[Fact Sheets]

FS-2000-06-006-GSFC

NOAA-L Continues Polar Operational Environmental Satellite Series

Since the 1960s, NASA has developed polar-orbiting operational environmental observation satellites for the National Oceanic and Atmospheric Administration (NOAA). NOAA-L, the latest NOAA spacecraft, is scheduled for launch in the summer of 2000.

The NOAA satellites carry instruments that observe our Earth and provide global data for NOAA’s operational user requirements including short- and long-range weather forecasts. The operational system consists of two polar-orbiting satellites. One crosses the equator at roughly 7:30 a.m. and 7:30 p.m. local solar time; the other satellite crosses the equator at roughly 2:00 a.m. and 2:00 p.m. local solar time.

These spacecraft monitor the entire Earth, providing atmospheric measurements of temperature, humid-ity, ozone and cloud images as they track weather patterns that affect the global weather and climate. The satellites send millions of global measurements daily to NOAA’s Command and Data Acquisition stations in Fairbanks, Alaska, and Wallops Island, Virginia, and to its data processing center in Suitland, Maryland, adding valuable information to forecasting models, especially for ocean areas, where conventional ground-based data are lacking.

Currently, NOAA has two operational polar orbiters: NOAA-14, launched in December 1994, into a 1:40 p.m. local solar time orbit and NOAA-15, launched in May 1998, into a 7:30 a.m. local solar time orbit.  NOAA-L will replace NOAA-14 in a 2:00 p.m. local solar time orbit.

NOAA-L will be renamed NOAA-16 after achieving orbit. The satellites receive a letter designation while under construction on the ground and are then renamed with a numerical designation after launch. This is done because the satellites are built in alphabetical order but are not necessarily launched in this same order. Therefore, to avoid confusion, they are numbered upon reaching orbit.

The NASA-NOAA Partnership

NASA and NOAA are actively engaged in a cooperative program to develop and launch the NOAA Polar Operational Environmental Satellites (POES).  NOAA is responsible for program requirements, funding and the on-orbit operation of the multi-satellite system. NOAA also determines the need for satellite replacement.  NOAA designs and develops the ground system needed to acquire, process and disseminate the satellite data. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is responsible for the construction, integration and verification testing of the spacecraft, instruments and unique ground equipment.  NOAA-L will be launched by the U.S. Air Force on a Titan II launch vehicle, a refurbished ballistic missile. After launch, NASA checks out the satellite to assure it meets its performance requirements. NASA turns operational control of the spacecraft over to NOAA after 10 days of comprehensive subsystem checkout. An on-orbit instrument performance verification period lasts an additional 35 days.

NOAA-L

NOAA-L, the latest in the spacecraft series, will broadcast data directly to thousands of users around the world. The spacecraft will continue providing a polar-orbiting platform to support the environmental monitoring instruments for imaging and measuring the Earth’s complex coupled systems–its atmosphere, its surface and cloud cover. Observations include information about Earth radiation, sea and land surface temperature, atmospheric vertical temperature, water vapor and ozone profiles in the troposphere and stratosphere.

Measurement of proton and electron flux at orbit altitude, remote platform data collection and the Search and Rescue Satellite-aided Tracking system (SARSAT) are also supported. NOAA-L will be the second in the series to support a new suite of dedicated microwave instruments to generate improved temperature and moisture profiles and surface and hydrological products in cloudy regions where visible and infrared instruments have decreased capability.

Spacecraft Design

The NOAA satellite series is designed for a two-year mission life, but historically, they have averaged a lifetime more than twice as long. The satellite has a three-axis body stabilized design. This enables the satellite to point accurately toward the Earth and provide continuous global images of cloud cover; surface parameters such as snow, ice and vegetation; and atmospheric temperatures, moisture and aerosol distributions.  The satellite is also able to collect and relay information from fixed and moving data platforms, such as buoys, free-floating balloons and remote weather stations.

Each satellite consists of an imaging system, the Advanced Very High Resolution Radiometer (AVHRR/3) and a sounding suite of instruments consisting of the High Resolution Infrared Radiation Sounder (HIRS/3) and the Advanced Microwave Sounding Units (AMSU-A for temperature profiles and AMSU-B for moisture profiles).

The NOAA satellites also include a Space Environment Monitor (SEM/2) that provides measurements to determine the intensity of the Earth’s radiation belts and the flux of charged particles at the satellite altitude.  The monitor warns of solar wind occurrences that may impair long-range communication or high-altitude operations, damage satellite circuits and solar panels, or change drag and magnetic torque on satellites.

Also flying on NOAA-L is the Solar Backscatter Ultraviolet Radiometer (SBUV/2). Both an imager and a sounder, the SBUV/2 produces total ozone maps and measures the ozone distribution in the atmosphere as a function of altitude.

A very important mission of these spacecraft is that of lifesaving. Each polar-orbiting NOAA satellite, except NOAA-12, is equipped with a SARSAT system, which receives emergency beacons from ships and aircraft in distress. SARSAT is part of an international satellite system for search and rescue that includes the NOAA spacecraft and the Russian-provided satellite COSPAS. The system consists of the satellites in polar orbit and an international network of Earth stations, which provide global distress alert and location information to appropriate rescue authorities for maritime, aviation and land users in distress. SARSAT has been attributed to saving more than 10,000 lives since it became operational in November 1982. Originally conceptualized and developed at Goddard in the early 1970s, this humanitarian effort is designed to reduce the time required to rescue air and maritime distress victims, thereby significantly increasing their chances for survival.

Orbit and Command

NOAA-L will operate in a circular, near-polar orbit of 470 nautical miles (870 kilometers) above the Earth with an inclination angle of approximately 98 degrees to the equator. The NOAA-L orbit period, which is the time it takes to complete one orbit of the Earth, will be approximately 102 minutes. The sunlight period will average about 72 minutes with approximately 30 minutes in the Earth’s shadow. Since the Earth rotates approximately 26 degrees during each orbit, the satellite observes a different portion of the Earth’s surface during each orbit.

The nominal orbit is Sun-synchronous and rotates eastward about the Earth’s polar axis 0.986 degrees per day, approximately the same rate and direction as the Earth’s average daily rotation about the Sun. The rotation keeps the satellite in a constant position with reference to the Sun for constant illumination throughout the year. NOAA-L will be launched so that it will cross the equator at about 2:00 p.m. northbound and 2:00 a.m. southbound local solar time.

The NOAA Satellite Operations Control Center in Suitland, Maryland, provides spacecraft scheduling, health and safety monitoring and engineering analyses. NOAA’s Command and Data Acquisition stations are located at Wallops, Virginia, and at Fairbanks, Alaska.

Data are processed in the NOAA Central Environmental Satellite Computer System and delivered to the National Weather Service’s National Centers for Environmental Prediction in Camp Springs, Maryland, and National Weather Service forecast offices across the United States.

The NOAA POES System in Weather

Forecasting

The POES spacecraft serve as complementary satellites to the geosynchronous Geostationary Operational Environmental Satellites (GOES) system.  Where the GOES satellites provide near-term data from the continental United States and Hawaii to NOAA’s forecasters, the polar-orbiting spacecraft provide full global data for short- and long-range forecast models, climate modeling and various other secondary missions.

Data Archiving and Dissemination

Data from the NOAA spacecraft are helping NASA scientists design instruments for follow-on missions for NASA’s Earth Sciences program. NOAA has the responsibility to process, analyze, disseminate and archive all operational data. These data are made available to NASA researchers and others for research and environmental applications.

More information on the POES program can be found on the Internet at:

http://www.poes.gsfc.nasa.gov

http://www2.ncdc.noaa.gov/docs/intro.htm  and

http://www.osd.noaa.gov/sats/poes.htm