S-NPP NASA VIIRS Overview


Introduction

Land discipline Visible Infrared Imaging Radiometer Suite (VIIRS) data products developed by the National Aeronautics and Space Administration (NASA) are made available from the Land Processes Distributed Active Archive Center (LP DAAC) as product development is completed. The LP DAAC will make future announcements as these operational data become available.

VIIRS is one of five instruments on-board the Suomi National Polar-orbiting Partnership (S-NPP) satellite launched from the Vandenberg Air Force Base on October 28, 2011, at 5:48 a.m. Eastern Daylight Time (EDT). S-NPP is the first in a series of four Joint Polar Satellite System (JPSS) satellites, a collaborative mission between the National Oceanic and Atmospheric Administration (NOAA) and NASA that will carry the VIIRS instrument.

VIIRS observes the entire Earth’s surface twice each day with an equator crossing time of approximately 1:30 a.m. and 1:30 p.m. local time from NPP’s polar orbit 824 kilometers (km) (512 miles) above the Earth’s surface. The 3,000 km swath width of the VIIRS instrument, which is 710 km greater than that of Moderate Resolution Imaging Spectroradiometer (MODIS), allows for no gaps in coverage, as observed in MODIS near the equator. The VIIRS instrument provides 22 spectral bands at two spatial resolutions, 375 meters (m) and 750 m, which are resampled to 500 m, 1 km, and 0.05 degrees in the NASA produced data products to promote consistency with the MODIS heritage.

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VIIRS Naming Conventions

S-NPP NASA VIIRS Filenames

VIIRS filenames (i.e., the local granule ID) for Level 2G, Level 3, and Level 4 products follow a naming convention which provides useful information regarding the specific product.

In this example for a swath product, the filename VNP14.A2015262.1506.001.2016357171040.nc indicates:

  • VNP14: Product Short Name
  • .A2015262: Julian Date of Acquisition (AYYYYDDD)
  • 1506: Coordinated Universal Time (HHMM)
  • .001: Collection Version
  • . 2016357171040: Julian Date of Production (YYYYDDDHHMMSS)
  • .nc: Data Format (NetCDF4)

In this example for a tiled product, the filename VNP09H1.A2014001.h08v05.001.2016012234657.h5 indicates:

  • VNP09H1: Product Short Name
  • .A2014001: Julian Date of Acquisition (AYYYYDDD)
  • .h08v05: Tile Identifier (horizontalXXverticalYY) (see VIIRS Tiling System below)
  • .001: Collection Version
  • .2016012234567: Julian Date of Production (YYYYDDDHHMMSS)
  • .h5: Data Format (HDF-EOS5)

In this example for a Climate Modeling Grid (CMG) product, the filename VNP13C1.A2017001.001.2018022145650.h5 indicates:

  • VNP13C1: Product Short Name
  • .A2017001: Julian Date of Acquisition (AYYYYDDD)
  • .001: Collection Version
  • .2018022145650: Julian Date of Production (YYYYDDDHHMMSS)
  • .h5: Data Format (HDF-EOS5)

S-NPP NASA VIIRS Collection Naming Conventions

VIIRS/NPP Surface Reflectance 8-Day L3 Global 500m SIN Grid V001 is the VIIRS Long Name (i.e., Collection-Level) convention which provides useful information. For example, all products belonging to the VIIRS/NPP Surface Reflectance 8-Day L3 Global 500m SIN Grid V001 collection have the following characteristics:

  • VIIRS/NPP: Instrument/Sensor
  • Surface Reflectance: Geophysical Parameter
  • 8-Day: Temporal Resolution
  • L3: Processing Level
  • Global: Global Coverage
  • 500m: Spatial Resolution
  • SIN Grid: Sinusoidal Grid
  • V001: Collection Version
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VIIRS Temporal and Spatial Resolution

S-NPP NASA VIIRS Temporal Resolution

The higher level VIIRS land products (e.g. Level 3 and Level 4) distributed from the LP DAAC will be produced at various temporal resolutions, based on the instrument's orbital cycle. The following time steps are possibilities for the generation of VIIRS land products:

  • Daily, 8-Day, 16-Day, Monthly, Quarterly, Yearly

S-NPP NASA VIIRS Spatial Resolution

The VIIRS instruments acquire data in two native spatial resolutions:

  • Bands I1-5: 375m
  • Bands M1-16: 750m

The higher level VIIRS land products distributed from the LP DAAC are produced at three nominal spatial resolutions: 500 m, 1,000 m and 5,600 m (0.05 degrees) for Imagery bands I1-3 and Moderate bands M1-5, M7, M8, M10, M11.

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VIIRS Grid System

S-NPP NASA VIIRS Sinusoidal Tile Grid

The VIIRS tiling system is the same as the MODIS tiling system.

Image of the MODIS sinusoidal tiling system.

Level 2G, Level 3, and Level 4 S-NPP NASA VIIRS land products use this Sinusoidal grid tiling system. Tiles are 10 degrees by 10 degrees at the equator. The tile coordinate system starts at (0,0) (horizontal tile number, vertical tile number) in the upper left corner and proceeds right (horizontal) and downward (vertical). The tile in the bottom right corner is (35,17).

S-NPP NASA VIIRS Climate Modeling Grid (CMG)

The VIIRS Climate Modeling Grid (CMG) is the same as the MODIS CMG. The CMG datasets provide global coverage in a Geographic Latitude and Longitude projection at a resolution of 0.05 degrees. The geographic coordinates of the upper-left corner of the upper-left pixel of an S-NPP NASA VIIRS CMG image are -180.00 degrees longitude, 90.00 degrees latitude. The geographic coordinates of the lower-right corner of the lower right pixel are 180.00 degrees longitude, -90.00 degrees latitude.

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VIIRS Processing Levels

LP DAAC distributes land data processed to Level-2 or higher:

  • Level-2: derived geophysical variables at the same resolution and location as Level-1 source data (swath products)
  • Level-2G: Level-2 data mapped on a uniform space-time grid scale (Sinusoidal)
  • Level-3: gridded variables in derived spatial and/or temporal resolutions
  • Level-4: model output or results from analyses of lower-level data
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VIIRS Spectral Bands

Band Reflected Range (μm) Band Explanation
I1 0.6 - 0.68 Near Infrared
I2 0.85 - 0.88 Shortwave Infrared
I3 1.58 - 1.64 Medium-wave Infrared
I4 3.55 - 3.93 Longwave Infrared
I5 10.5 - 12.4 Visible/Reflective
M1 0.402 - 0.422 Visible/Reflective
M2 0.436 - 0.454 Visible/Reflective
M3 0.478 - 0.488 Visible/Reflective
M4 0.545 - 0.565 Visible/Reflective
M5 0.662 - 0.682 Near Infrared
M6 0.739 - 0.754 Near Infrared
M7 0.846 - 0.885 Shortwave Infrared
M8 1.23 - 1.25 Shortwave Infrared
M9 1.371 - 1.386 Shortwave Infrared
M10 1.58 - 1.64 Shortwave Infrared
M11 2.23 - 2.28 Medium-wave Infrared
M12 3.61 - 3.79 Medium-wave Infrared
M13 3.97 - 4.13 Longwave Infrared
M14 8.4 - 8.7 Longwave Infrared
M15 10.26 - 11.26 Longwave Infrared
M16 11.54 - 12.49 Day/Night
DNB 0.5 - 0.9 Visible/Reflective
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VIIRS Metadata

VIIRS products have two sources of metadata: the embedded HDF-EOS5 metadata, and the external Earth Observing System Data and Information System (EOSDIS) metadata, known as the EOSDIS Core System (ECS) metadata. The HDF-EOS5 metadata contains valuable information including global attributes and dataset specific attributes pertaining to the granule. An external metadata file is provided in XML format (.xml) and is provided along with the VIIRS product. This file provides a subset of the HDF-EOS5 metadata. Some key features of certain VIIRS HDF-EOS5 metadata attributes include the following:

  • The Xdim and Ydim represent the rows and columns of the data, respectively
  • The Projection and ProjParams identify the projection and its corresponding projection parameters
  • The Sinusoidal Projection is used for most of the gridded VIIRS land products, and has a unique sphere measuring 6371007.181 meters.
  • The UpperLeftPointMtrs is in projection coordinates, and identifies the very upper left corner of the upper left pixel of the image data
  • The LowerRightMtrs identifies the very lower right corner of the lower right pixel of the image data. These projection coordinates are the only metadata that accurately reflect the extreme corners of the gridded image
  • There are coordinate fields named EastBoundingCoord, WestBoundingCoord, NorthBoundingCoord and SouthBoundingCoord, which represent the latitude and longitude coordinates of the geographic tile corresponding to the data

The dataset attributes contain specific Science Dataset (SDS) information such as the data range and applicable scaling factors for the data. Information for each NASA VIIRS land data product can be found in the VIIRS Product Table.

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VIIRS Tools and Services

Data access options such as Data Pool, Earthdata Search Client, AppEEARS, and EarthExplorer can be found under Tools.

An HDF-EOS5 file contains information essential for NASA data access tools and services. Most software programs that can process standard HDF5 files can read an HDF-EOS5 file. However, it is difficult for a standard HDF5 call to interpret HDF-EOS5 geolocation or temporal information without further knowledge of the file structure.

Certain open source tools and proprietary tools are available for use with VIIRS HDF-EOS5 products and are included in the following list:

Open Source Tools

Proprietary Tools

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