First VIIRS Imagery from JPSS-1

VIIRS Imagery from the Suomi-NPP satellite is the highest spatial resolution (375 m) multi-spectral imagery of any operational weather satellite to date. The polar-orbit and wide/overlapping swaths allow global coverage of the entire world every 12 hours. SNPP will now be accompanied by JPSS-1, after launch in September 2017, providing a second VIIRS image 50 minutes in advance of VIIRS from SNPP. Both satellites will occupy a polar orbit at the same local time, but a half orbit difference, on opposite sides of the earth. This will allow a double view of any location at VIIRS wavelengths including the unique Day-Night-Band (DNB) and/or Near Constant Contrast (NCC) Imagery.

Since each VIIRS instrument is unique, there is some hope that the stray light issue seen in the SNPP DNB will be reduced, or possibly eliminated. However, the plan accounts for the possibility that stray light will occur with the VIIRS on JPSS-1. The software to account for stray light already exists, however an accompanying Look-Up Table would need to be updated. That update is accounted for in the Imagery cal/val process. The checkout of JPSS-1 Imagery products will be similar to that of SNPP, but in much less time, with the expectation that Imagery will reach Provisional status at launch plus 90 days.

Another known issue with VIIRS on JPSS-1 is the non-linearity in the edge of swath DNB that was encountered in testing of VIIRS before launch. The plan to deal with this is to employ additional aggregation of pixels at the end of the DNB swath. That change will result in an extended granule, which will include measurements beyond the normal end of scan, but on only one side of the swath. This means that nadir is offset from the center of the DNB granule. Pre-launch testing has concluded that the NCC product, derived from the DNB, will be able to handle this extended granule and nadir offset.

Regardless of any pre-launch testing that has been done, the real test of the ground system and software will occur when VIIRS from JPSS-1 will be available upon opening of the VIIRS nadir doors. The Imagery Team will be working on the cal/val of JPSS-1, expecting to meet Provisional status as proposed at launch plus 90 days.

Disclaimer: The views, opinions, and findings contained in this article are those of the authors and should not be construed as an official National Oceanic and Atmospheric Administration (NOAA) or U.S. Government position, policy, or decision.