Harmonized Landsat and Sentinel 2 Expands Global Earth Monitoring Capabilities

Harmonized Landsat and Sentinel 2 Expands Global Earth Monitoring Capabilities
by Clarence Oxford
Los Angeles CA (SPX) Aug 26, 2025

A collaboration between NASA, the U.S. Geological Survey (USGS), and the European Space Agency (ESA) has transformed land monitoring by integrating Landsat and Sentinel-2 satellite data into a unified product known as Harmonized Landsat and Sentinel-2 (HLS). This joint initiative addresses the long-standing challenge of Landsat's eight-day revisit cycle, which limits the ability to track rapid events such as floods, fires, and storm damage.

Sentinel-2A's launch in 2015, followed by Sentinel-2B in 2017, provided optical data compatible with Landsat. NASA's Goddard Space Flight Center led efforts to harmonize these datasets, producing HLS. The latest release, HLS Version 2.0 (V2.0), delivers near-global coverage at 30-meter resolution with a median repeat frequency of 1.6 days in 2022. The addition of Sentinel-2C data further increases observation frequency, enhancing applications in agriculture, disaster response, and environmental monitoring.

The HLS project emerged from the Satellite Needs Working Group (SNWG), an interagency effort to identify federal data requirements. Since 2016, SNWG has supported HLS as an operational solution. Products have expanded to include vegetation indices and near real-time applications. Federal agencies including USDA and FEMA now rely on HLS for monitoring crop health, managing grazing, and directing disaster aid.

In July 2025, researchers detailed the technical improvements of HLS V2.0 in Remote Sensing of Environment. The dataset spans all landmasses except Antarctica from 2013 onward and includes significant advances in atmospheric correction, cloud masking, and reflectance harmonization. These refinements enable Sentinel-2 and Landsat data to be used interchangeably for consistent surface reflectance monitoring.

HLS V2.0 is already powering global land change detection. The DIST-ALERT system, developed through NASA's OPERA project in partnership with the University of Maryland, identifies vegetation disturbances from deforestation, logging, urbanization, fire, and floods within six hours of new data availability. Similarly, the Dynamic Surface Water eXtent (DSWx) product suite maps lakes, rivers, and flood events worldwide.

These capabilities support both research and policy. Logging companies use DIST-ALERT outputs to verify compliance with regulations, while the U.S. Census Bureau monitors fast-growing communities between decennial surveys. Brazil's deforestation alert systems, alongside Global Forest Watch, also integrate harmonized data to improve tropical forest monitoring.

Looking forward, NASA and partners continue refining algorithms to improve harmonization and cloud masking while developing a six-hour low-latency HLS product. Upcoming Landsat and Sentinel missions will expand these capabilities further, ensuring more frequent, high-quality Earth observations for global land monitoring.

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