Background
The Satellite Needs Working Group (SNWG)-2016 process supported the production of a global Harmonized Landsat and Sentinel-2 (HLS) surface reflectance product. HLS is derived from re-projecting top-of-atmosphere reflectance from Landsat 8/9 and Sentinel-2 A/B/C onto a common grid, resulting in two surface reflectance products (L30: Landsat and S30: Sentinel-2, 30 m products). Science-quality products for HLS v2.0, which include atmospheric compensation, look angle adjustment, and bandpass normalization, were released globally in August 2021.
Surface reflectance information is routinely used to assess vegetation type, long-term changes in land use, disasters, and season health as inferred through vegetation greenness. This information is obtained through "vegetation indices" that relate multiple HLS bands to specific parameters of interest as an instantaneous value, time series, or anomaly. Agencies indicated an interest in the following indices:
- Normalized Difference Vegetation Index (NDVI)
- Enhanced Vegetation Index (EVI)
- Soil-Adjusted Vegetation Index (SAVI)
- Modified Soil-Adjusted Vegetation Index (MSAVI)
- Normalized Difference Moisture Index (NDMI)
- Normalized Difference Water Index (NDWI)
- Normalized Burn Ratio (NBR)
- Normalized Burn Ratio-2 (NBR2)
- Triangular Vegetation Index (TVI)
In addition, decreasing the data latency of the widely-used HLS product will provide significant benefits across agencies as well. The current data latency is 3-4 days and is constrained by Moderate Resolution Imaging Spectroradiometer (MODIS) atmospheric correction data. This multi-day data latency makes the HLS data less useful to many agencies that utilize satellite data for rapidly changing phenomena (i.e., fires, floods, crops, etc.) and for operational needs.
To meet this need, NASA is exploring the ability to decrease the latency by using an alternative auxiliary data source required for atmospheric correction. Currently, the HLS processing pipeline uses the Visible Infrared Imaging Radiometer Suite (VIIRS) data products for atmospheric correction. This solution will explore alternate auxiliary products for atmospheric correction that are published at lower latency compared to VIIRS data products to produce HLS data with a median latency of 6 hours.
Status
Currently in Development, but Some Data are Available Now
The HLSL30 archive extends back to April 2013. The HLSS30 archive was completed on June 6, 2023, and extends back to December 2015. The products are generated as cloud optimized GeoTIFFs (COGs), with supporting tutorials offered by NASA's Land Processes Distributed Active Archive Center (LP DAAC). Dynamic band combinations and calculations were recently released as a beta release in NASA Worldview allowing for customized visualizations of HLS data back to March 2022. See an example in NASA Worldview.
Indices are also being generated for the HLS archive (December 2015 for Sentinel-2 and April 2013 for Landsat) and will continue forward with future HLS acquisitions as part of the HLS production system thereby increasing overall produce efficiency while decreasing product latency and reducing duplicative processing efforts across the United States (U.S.) government. The forward processing of HLS-Vegetation Indices (VI) began in February 2025, and historical data processing began in August 2025.
In addition, NASA is currently investigating how to develop low-latency HLS products in the most technologically feasible way. Investigations into the feasibility of National Centers for Environmental Prediction (NCEP) water vapor and ozone products for atmospheric correction and their effects on HLS data quality are currently ongoing. Two options for these solutions that are being evaluated are:
- The creation of a provisional low-latency product that would be replaced with the science-quality product is released
- A new processing approach that would retain the overall science quality of the data but decrease the overall HLS processing times
Solution Characteristics
| Products | HLSL30 | HLSS30 | HLSL30_VI | HLSS30_VI | HLSL30_LL | HLSS30_LL |
|---|---|---|---|---|---|---|
| Platform | Landsat 8/9 | Sentinel-2A/B/C | Landsat 8/9 | Sentinel-2A/B/C | Landsat 8/9 | Sentinel-2A/B/C |
| Instrument | Operational Land Imager (OLI) | Multispectral Instrument (MSI) | OLI | MSI | OLI | MSI |
| Processing Level | 3 | 3 | 4 | 4 | 1C | 1C |
| Temporal Coverage | April 11, 2013 - Present | Nov. 29, 2015 - Present | April 11, 2013 - Present | Nov. 29, 2015 - Present | To Be Determined (TBD) | TBD |
| Temporal Resolution | 1.6 days | 1.6 days | 1.6 days | 1.6 days | Daily | Daily |
| Latency | 2 days | 2 days | 2 days | 2 days | Less than 6 hours | Less than 6 hours |
| Spatial Coverage | Global Land (excludes Antarctica) | Global Land (excludes Antarctica) | Global Land (excludes Antarctica) | Global Land (excludes Antarctica) | Global Land (excludes Antarctica) | Global Land (excludes Antarctica) |
| Spatial Resolution | 30 m | 30 m | 30 m | 30 m | 30 m | 30 m |
| Data Format | Cloud-optimized GeoTIFF | Cloud-optimized GeoTIFF | Cloud-optimized GeoTIFF | Cloud-optimized GeoTIFF | Cloud-optimized GeoTIFF | Cloud-optimized GeoTIFF |
Societal Impact
The HLS project enables global observations of the land every 1.6 days, which is pivotal for improved monitoring of land surface changes, disaster response, and agricultural management. The HLS-VI products include a suite of 9 vegetation indices that are key for global monitoring of vegetation health, soil properties, and water levels. Considering the widespread usage of HLS among federal agencies, a low latency version of HLS — here defined as a 6 hour latency — will also enhance agencies' ability to respond to wildfires, earthquakes, droughts, oil spills, etc.
Below are "Data in Action" stories for HLS that demonstrate its benefit to end users.
Solution Resources
Need help using this solution? For more information about HLS solutions visit the following resources:
- HLS data: HLSS30, HLSL30
- HLS-VI data: HLSS30_VI, HLSL30_VI
- Training Resources: HLS
- Training Resources: HLS-VI