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The Jet Propulsion Laboratory (JPL) is best known for planetary exploration but is also heavily involved in Earth science and has in recent years become one of the premier centers for atmospheric science related to infrared and microwave satellite sounders such as the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU) and the Advanced Technology Microwave Sounder (ATMS), as well as aircraft based microwave sounders such as the High Altitude MMIC Sounding Radiometer (HAMSR) and the development of future sounders such as an infrared CubeSat system (CIRAS) and a geostationary microwave sounder (GeoSTAR). We give a brief overview of these sensors and focus on the development and assessment of sounder data products, which include vertical profiles of temperature and water vapor, cloud and surface parameters, and in the case of infrared sounders also trace gas estimates and for microwave sounders precipitation as well. The baseline AIRS data product “retrieval system” was developed by the AIRS science team and has been undergoing continuous maintenance and upgrade in close collaboration with the sounder team at JPL. To support that process, the JPL team has developed a broad range of assessment tools and techniques, which can be applied to data from other sounders as well and can range from simple “sanity check” analysis to thorough “validation” analysis. An example of the less complex testing is the preliminary assessment of products generated by new retrieval systems operating on data from the Cross-track Infrared Sounder (CrIS) and the Advanced Technology Microwave Sounder (ATMS) flying on the Suomi NPP and JPSS satellites. These retrieval systems are developed by individual investigators funded by NASA research grants and are delivered to a Sounder “Science Investigator Processing System” (SIPS) located at JPL for integration, testing and delivery to a NASA data processing center and eventual release to the public, but only limited resources are available to the SIPS for the assessment, which therefore must be relatively superficial. An example of thorough assessment is the quantification of the impact on AIRS products of the failure of the AMSU-A2 microwave sounder 2 years ago. The baseline AIRS retrieval system used initially data from the companion microwave sounders, the Humidity Sounder for Brazil (HSB), AMSU-A1 and AMSU-A2, to provide a “first guess” and support “cloud clearing”. As these instruments suddenly failed (HSB) or gradually deteriorated (AMSU), some effort was devoted to develop a version that did not depend on microwave data. It was considered somewhat inferior to the baseline system and was kept in reserve and therefore not fully assessed. When AMSU-A2 failed, this AIRS-only system became the primary version, and a substantial effort was undertaken to fully assess its performance. We discuss details of that assessment. These capabilities have resulted from substantial investments NASA has made over the years in support of AIRS and can now be applied to next-generation systems as well.
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