About HLS

Overview

Harmonized Landsat and Sentinel-2 (HLS) is a NASA initiative that creates a seamless product from the Operational Land Imager (OLI) beginning with Landsat 8 in 2013 and Multi-Spectral Instrument (MSI) aboard Sentinel-2 satellites in 2015. HLS Version 2.0 (V2.0) is the most recent version of these data and was found to have a global median repeat frequency of <1.4 days in 2025 with 5 satellites (Landsat 8/9, Sentinel-2 A/B/C). All HLS data are science quality, analysis ready, and freely available to users with a two- to three-day latency.

HLS V2.0 is one of NASA’s most downloaded data products. Its high temporal repeat and global coverage make it a valuable resource for monitoring changes to the Earth’s surface, especially those that occur on short timescales. It serves as the basis for various monitoring systems tracking land surface change worldwide.

The Origins of the Algorithm

The story of HLS begins before the launch of Sentinel-2A in 2015. Jeffrey Masek, the Deputy Project Scientist for Landsat 8 at the time, led a group of researchers who wanted to find a way to harmonize Landsat data with other satellite data. Their aim was to create a “virtual constellation” similar to how weather satellites operate.

In March 2025, wildfires burned through South Korea, resulting in heavy vegetation loss. [left] Output of the DIST-ALERT product on NASA Worldview from May 8, 2025, with vegetation loss in percent flagged with varying levels of confidence. Yellow and red represent areas with confirmed vegetation cover losses of <50% and ≥50%, respectively. [right] Natural-color image captured by the Multi-Spectral Instrument (MSI) aboard Sentinel-2C on May 8, 2025. The large brown burn scar in the center of the image corresponds to vegetation loss detected by DIST-ALERT. It stands in contrast to the surrounding green vegetation.

Harmonized Landsat and Sentinel-2: Collaboration Drives Innovation

The Harmonized Landsat and Sentinel-2 (HLS) dataset is one of NASA’s most-downloaded data products. Learn about the history and future of this groundbreaking project.

The Collaboration Behind HLS

The HLS algorithm was developed through interagency and international collaboration. NASA’s Goddard Space Flight Center (GSFC) and Marshall Space Flight Center (MSFC) worked alongside the University of Maryland (UMD), U.S. Geological Survey (USGS), and the European Space Agency (ESA) to harmonize the data from Landsat and Sentinel-2 satellites. By harmonizing, researchers enable data users to directly and seamlessly use observations from the two different sources.

The HLS algorithm development is led by the HLS Science Group at GSFC and is ported and operated by ODSI, located at NASA’s Marshall Space Flight Center in Huntsville, AL. The data products are archived at and distributed by the Land Processes Distributed Active Archive Center (LP DAAC), which is a partnership between NASA and the USGS.

A year of NDVI (Normalized Difference Vegetation Index) data of farm fields south of Columbus, Nebraska, on the left upper edge of the video. The Platte River flows west to east along the top. David City is in the center and Shelby is in the lower left, partially obscured by the legend. In this visualization, red is bare soil and green indicates healthy, growing vegetation. The animation runs from January 1 to December 30, 2016.

The USGS and ESA provide NASA with Landsat and Sentinel-2 data at a global scale in order for NASA to produce HLS data as quickly as possible.

What began as a research question with an experimental product evolved into an operational global project with the involvement of the Satellite Needs Working Group (SNWG). SNWG is an interagency effort to develop solutions that address Earth observation needs of civilian federal agencies. Every two years, SNWG conducts a survey of federal agencies to see how their work could benefit from satellite data. The HLS surface reflectance product was an outcome of the very first SNWG solution cycle in 2016, in response to federal agencies’ requests for more frequent observations of Earth’s land surface. This product was expanded, following additional SNWG requests in 2020 and 2022. The 2020 cycle saw the creation of nine HLS-derived vegetation indices that are nearing completion of historical product creation in 2026, and the 2022 cycle aimed for a six-hour latency product, which is currently in development.

HLS Team

HLS Science Group

BRDF, Band Pass Adjustment, Product Evaluation

NASA GSFC Biospheric Sciences Laboratory

Land Surface Reflectance Code (LaSRC)

NASA GSFC Terrestrial Information Systems Laboratory

Function of Mask (Fmask)

UCONN Global Environmental Remote Sensing Laboratory
  • Zhe Zhu – FMask Lead Algorithm Developer
  • Shi Qiu – FMask Co-Developer
  • Kexin Song – TIF (Time-series Image Fusion) Lead Developer

Landsat Science Support Team

NASA GSFC Biospheric Sciences Laboratory

HLS Production

NASA MSFC (UAH Earth System Science Center Laboratory for Applied Science)

  • Madhu Sridhar – HLS Production Lead
  • Trang Vo – HLS Production Evaluation and Support
  • Lavanya Ashokkumar – HLS Production Documentation Support

NASA MSFC (Development Seed)

  • Sean Harkins – HLS Lead System Engineer
  • Christopher Holden –  HLS Lead Cloud Engineer

NASA’s SNWG Implementation Team Management Office (NSITE MO)

NASA HQ

  • Natasha Sadoff – NSITE Program Manager

NASA MSFC

  • Pontus Olofsson – NSITE Project Scientist 
  • Sean Gregory – NSITE Project Manager
  • Emily Adams (PCI Productions) – NSITE Communications Strategist
  • Cherrelle Tucker (Barrios) – NSITE Project Coordinator
  • Stephanie Jimenez (UAH ESSC) – NSITE/HLS Stakeholder Engagement
  • Anita LeRoy (UAH ESSC) – Co-Design and Stakeholder Engagement Lead   
  • Katrina Virts (UAH ESSC) – Deputy Project Scientist/Assessment Lead
  • Jenny Wood (UAH ESSC) – Systems Engineer

OPERA-HLS Production

NASA JPL

University of Maryland Global Land Analysis & Discovery (GLAD) Lab

United States Geological Survey (USGS)

  • John Jones – OPERA-DSWX Principal Investigator

Land Processes Distributed Active Archive Center (LP DAAC)

USGS

  • Cole Krehbiel – LP DAAC Project Scientist
  • Jared Beck – LP DAAC Science Data Lifecycle Lead
  • Matt Martens – LP DAAC Operations Engineering Lead

EarthData Global Imagery Browse Services (GIBS)

NASA Earth Science Data and Information Systems (ESDIS)

  • Natalie Pressley
  • Alex De Luca