The Cross-track Infrared Sounder (CrIS) is one of the critical instruments within the NPOESS system. Its mission is to collect atmospheric profiles for temperature, moisture, and pressure within the earth's atmosphere. The sounding accuracy of CrIS will be well beyond the capabilities of current operational sounders. The purpose of this paper is to discuss the evolution of the CrIS instrument design, describe its key performance parameters (both in terms of instrument-level and mission-level performance), and show a performance comparison between the current-generation HIRS sounder and the CrIS instrument. Development plans for CrIS are also discussed.

Since the 1970s, the United States has relied on two separate low-earth-orbiting (LEO) meteorological satellite systems (POES for civilian users and DMSP for military users) to provide remote sensing data that is used for weather forecasting and other critical applications. Because these two systems have sensors that share many similar characteristics, a decision was made in the early 1990s to "converge" these two meteorological systems into a single system for the next century. This system, known as NPOESS (National Polar-orbiting Operational Environmental Satellite System), is to provide a single low-earth orbiting satellite system that can fulfill the missions of both the civilian and military users. The Crosstrack Infrared Sounder (CrIS) is one of the primary sensors within the NPOESS system. Its mission is to collect upwelling infrared spectra at very high spectral resolution, and with excellent radiometric precision. The goal of CrIS to produce infrared spectra with much higher spectral resolution than current sounders such as HIRS, as shown in Figure 1. The higher resolution data can then be used to produce soundings with improved accuracy and vertical resolution. The CrIS data will be merged with microwave data from another sensor on the NPOESS platform to construct highly accurate temperature, moisture, and pressure profiles of the earth's atmosphere. Collectively, the CrIS and microwave sensor are referred to as the CrIMSS (Crosstrack Infrared and Microwave Sounding Suite). The profiles produced by this suite are a primary input to numerical weather forecast models, and their improved accuracy offer enhanced forecast accuracy on a global basis.