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Full catalog/VJ143IA4
VJ143IA4·v002·dataset

How much sunlight the land reflects, sun-overhead (NOAA-20, 500 m, daily)

VIIRS/JPSS1 BRDF/Albedo Nadir BRDF-Adjusted Ref Daily L3 Global 500m SIN Grid V002
land NASA LPCLOUD Level 3 active HDF-EOS5
In plain English

What it measures. A daily global map of how much sunlight the land reflects when corrected to a straight-down (overhead) view, at 500 m resolution, removing the distortion that comes from the satellite seeing the surface at different angles.

How it's made. Produced daily from 16 days of VIIRS data on the NOAA-20 satellite, using a reflectance model to strip out viewing-angle effects and create a consistent, stable reflectance product designed to continue NASA's older MODIS record.

How & where you'd use it. Useful for studying land surfaces, vegetation and the planet's energy balance; the included model parameters also let researchers compute reflectance and albedo for any sun angle.

What's measured

LAND SURFACE › SURFACE RADIATIVE PROPERTIES › REFLECTANCELAND SURFACE › SURFACE RADIATIVE PROPERTIES › ANISOTROPYLAND SURFACE › SURFACE RADIATIVE PROPERTIES › ALBEDO

Coverage & cadence

  • Time span2018-01-01 → ongoing
  • Measured byNOAA-20 (VIIRS)
  • Processing levelLevel 3
  • Spatial extent-180, -90, 180, 90
  • FormatsHDF-EOS5
  • StatusACTIVE

What you can do with it

  • Track deforestation, fire scars and land-cover change
  • Monitor crop and vegetation health (NDVI/EVI)
  • Map how built-up vs. green an area is over time
Official description

The NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Nadir Bidirectional Reflectance Distribution Function (BRDF) Adjusted Reflectance (NBAR) Version 2 product provides NBAR estimates at 500 meter (m) resolution. The VJ143IA4 product is produced daily using 16 days of VIIRS data and is weighted temporally to the ninth day, which is reflected in the file name. The view angle effects are removed from the directional reflectances, resulting in a stable and consistent NBAR product. The VJ143 data products are designed to promote the continuity of NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo data product suite. The VJ143 algorithm uses the RossThick/Li-Sparse-Reciprocal (RTLSR) semi-empirical kernel-driven BRDF model, with the three kernel weights from [VJ143IA1](https://doi.org/10.5067/VIIRS/VJ143IA1.002) to reconstruct surface anisotropic effects, correcting the directional reflectance to a common view geometry (VJ143IA4), while also computing integrated black-sky albedo (BSA) at local solar noon and white-sky albedo (WSA) ([VJ143IA3](https://doi.org/10.5067/VIIRS/VJ143IA3.002)). Researchers can use the BRDF model parameters with a simple polynomial, to obtain black-sky albedo at any solar illumination angle. Likewise, both the BSA and WSA Science Dataset (SDS) variables can be used with a simple polynomial, to manually estimate instantaneous actual albedo (blue-sky albedo). Additional details regarding the methodology are available in the Algorithm Theoretical Basis Document (ATBD). The VJ143IA4 product includes six SDS variables for BRDF/Albedo mandatory quality and nadir reflectance for VIIRS imagery bands I1, I2, and I3. A low-resolution browse image is also available showing NBAR bands I1, I2, and I1 as an RGB (red, green, blue) image in JPEG format. Known Issues * For complete information about known issues please refer to the [MODIS/VIIRS Land Quality Assessment website](https://landweb.modaps.eosdis.nasa.gov/knownissue?sensor=VIIRS).

Get the data

vj143ia4_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="VJ143IA4",
    version="002",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from LPCLOUD
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.