Northrop Grumman Space Technology (NGST), based in southern California, is the system prime contractor for the National Polar-orbiting Operational Environmental Satellite System (NPOESS). To accomplish this next generation low-Earth orbiting environmental mission, Northrop Grumman is utilizing a multi-mission bus that satisfies spacecraft requirements for the afternoon 1330 LTAN (Equatorial crossing local time ascending node) as well as the late afternoon 1730 LTAN orbits with a single spacecraft design. This spacecraft leverages products and capabilities from the NASA Earth Observing System (EOS) Aqua and Aura spacecraft while integrating newer generation capabilities such as FireWire for accommodating advanced sensor payloads and much higher data rates than current weather satellite systems. The first NPOESS satellite will be launched in 2013 to initiate a constellation that will operate well into the following decade. This paper will provide an overview of the NPOESS spacecraft and its' capabilities.

The spacecraft structure is an upsized version of the EOS 3-meter class bus for a Delta II class of launch vehicle. The larger variant NPOESS bus maximizes the available envelope afforded by the more capable 4-meter Evolved Expendable Launch Vehicle (EELV) to host existing manifested payloads while affording extra “deck space” for upgrades to existing payloads or new payloads of opportunity as they become available. The structure is designed for low-Earth orbiting weather and environmental missions and employs a highly stable optical bench for hosting of payloads.

To accommodate current as well as emerging technologies, the spacecraft utilizes an advanced open command and data handling architecture employing a plug-and-play approach for electrical interfaces. For low rate sensor payloads, an industry standard 1553 data bus scheme is employed while high data rate payloads can use the advanced 1394 FireWire bus which was developed and qualified for space use by the NPOESS program. Evolving to a standard data bus approach allows both the spacecraft and payloads to design to a single, well-established interface with low risk, similar to the approach employed by computer manufacturers and hardware peripherals. Employing this approach enables new payloads to be added with relative ease versus legacy programs in which electrical and software interfaces were more “craft-like” in nature. If new interfaces emerge in the coming decade, the NPOESS bus has been designed with forethought to accept these new interfaces with the addition of front-end converter slices that can convert the interface for ingest and trafficability within the NPOESS command and data handling subsystem.

To deliver all classes of weather and environmental data to users, the NPOESS satellite hosts a high-rate Ka-Band stored mission data link that transmits to the worldwide network of SafetyNet™ receptors that receive NPOESS payload sensor data several times per orbit and delivers processed weather and environmental data to users within 30 minutes. Also employed are an X-Band broadcast link for large fixed users and an L-Band link for smaller mobile field terminals globally. The legacy Advanced Data Collection System (ADCS) and Search and Rescue Satellite Aided Tracking (SARSAT) system payloads are also hosted.

This presentation will provide an overview of the current requirements and capabilities for the NPOESS mission as well as flexibility to evolve over time as new payloads become available to provide valuable weather and environmental data to the global user community.