JPSS Series

The JPSS Series: New Generation of U.S. Polar-Orbiting Satellites

The Joint Polar Satellite System (JPSS) series is the new generation polar-orbiting operational environmental satellites for the U.S; it is the successor to the restructured National Polar-orbiting Operational Environmental Satellite System (NPOESS). JPSS is a collaborative program between NOAA and NASA. JPSS polar-orbiting satellites circle the Earth from pole-to-pole and cross the equator about 14 times daily in an early afternoon orbit, providing full global coverage twice a day (once during the day, and once at night).

The Suomi-National Polar Orbiting Partnership (SNPP) satellite is the first in the JPSS series. SNPP launched on October 28, 2011, and has five instruments. The most important instrument for aerosol measurements is the Visible Infrared Imaging Radiometer Suite (VIIRS). The second JPSS satellite, JPSS-1 (remaned NOAA-20 after launch), launched on November 18, 2017.  It includes five instruments similar to those on SNPP, including VIIRS.

VIIRS Aerosol Products: Legacy from MODIS

VIIRS was designed as the continuation instrument for the MODerate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites, so VIIRS has capabilities similar to MODIS. VIIRS has several advantages over MODIS, however, including higher spatial resolution (~750 m at nadir), a wide swath (~3000 km) that provides full global coverage (i.e., no orbital gaps near the equator), and minimal degradation in resolution at the edge of the swath. VIIRS aerosol products include aerosol optical thickness (AOT), smoke and dust masks, fire radiative power, and AOT-estimated surface PM2.5 concentrations.

Aerosols are suspended particles in the atmosphere that scatter and absorb sunlight. When present in high concentrations, they are easily visible in the satellite imagery. For routine detection and quantitative retrieval of the amount of aerosols, the challenge is to separate the aerosols from clouds and bright surfaces. For VIIRS aerosol products, this separation is done by using the measurements at different channels from the visible to thermal infrared. The 2.25 μm channel is transparent to most aerosols and is used to characterize the surface as dark or bright. Additionally, some surface features (e.g., soil, snow, ice) are identified by a combination of tests using visible and thermal channels. A suite of different infrared channels is used to detect clouds. Once the surface is characterized and cloudy pixels are identified, AOT is retrieved using VIIRS measured radiances in the visible bands using pre-computed look-up tables.

Applications of VIIRS Aerosol Products

The air quality community is used to using aerosol products from MODIS in various applications, and product continuity from VIIRS is continuing to feed those applications. In this way, VIIRS aerosol products will extend the use of the satellite-derived aerosol products to monitor air quality into the next two decades. For example, satellite dust/smoke detection products are used to verify the National Weather Service (NWS) operational dust/smoke guidance, and AOT products are used by the U.S. Environmental Protection Agency (EPA) and state environmental agencies in air quality assessment and the enforcement of the Exceptional Events Rule. Urban/industrial aerosol pollution, which is of utmost importance to the EPA and states for air quality standards compliance, tends to be well mixed in the planetary boundary layer and is often well correlated to the satellite-derived AOT, so VIIRS AOT can indicate the location and transport of aerosol plumes. In addition, AOT observations, when combined with a simple trajectory model, allow NWS and air quality forecasters to determine the influence of upwind aerosol loadings on local air quality.