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N Prime Satellite Gives NOAA and NASA a Fresh Look at the Weather, Climate and More
In February 2009, NASA launched NOAA-N Prime, the forty-first and last in a productive series of polar-operational environmental satellites (POES) that dates back to 1960. As it has for other satellites in the series, NASA's Goddard Space Flight Center in Greenbelt, Md., has managed the development and launch of the mission, and will transfer operational control to the National Oceanic and Atmospheric Administration (NOAA) 21 days after launch.

N-Prime's main objective is to gather critical meteorological data to aid weather forecasting. As it orbits Earth once every 102 minutes, the satellite will collect global images of cloud cover and surface features, as well as temperature and humidity profiles over sea and land. Meteorologists use such data to make short-term weather forecasts and to monitor longer-term meteorological trends such as the cycles associated with El Niño and La Niña. In addition, climatologists can use the data to better understand and quantify Earth's changing climate patterns.

To carry out its objective, the bus-sized spacecraft carries a suite of eight instruments, including: an Advanced Very High Resolution Radiometer (AVHRR) that will image surface features, such as vegetation and bodies of water; a High Resolution Infrared Radiation Sounder (HIRS) that will generate temperature and moisture profiles; two Advanced Microwave Sounding Units (AMSU) primarily for atmospheric and temperature profiles; and a Microwave Humidity Sounder (MHS) that will measure atmospheric moisture and precipitation rates.

Beyond its core meteorological and climate missions, N Prime carries instruments to collect other useful data. A space weather instrument called the Space Environment Monitor (SEM-2), for example, allows scientists to monitor potentially damaging electrons and protons in solar wind streams that can harm satellites.

image of NOAA-N Prime NASA launched NOAA-N Prime, the last of a series of polar-operational environmental satellites (POES), in February of 2009. The bus-sized spacecraft, built by NASA and operated by NOAA, collects data critical for weather forecasting.
Credit: NASA

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N Prime also carries components of the international Search and Rescue Satellite-Aided Tracking system (SARSAT). The system relays distress signals from aviators, mariners, and individuals in remote locations through satellite-to-ground stations capable of dispatching rescue teams. Since SARSAT's creation in 1982, the system is credited with saving the lives of more than 24,500 people. Enhancements in the SARSAT system will improve locating accuracy to within 100 meters (330 feet), as opposed to two to three miles with previous systems.

Although nearly identical to NOAA N, its immediate predecessor, N Prime has some notable new technologies. Engineers have added a deployable antenna that enhances the spacecraft's Data Collection System (DCS) designed to collect environmental data from unmanned buoys, instrument platforms, and balloons—as well as tagged animals—and relay it to scientists on the ground. The new Advanced DCS can send signals to individual beacons on the ground, allowing mission controllers to remotely modify beacon performance or turn them off to conserve power during idle times.

N Prime also highlights the increasing role of international collaboration in weather and environmental monitoring. In an agreement with the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), NOAA agreed to carry EUMETSAT's Microwave Humidity Sounder (MHS) on N-Prime, while EUMETSAT has agreed to carry NOAA instruments aboard a series of European-built MetOp satellites.

Built by Lockheed Martin Space Systems, N Prime was launched from the Western Range at Vandenberg Air Force Base by a United Launch Alliance two-stage Delta II rocket. The launch was managed by NASA's Launch Service Program at the Kennedy Space Center, Cape Canaveral, Fla. The satellite will send back data to NOAA's command and data acquisition centers in Fairbanks, Alaska, and Wallops Island, Va.

The launch of N Prime marks the end of a key chapter in the history of weather satellites. For decades, NASA has planned and launched weather satellites before handing them over to NOAA for operations. Under a new system, a tri-agency Integrated Program Office—including the U.S. Department of Defense, NOAA, and NASA—will manage the next generation of satellites. The first satellite in this new program, called the National Polar-orbiting Operational Environmental Satellite System (NPOESS), is slated to launch in 2013.

"It’s a bit sad to see this extremely successful program come to an end," said Mary Walker, deputy project manager of the POES program. "For nearly 50 years, NOAA and NASA have worked extremely well together on weather satellites."

Adam Voiland
NASA Goddard Space Flight Center