***NOAA-21 VIIRS Data are Preliminary and Non-Operational***
The JPSS-2 polar-orbiting weather satellite launched from Vandenberg Space Force Base on 10 Nov 2022, becoming NOAA-21 upon reaching orbit. NOAA-21 joined NOAA-20 and S-NPP as the third JPSS series satellites, all flying with similar instruments. The Visible Infrared Imaging Radiometer Suite (VIIRS) provides global imagery at visible and infrared wavelengths at 375-m (I-bands) and 750-m (M-bands) resolution. The first science data from VIIRS were available on Dec 5, some of which were shared in this NESDIS article, consisting of visible and near-infrared bands. From this imagery, stunning 750 m True Color imagery were available, such as that in Figure 1.
Shortly after the VIIRS cryoradiator doors opened on 8 Feb 2023, science data from the infrared bands and Day Night Band became available, such as that in Fig 2 and 3, and in a NESDIS article.
The VIIRS Imagery EDR Science team has been evaluating the imagery quality, finding the imagery to be of impressive quality with very little deficiencies. After a presentation and review on Feb 23, VIIRS EDR Imagery was declared Beta Mature effective 1845 UTC 10 Feb 2023. Some examples of the remarkable NOAA-21 VIIRS EDR Imagery are shown below, including comparisons with that from S-NPP and NOAA-20.
Currently, NOAA-20 is followed by NOAA-21 by a quarter orbit (~25-min) which is followed by S-NPP by a quarter orbit (25-min), allowing for three VIIRS scans within a ~50-min period. Three-image sequences from the three instruments allow for short animations of a given phenomena, and also for one to compare the quality of the imagery, including imagery artifacts and geolocation errors.
The following 750-m resolution True Color Imagery comparison from 9 Feb 2023 over Florida and surrounding waters really exemplifies the stunning imagery available from VIIRS, including varying vegetation and ocean color, as well as the movement of clouds (Fig 4). Notice the general appearance of the imagery appears identical between the three sensors, with no shift in landmass.
The next image sequence, in animation form, looks at 375-m Band I1 Visible imagery over Puerto Rico (Fig 5). Once again, the land mass remains stationary, indicating that the geolocation is quite good across the three instruments. The three VIIRS provides an improved analysis of evolving features, with 25-mintues between scans vs the 50-min interval with two VIIRS.
Another NOAA-20/NOAA-21/S-NPP 3 VIIRS animation captures ice movement in the Alaska Region overnight in 750-m LWIR Band M15 (Fig 6).
Of course all 22 NOAA-21 VIIRS bands are investigated over a variety of scenes. For example in Fig 7, a region over Antarctica and adjacent waters is shown for all VIIRS bands
A similar animation comparing all 22 bands from NOAA-21 VIIRS is shared from over Tropical Cyclone Freddy on 13 Feb 2023 (Fig 8).
The 742-m Day Night Band/Near Constant Contrast product is one of the 22 Imagery products evaluated. The product is compared with that from NOAA-20 and S-NPP in Fig 9 from the same granules as in Fig 6. Again, the ice motion is apparent, in addition to lights associated with the Prudhoe Bay Oil Field. Aside from some more apparent striping which should be rectified with future calibration updates, the imagery looks great.
Various popular (among operational users) RGBs, which leverage the VIIRS bands, are viewed as well. Sometimes, band combinations can make certain imagery artifacts more apparent than when viewing the single band alone. Below are examples of the NOAA-21 Nighttime Microphysics RGB over Alaska (Fig 10), The Snowmelt RGB over the Northern US plains and adjacent Canada (Fig 11), True Color Imagery with Single Band M13 over Chile (Fig 12), and Day Fire RGB also over Chile (Fig 13)
Finally, NOAA-21 VIIRS Imagery captured the evolution of Tropical Cyclone Freddy from near Australia on Feb 10 all the way through Madagascar on Feb 23. The following animation leverages composites of the M15 IR band to show the 12-hourly evolution through the period.
The Provisional Maturity Review for NOAA-21 VIIRS Imagery will take place several weeks from this post.
Bill Line, NESDIS/STAR, Curtis Seaman, CIRA