Key Features of the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) System Architecture

The National Polar-Orbiting NPOESS, a tri-agency program, supports missions of the Department of Commerce (DOC)/National Oceanic and Atmospheric Administration (NOAA), the Department of Defense (DoD), and the National Aeronautics and Space Administration (NASA). NPOESS provides a critical, timely, reliable, and high quality space-based sensing capability to acquire and process global and regional environmental imagery and specialized meteorological, climatic, terrestrial, oceanographic, solar-geophysical, and other data products. These products are delivered to national weather and environmental facilities operated by NOAA and DoD, to NASA, and to environmental remote sensing science community users to support civil and military functions. These data are also provided in real time to field terminals deployed worldwide. The NPOESS architecture is built on a foundation of affordability, and the three pillars of data quality, latency, availability. Affordability refers to an over-arching awareness of cost to provide the best value to the government for implementing a converged system; some dimensions of cost include the cost for system development and implementation, the balance between development costs and operation and maintenance costs, and the fiscal year expenditure plans that meet schedule commitments.

Data quality is characterized in terms of the attributes associated with Environmental Data Records (EDRs), and the products that are delivered to the four US Operational Centrals and field users. These EDRs are generated by the system using raw data from the space-borne sensors and spacecraft, in conjunction with science algorithms and calibration factors. Data latency refers to the time period between the detection of energy by a space-borne sensor to the delivery of a corresponding EDR. The system was designed to minimize data latency, and hence provide users with timely data. Availability refers to both data availability and system operational availability. Data availability is ensured by the way data is stored and routed throughout the system, on the spacecraft and on the ground, so that it can be retrieved and resent if the first transmittal is not successful. Operational availability is a measure of how well around-the-clock operations are supported, through the careful deployment of hot spares and fault tolerance of the system. Both types of availability are very high for the NPOESS architecture. Overall, the NPOESS architecture successfully delivers to the government a best-value solution featuring high data quality, low data latency, and high data/system availability.