Both VNP46 products use the standard suite of VIIRS land products as input and are integrated as part of NASA's Black Marble processing chain which contains both daytime and nighttime branches. For the daytime branch, a modified version of the operational VIIRS surface reflectance algorithm (Roger et al., 2016; Vermote et al., 2014) is used to generate the DNB surface bidirectional reflectance factor (BRF) using NASA's Level 1B calibrated radiance product as input (i.e., 6-minute granules, or 2366 km along track and ~3100 km across-track). Level 2G DNB surface reflectance is then generated by performing spatial and temporal aggregation to 15 arc second grid cells over daily time periods (Campagnolo et al., 2016; Pahlevan et al., 2017; Wolfe et al., 1998; Yang and Wolfe, 2001). Daily Level 3 DNB BRDF/Albedo data are then retrieved using the heritage MODIS/VIIRS algorithm (MCD43/VNP43) (Liu et al., 2017, Liu et al., 2017; Wang et al., 2018), and corresponding snow flags are estimated using the VIIRS Normalized Difference Snow Index (NDSI) algorithm (VNP10) (Riggs et al., 2016, Riggs et al., 2017). The NDVI and NDSI values are used to determine the growing, dormant, and snow periods to routinely update the a priori global database of the DNB BRDF product (Cescatti et al., 2012; Liu et al., 2017, Liu et al., 2017; Román et al., 2009). Surface bidirectional reflectance factor from the VIIRS I1 (red) and I2 (NIR) channels is used to obtain daily estimates of LAI (Knyazikhin et al., 1999; Park et al., 2017; Xiao et al., 2016). The retrieved leaf area index and clumping index values are then used to calculate the gap fraction probability (Pgap).

Black Marble VNP46A1 product input files

Input File	Description
VNP02DNB	VIIRS/NPP Day/Night Band 6-Min L1B Swath 750m (L1B DNB)
VNP02MOD	VIIRS/NPP Moderate Resolution 6-Min L1B Swath 750m (L1B moderate bands)
NPP DNBN	VIIRS L2G DNB radiance
NPP DNBN angles	VIIRS L2G DNB angles
NPP MOD	VIIRS L2G moderate bands M10, M11, M12, M13, M15, M16
NPP PTDN	VIIRS DNB pointer files
The standard VIIRS Cloud Mask (VCM)	VIIRS cloud mask

The nighttime branch is the path that actually generates the final VNP46 products. We begin with the at-sensor TOA nighttime radiance (VNP46A1), along with the corresponding nighttime cloud mask, multiple solar/viewing/lunar geometry values (including moon-illuminated fraction and phase angles), and the daily snow and aerosol status flags. These science data sets (SDS) enable open access to the primary inputs used to generate the NASA Black Marble NTL time series record, thus ensuring reproducibility of the final outputs. A series of temporal and spatial gap-filling techniques are also employed to improve the coverage of the VNP46 NTL product.

The NASA Black The daily at-sensor TOA nighttime radiance product (VNP46A1) is available at 15 arc second resolution from January 2012 onward. The 15 arc second VNP46A1 product contains 26 SDS layers, including sensor radiance, zenith and azimuth angles at sensor, solar, and lunar, cloud mask flag, time, shortwave IR radiance, brightness temperatures, VIIRS quality flags, moon phase angle, and moon illumination fraction. The table below details the information within the product layers.

Scientific datasets included in the VNP46A1 daily at-sensor TOA nighttime radiance product

Scientific Datasets (SDS HDF Layers)	Units	Description	Bit Types	Fill Value	Valid Range	Scale Factor	Offset
DNB_At_Sensor_Radiance	nW cm-2 sr -1	At-sensor DNB radiance	16-bit unsigned integer	65535	0 - 65534	0.1	0.0
Sensor_Zenith	Degrees	Sensor zenith angle	16-bit signed integer	-32768	-90 - 90	0.01	0.0
Sensor_Azimuth	Degrees	Sensor azimuth angle	16-bit signed integer	-32768	-180 - 180	0.01	0.0
Solar_Zenith	Degrees	Solar zenith angle	16-bit signed integer	-32768	0 - 180	0.01	0.0
Lunar_Zenith	Degrees	Lunar zenith angle	16-bit signed integer	-32768	-180 - 180	0.01	0.0
Lunar_Azimuth	Degrees	Lunar azimuth angle	16-bit signed integer	-32768	0 - 180	0.01	0.0
Glint_Angle	Degree	Moon glint angle	16-bit signed integer	-32768	-180 - 180	0.01	0.0
UTC_Time	Decimal hours	UTC time	32-bit floating point	-999.9	0-24	1.0	0.0
QF_Cloud_Mask	Unitless	Cloud mask status	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
QF_DNB	Unitless	DNB quality flag	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
Radiance M_10	Wm-2 μm-1 sr-1	Radiance in band M10	16-bit unsigned integer	65535	0 - 65534	0.0013045005	-0.04
Radiance M_11	Wm-2 μm-1 sr-1	Radiance in band M11	16-bit unsigned integer	65535	0 - 65534	0.00058	-0.02
Brigthness Temperature M_12	Kelvin	Brigthness Temperature of band M12	16-bit unsigned integer	65535	0 - 65534	0.002518946	203.0
Brigthness Temperature M_13	Kelvin	Brigthness Temperature of band M13	16-bit unsigned integer	65535	0 - 65534	0.002518946	203.0
Brigthness Temperature M_15	Kelvin	Brigthness Temperature of band M15	16-bit unsigned integer	65535	0 - 65534	0.004120439	111.0
Brigthness Temperature M_16	Kelvin	Brigthness Temperature of band M16	16-bit unsigned integer	65535	0 - 65534	0.004257787	103.0
QF_VIIRS_M10	Unitless	Quality flag of band M10	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
QF_VIIRS_M11	Unitless	Quality flag of band M11	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
QF_VIIRS_M12	Unitless	Quality flag of band M12	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
QF_VIIRS_M13	Unitless	Quality flag of band M13	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
QF_VIIRS_M15	Unitless	Quality flag of band M15	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
QF_VIIRS_M16	Unitless	Quality flag of band M16	16-bit unsigned integer	65535	0 - 65534	N/A	N/A
Moon_Phase_Angle	Degrees	Moon ohase angle	16-bit signed integer	-32768	0 - 180	0.01	0.0
Moon_Illumination_Fraction	Percentage	Moon ilumination fraction	16-bit signed integer	-32768	0 - 100	0.01	0.0
Granule	Unitless	Nunber of selected granule	8-bit unsigned integer	255	0 - 254	1.0	0.0