VNP46A2 - VIIRS/NPP Gap-Filled Lunar BRDF-Adjusted Nighttime Lights Daily L3 Global 500m Linear Lat Lon Grid

The Suomi National Polar-orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS) supports a Day-Night Band (DNB) sensor that provides global, daily measurements of nocturnal visible and near-infrared (NIR) light that are suitable for Earth system science and applications. The VIIRS DNB’s ultra-sensitivity in lowlight conditions enable us to generate a set of science-quality nighttime products that manifest substantial improvements in sensor resolution and calibration when compared to the previous era of Defense Meteorological Satellite Program/Operational Linescan System’s (DMSP/OLS) nighttime lights image products. Such improvements allow the VIIRS DNB products to better monitor both the magnitude and signature of nighttime phenomena, and anthropogenic sources of light emissions.

VNP46A2 is the short-name for the daily, moonlight- and atmosphere-corrected Nighttime Lights (NTL) product whose long-name is VIIRS/NPP Gap-Filled Lunar BRDF-Adjusted Nighttime Lights Daily L3 Global 500m Linear Lat Lon Grid. It contains nine Science Data Sets (SDS) that include the following:

1. DNB BRDF-Corrected NTL
2. DNB Lunar Irradiance
3. Gap-Filled DNB BRDF-Corrected NTL
4. Latest High-Quality Retrieval
5. Mandatory Quality Flag
6. Cloud Mask Quality Flag
7. Snow/Ice Flag
8. Latitude
9. Longitude

This version 2.0 product contains certain changes and differences relative to the previous v1.0 collection. They include the following:

1. The v2.0 Day-Night Band (DNB) radiance data format has changed from unsigned integer in v1.0 to floating-point format to prevent saturation in cases such as extremely bright gas flares with radiance values exceeding 6553.5 nW·cm⁻²·sr⁻¹. The maximum value for an unsigned integer format is 65535.
2. The v1.0 VNP46A2 collection is produced exclusively for land surfaces, whereas v2.0 VNP46A2 is generated for both land and water surfaces.
3. In the v2.0 collection, the VNP46A2 Mandatory_Quality_Flag layer has been updated to 0 for high quality and 1-5 for poor quality. Besides, the v2.0 Mandatory_Quality_Flag includes additions for lunar eclipse (qa=3), aurora (qa=4), and glint (qa=5). In v1.0, the Black Marble products are generated with solar zenith angles greater than 108 degrees. In the new v2.0, the range is expanded to include solar zenith angles greater than 102 degrees. Also, the quality for solar zenith angles between 102 and 108 degrees is assigned a value of 2 in the Mandatory_Quality_Flag.
4. The SNPP DNB experienced degradation after launch, whereas the NOAA-20 and NOAA-21 DNB remain stable. In v2.0, the yearly DNB spectral response functions are applied to the SNPP Black Marble product.

This v2.0 VNP46A2 collection is provided in standard Hierarchical Data Format-Earth Observing System (HDF-EOS5) format. This collection starts from January 19, 2012, and forward. The VNP46A2 product has been validated through various field campaigns of opportunity supported under the Group on Earth Observations (GEO) Human Planet Initiative’s Nighttime Product Validation (NPV) task. Additionally, the VNP46 product suite comes with ancillary and quality assessment layers indicating sources of error from the calibration, cloud mask, snow flag, and lunar irradiance, etc.

Processing Chain Provenance
This section instructs users regarding where to find the source locations for three provenance-specific information artifacts in the global metadata attributes.

Processing steps used to generate the SNPP VIIRS VNP46 product: The data product inputs, the algorithm processing flow, and all other pertinent details that help create the VIIRS Nighttime Lights products are described in the following two sources:

1. The The Black Marble User Guide (Version 2.0, October 2024)
2. The Black Marble Algorithm Theoretical Basis Document (Version 1.1, July 2020)

The data producer's name and email: This information is available in the global metadata attributes.

The production software (PGE) version used: The processing software used to generate the product is called a Product Generation Executable or PGE, and is identified via the following two pieces of information in the global metadata attributes:

1. PGE_Name, which is an alphanumeric value, e.g., “PGE554”
2. PGE Version, which is a numeric value, e.g., “1.0.10”

The PGE name and its version help associate the exact production software that was used to generate any specific version of the data product.