by NASA Land process distributed Active Archive Center (LP-DAAC). 

More Info : https://earth.gsfc.nasa.gov/bio/highlights/global-harmonized-landsatsentinel-2-hls-data-products-being-released