NASA’s Level-1 and Atmosphere Archive & Distribution System Distributed Active Archive Center (LAADS DAAC) has released two v2.1 NOAA-21 VIIRS Level-1 data collections that include calibrated radiances and geolocation. Each collection relates to image-resolution, moderate-resolution, and day-night band resolution.
This release updates the following six data products:
- VIIRS/JPSS2 Moderate Resolution Terrain-Corrected Geolocation 6-Min L1 Swath 750m (VJ203MOD)
- VIIRS/JPSS2 Imagery Resolution Terrain-Corrected Geolocation 6-Min L1 Swath 375m (VJ203IMG)
- VIIRS/JPSS2 Day/Night Band Moderate Resolution Terrain-Corrected Geolocation 6-Min L1 Swath 750m (VJ203DNB)
- VIIRS/JPSS2 Moderate Resolution 6-Min L1B Swath 750m (VJ202MOD)
- VIIRS/JPSS2 Imagery Resolution 6-Min L1B Swath 375m (VJ202IMG)
- VIIRS/JPSS2 Day/Night Band Moderate Resolution 6-Min L1B Swath 750m (VJ202DNB)
In general, Level-1 (L1) datasets are reconstructed, unprocessed instrument data at full resolution, time-referenced, and annotated with ancillary information, including radiometric and geometric calibration coefficients and georeferencing parameters computed and appended but not applied to the input Level-0 data. The L1A Geolocation products are produced by applying the geometric calibration coefficients and georeferencing parameters. The L1A data are processed to sensor units (e.g., calibrated radiances) to generate the L1B products. The VIIRS L1 data products are discipline-agnostic and provide the foundation to produce higher-level data products for all Earth science discipline domains.
The following updates define the changes implemented in the v2.1 collections.
Radiometric Calibration Changes
- Applied the Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) solar spectral irradiance.
- Improved screen functions derived from yaw maneuvers combined with regular on-orbit solar diffuser calibration data.
- Addressed the time-dependent striping mitigation for Visible Near Infrared bands M1-M3.
- Updated the Delta-C look-up table (LUT) to correct the M4 low-gain error in the pre-launch LUT.
- The recently available Day-Night Band (DNB) Mid-Gain State (MGS) Relative Spectral Response (RSR) is applied to High-Gain State (HGS) and MGS calibration, which previously only used the Low-Gain State (LGS) RSR in the earlier version v3.2.3.x.
Geolocation Accuracy
The overall geolocation accuracy for the NOAA-21 VIIRS Level-1 data is nominally good. The nadir-equivalent geolocation accuracy is within 70 m uncertainty (1-sigma Root-Mean-Squared-Error), which is well within the specified requirement of 125 m (1-sigma RMSE).