## 2 Joint Polar Satellite System  
The Joint Polar Satellite System (JPSS) is a new generation polar-orbiting operational environmental satellite system in the United States ([[https://www.jpss.noaa.gov/mission_and_instruments.html](https://www.jpss.noaa.gov/mission_and_instruments.html)]([https://www.jpss.noaa.gov/mission_and_instruments.html](https://www.jpss.noaa.gov/mission_and_instruments.html)), accessed on 25 August 2021). JPSS is a collaborative program between the National Oceanic and Atmospheric Administration (NOAA) and its acquisition agent, the National Aeronautics and Space Administration (NASA). The Suomi-National Polar-Orbiting Partnership (SNPP) satellite, launched on 28 October 2011, is the prototype of the JPSS program, originally designed as a preparatory program for the aborted National Polar-orbiting Operational Environmental Satellite System (NPOESS). The first JPSS satellite (JPSS-1) was launched on 18 November 2017. After successful commissioning, JPSS-1 was renamed NOAA-20. NOAA-20 leads SNPP by 50 min in the same orbit. The JPSS-2 launch date is currently scheduled in 2022 ([[https://www.wmo-sat.info/oscar/satellites/view/jpss_2](https://www.wmo-sat.info/oscar/satellites/view/jpss_2)]([https://www.wmo-sat.info/oscar/satellites/view/jpss_2](https://www.wmo-sat.info/oscar/satellites/view/jpss_2)), accessed on 25 August 2021). JPSS-3 and JPSS-4 are scheduled in 2027 and 2032, respectively. JPSS will provide continuity of critical, global observations of Earth's atmosphere, oceans, and land through 2038. SNPP and all JPSS satellites observe the Earth's surface twice a day, once during the day and once at night, flying 830 km high in a polar orbit around 1:30 p.m., crossing the equator at local time. Both SNPP and NOAA-20 have continued supporting accurate forecasts and provide advanced warning for severe weather, such as hurricanes, deadly tornado outbreaks, heat waves, droughs and floods, snowfall, and wildfires. The satellites carry the Advanced Technology Microwave Sounder (ATMS), the Cross-track Infrared Sounder (CrIS), the Visible and Infrared Imaging Radiometer Suite (VIIRS), the Ozone Mapping and Profiler Suite (OMPS), and the Clouds and the Earth's Radiant Energy System (CERES) on the same platform. The ATMS is a cross-track scanner with 22 channels of temperature and humidity sounding measurements over a frequency range from 23 to 183 GHz. The ATMS provides sounding observations for atmospheric temperature, moisture, and clouds as well as surface temperature, snow, and ice [3]. All channels are sampled every 1.1\({}^{\circ}\) at 96 scan positions, with a cross track swath width of 2500 km, which is significantly wider [4] than AMSU-A or MHS. ATMS channels 1 and 2 have a large beam width (low spatial resolution) of 5.5 degrees; channels 3 to 16 have a medium beam width of 2.2 degrees; and channels 17 to 22 have a small beam width of 1.1 degrees. The CrIS is a Fourier transform spectrometer (Michelson interferometer) with 2223 un-apodized (2211 Hamming apodized) spectral channels over three wavelength ranges: long-wave infrared (LWIR), middle-wave infrared (MWIR), and short-wave infrared (SWIR) [5]. CrIS scans a 2200 km swath width (\(\pm 50^{\circ}\)) with 30 Earth scene views (i.e., field of regards). Each scene consists of nine fields of view, arrayed as a 3 \(\times\) 3 array of 14 km diameter spots at a nadir spatial resolution. The CrIS provides hyperspectral measurements for atmospheric sounding of three-dimensional temperature, pressure, moisture profiles, and trace gases: carbon dioxide, monoxide, ozone, and methane. VIIRS succeeds the NOAA Advanced Very HighResolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Aqua and Terra satellites.