VNP46A1 - VIIRS/NPP Daily Gridded Day Night Band 500m Linear Lat Lon Grid Night

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 enables 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.

VNP46A1 is the short-name for the daily, top-of-atmosphere, at-sensor nighttime radiance product whose long-name is VIIRS/NPP Daily Gridded Day Night Band 15 Arc-Second Linear Lat. Lon. Grid Night. It contains 28 Science Data Sets (SDS) that include sensor radiance, zenith and azimuth angles (at-sensor, solar, and lunar), cloud-mask flags, time, shortwave IR radiance, brightness temperatures, VIIRS quality flags, moon phase angle, and moon illumination fraction. It also provides Quality Flag (QF) information specific to the cloud-mask, VIIRS moderate-resolution bands M10, M11, M12, M13, M15, M16, and DNB.

This v2.0 VNP46A1 collection is provided in standard Hierarchical Data Format–Earth Observing System (HDF-EOS5) format. This collection, which starts from January 19, 2012, and forward 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.

The 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 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.

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.