With today's advanced technology, it may be difficult to remember the days when there were no weather satellites, but it was less than a half century ago that many areas had little or no advance severe weather warning. Fortunately, modern NOAA satellites can spot and accurately track severe storms while they are still more than half a continent away.

NOAA’s Modern Satellite Capabilities
Since then, many NOAA weather satellites have been launched into orbit and their capabilities have improved significantly with new technologies. Not only do modern NOAA satellites observe clouds to track potentially devastating storms, but they also carry many instruments used to measure various environmental variables — providing vital information to not only meteorologists, but farmers, geologists, fishermen, foresters, the military, transportation sector and others. Perhaps most importantly, satellites are a vital component in the creation of a global earth observing system.

Click NOAA image for a larger view of poster depicting the climatological capabilities of NOAA's polar-orbiting satellites. Click here for high resolution version. Please credit “NOAA.”

• Atmospheric information about vertical moisture and temperature profiles, cloud properties, the Earth’s radiation budget, precipitation and brightness temperature (a measure of the intensity of radiation thermally emitted by an object)
• Land-based surface temperatures, as well as snow and ice cover
• Sea surface temperatures
• Opportunistic imagery from dust storms, fire/smoke, flooding, severe weather, tropical and volcanic events
• Other information from surface-based platforms (i.e., instrumented buoys, river gauges, automatic weather stations, seismic and tsunami stations and ships), space environmental monitoring and search and rescue satellite-aided tracking systems (also known as COSPAS-SARSAT) in support of humanitarian rescue operations.

Some environmental variables, however, are measured by only one particular type of NOAA satellite system. GOES, for example, can measure winds and the overall stability of the atmosphere. POES, on the other hand, can provide information about aerosols and ozone levels in the atmosphere, land surface emissivity and vegetation on land, sea ice and even oil spill events.

Image credit: NOAA

NOAA SATELLITES
Today, the nation's environmental satellites are operated by the NOAA Satellite and Information Service in Suitland, Md. The NOAA satellite system is composed of two types of satellites: GOES for national, regional, short-range warning and "now-casting" and POES for global, climate forecasting and environmental monitoring. Both types of satellites are necessary for providing a complete global weather monitoring system.

In addition, NOAA operates satellites in the Defense Meteorological Satellite Program, which are polar-orbiting satellites once owned by the U.S. Department of Defense’s Air Force Space and Missile Systems Center. In 1998, President Clinton combined the functions of the DMSP satellites with that of NOAA's POES satellites, in order to create a more cost effective and higher performance integrated system. Later this decade, these satellites will be replaced by NOAA's next generation of polar satellites (i.e., the National Polar-Orbiting Operational Environmental Satellite System).

The NOAA Satelllite and Information Service also manages the processing and distribution of the millions of bits of data and images the satellites produce each day. Specifically, NOAA satellites send more than 16,000 global measurements daily to the NOAA Environmental Satellite Processing Center computers, adding valuable information to weather forecasting and climate models, especially for remote ocean areas where conventional data are lacking. The prime customer is the NOAA National Weather Service, which uses satellite data to create forecasts for television, radio and weather advisory and warning services. Satellite information is also shared with various Federal agencies, such as the U.S. Departments of Agriculture, Interior, Defense and Transportation; with other countries, such as Japan, India and Russia; members of the European Space Agency and the United Kingdom Meteorological Office; and the private sector.

NOAA’s Geostationary Operational Environmental Satellites
GOES provide the kind of continuous monitoring necessary for intensive data analysis. They circle the Earth in a geosynchronous orbit, traveling at an altitude of 22,300 miles (35,800 km) above the Earth's equatorial plane at a speed matching the Earth's rotation.

Because they both stay at a fixed spot on and provide a complete view of the Earth's surface, GOES are ideal for monitoring large-scale environmental phenomena (i.e., meteorology, hydrology and oceanography). For example, GOES can constantly monitor for atmospheric "triggers" for severe weather conditions, such as tornadoes, flash floods, hail storms and hurricanes. When these conditions develop, the GOES satellites can monitor storms and track their movements in near real time.

Most satellite images seen on the nation’s broadcast media and The Weather Channel are produced by GOES satellites. Usually, the infrared images are "animated" to show the progression and movement of storms.

The data gathered by the GOES satellites, combined with that from new Doppler radars and sophisticated communications systems have made for improved forecasts and weather warnings that save lives, protect property and benefit agricultural and a variety of commercial interests.

The United States normally operates two meteorological satellites in geostationary orbit over the equator. Each satellite views almost a third of the Earth's surface: one monitors North and South America and most of the Atlantic Ocean, the other most of the Pacific Ocean basin, including Alaska and Hawaii.

NOAA's geostationary weather satellites trace their roots to NASA's Applications Technology Satellite (ATS), launched in December 1966, while the first GOES was launched on Oct. 16, 1975. It formed part of a two-satellite constellation that viewed nearly 60 percent of the Earth's surface (Unfortunately, GOES can only provide a very distorted view of the poles).

Currently Operating GOES
Currently, the United States is operating GOES-10 and GOES-12. (GOES-9, which is partially operational, is being used by the Japanese Meteorological Agency over the West Pacific Ocean. JMA launched MTSAT-1R in February 2005, which is expected to replace the aging GOES-9 in mid-summer 2005. GOES-11 is being stored in orbit as a replacement for GOES-12 or GOES-10 in the event of failure. GOES-12 (or GOES-East) is positioned at 75 W longitude and the equator, while GOES-10 (or GOES-West) is positioned at 135 W longitude and the equator. The two operate together to produce a full-face picture of the Earth — both day and night.

The Future of the GOES Satellite Program
The recent procurement of the GOES-N through -Q spacecraft marks the extension of the multi-satellite program designed to provide continuous monitoring of the Earth’s weather systems and the related space environment. The new spacecraft will be used to continue and enhance the functions of the current GOES series of spacecraft. The next GOES satellite, GOES-N, will be launched later this year.

NOAA’s Polar-Orbiting Satellites
Complementing the geostationary satellites are two polar orbiting satellites. Constantly circling the Earth in sun-synchronous orbit, these satellites support large-scale, long-range forecasts and numerous secondary missions. The global data from these satellites are used extensively in NOAA's weather and climate prediction numerical models.

The satellites circle the Earth in an almost north-south orbit, passing close to both poles. As the Earth rotates to the east beneath the satellite, each pass monitors an area to the west of the previous pass. These "strips" can be pieced together to produce a picture of a larger area. POES also circle at a much lower altitude (about 530 miles or 850 km) compared to GOES, providing more detailed information about the atmosphere. Operating as a pair, these satellites ensure that data for any region of the Earth are no more than six hours old. One crosses the equator at 7:30 a.m. local time, the other at 1:40 p.m. local time.

Currently Operating POES
Today's polar-orbiting weather satellites trace their roots to the Television Infrared Observation Satellite (also known as TIROS), launched in 1960.

NOAA poster depicting the capabilities of NOAA's polar-orbiting satellites to detect various hazards. Image credit: NOAA

The Future of the POES Satellite Program
A new NOAA polar-orbiting environmental satellite, NOAA-N was launched on May 20, 2005, will be critical in the continued development of a global Earth observation program, while improving the agency's weather and climate forecasts and U.S. search and rescue operations.

"NOAA-N is key to achieving the goals of a strong Global Earth Observation System of Systems," said retired Navy Vice Admiral Conrad C. Lautenbacher, Jr., Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. "Because it will strengthen our understanding about what the environment around the world is doing, not just here in the U.S., NOAA-N will bring us one step closer to truly global coverage of Earth's complex processes."

Initial Joint Polar-Orbiting Operational Satellite System
The launch of NOAA-N will also start a new era of international cooperation. Under an agreement between NOAA and the European Organization for the Exploitation of Meteorological Satellites, NOAA will provide NOAA-N and a later satellite, NOAA-N Prime, for an afternoon orbit of the globe, carrying an EUMETSAT instrument. In return, EUMETSAT will provide and launch three European-built satellites, called Metop, into morning orbits during the next 10 years, carrying key NOAA instruments. The first Metop launch is scheduled for April 2006. The cooperative agreement created what is now known as the Initial Joint Polar-Orbiting Operational Satellite System.

depicting the oceanic capabilities of NOAA's polar-orbiting satellites.  Source: NOAA

Relevant Web Sites

• NOAA Satellite and Information Service
• NOAA Satellites
• NOAA's Geostationary and Polar-Orbiting Weather Satellites
• NOAA HIGHLIGHTS DETAILS OF NEW POLAR-ORBITING SATELLITE: Launch Kicks Off New Era of International Cooperation