Meteorologists need sensors that are on the ground directly measuring local weather conditions, as well as in orbit high above Earth’s atmosphere observing the "big picture" remotely. The United States has a network of ground stations for measuring surface and upper-air weather conditions at particular locations and times. However, this network leaves gaps in the information about the geographical extent of weather phenomena, their speed and direction of movement, and their duration. Satellite data are also needed to provide a complete and continuous picture of atmospheric conditions. Forecasting the approach of severe storms since 1975, GOES are a cornerstone of weather observing and forecasting.
Geostationary satellites rotate with Earth from west to east directly over the equator at an altitude of 35,800 km (22,300 statute miles). Because the satellite orbits in the same direction as Earth turns on its axis and matches the speed of Earth’s rotation at the equator, the satellite always has the same view of the Earth’s surface. Geostationary satellites are in position to maintain a constant vigil over nearly half the planet.
NOAA’s forecast responsibilities cover the area from Guam to the coast of Africa – the largest being marine and aviation route forecasts. NOAA’s GOES satellites observe the Western Hemisphere on Earth from an equatorial view approximately 22,300 miles high. Because they orbit in the same direction as Earth turns on its axis and match the speed of Earth’s rotation at the equator, the satellites always have the same view of the Earth’s surface. They are positioned to view the west coast of the United States and Pacific Ocean (GOES-West) and the east coast and Atlantic Ocean (GOES-East).
Geostationary weather satellites work by sensing electromagnetic radiation to indicate the presence of clouds, water vapor, and surface features. Unlike ground-based radar systems and some other types of satellites, these satellites do not send energy waves into the atmosphere and analyze returning signals. Rather, the GOES work by passively sensing energy. The GOES sense visible (reflected sunlight) and infrared (for example, heat energy), from the Earth’s surface, clouds, and atmosphere. The Earth and atmosphere emit infrared energy 24 hours a day, and satellites can sense this energy continuously. In contrast, visible imagery is available only during daylight hours when sunlight is reflected.
The instruments on the GOES that measure electromagnetic energy are called radiometers. GOES carries two types of imagers: One measures the amount of visible light from the sun that Earth’s surface or clouds reflect back into space. The second measures the infrared energy that Earth’s surface and clouds radiate back to space. Because the GOES can sense infrared radiation, they can operate at night.
Most visible light passes right through the atmosphere, but no so much through the clouds. Clouds reflect some of the visible light back into space. How much depends upon the thickness and height of the cloud. Earth’s surface absorbs the visible light energy, gets warmer, and re-radiates the energy as infrared radiation. Clouds also absorb some of the visible light energy, as well as the infrared energy re-radiated from Earth. Satellite sensors are particularly sensitive to those wavelengths of infrared energy re-radiated up through to the atmosphere to space. Scientists can measure the height, temperature, moisture content (and more) of nearly every feature of the Earth’s atmosphere, ocean, and land surface, with and without vegetation.
Communications, transportation, and electrical power systems can be disrupted and damaged by space weather storms. Exposure to radiation can threaten astronauts and commercial air travelers alike, and has affected the evolution of life on Earth. Geomagnetic storms and other space weather phenomena pose a serious threat to all space operations, and can result in total mission failure.
Beginning with GOES-I, the Search and Rescue subsystem has been carried on each of the GOES. Distress signals are broadcast by Emergency Locator Transmitters carried on general aviation aircraft, aboard some marine vessels, and by individuals, such as hikers and climbers. A dedicated transponder on each GOES detects and relays signals to a Search and Rescue Satellite-Aided Tracking (SARSAT) ground station. GOES-R’s transponder will be able to operate at a lower uplink power than previous GOES transponders, enabling GOES-R to detect weaker beacon signals. Through a rescue coordination center, help is dispatched to the aircraft, ship, or individual in distress. SARSAT is an international program, with many satellites making up a world-wide network of emergency beacon transponders. Since 1982, SARSAT helped save more than 39,000 lives worlwide.
The GOES-R Series is the next generation of NOAA geostationary Earth-observing systems. The satellite’s advanced spacecraft and instrument technology will support expanded detection of environmental phenomena, resulting in more timely and accurate forecasts and warnings. Learn more on the Mission page of this site.
There are four satellites in the GOES-R Series Program: GOES-R, GOES-S, GOES-T and GOES-U. They are not launched at the same time; rather they are built and launched sequentially over many years. These satellites continue a more than 40 year legacy of geostationary weather satellites going back to GOES-A. Operationally, NOAA maintains two satellites on orbit, GOES-East and GOES-West, and maintains a backup satellite in a central position to ensure a robust constellation should a problem occur with an operational satellite. For example, in GOES-14, the on-orbit spare, was used to cover the GOES-East location following a GOES-13 issue and again in 2013 following a micrometeroid collision.
The total GOES-R lifecycle budget is $10.83B, of which approximately $6.1B was spent by the end of FY2015. The budget encompasses the entire life of the development and operation of the four satellites in the series (GOES-R, S, T & U), which spans more than 30 years, from 2005 to 2036. This also includes all instruments, ground segment work, antenna systems, the construction of a remote backup satellite data facility in West Virginia, new construction to the primary satellite station in Wallops Island, Va. and upgrades to the NOAA Satellite Operations Facility (NSOF) in Maryland. This budget is also used to fund the Environmental Satellite Processing and Distribution System (ESPDS) and a Comprehensive Large-Array Stewardship System (CLASS) to process and archive GOES-R data and ultimately make it available to end users.
GOES-S, which will become GOES-17 upon reaching geostationary orbit, will be operational as NOAA’s GOES West after a period of checkout and validation. GOES-17 will replace GOES-15 as the GOES West operational satellite. At 137 degrees west longitude, GOES-17 will watch over the western United States, Alaska, Hawaii, Mexico, Central America, and the Pacific Ocean all the way to Guam.
After launch, GOES-R Series satellites reach orbit approximately two weeks later. At that time, the letter designation becomes a number. For example, GOES-R became GOES-16 when it reached geostationary orbit. The satellite then travels to a checkout orbit of 89.3 degrees west where it undergoes a period of checkout and validation. During that time, it will undergo instrument outgassing (an operation that prevents contamination from collecting on the instruments’ optical surface) and on-orbit calibration tests. Once data starts to flow, instrument-level testing and product validation will begin. Once checkout and validation are complete, the satellite drifts to its operational location.
GOES-R Series advanced spacecraft and instrument technology supports expanded detection of environmental phenomena, resulting in more timely and accurate forecasts and warnings. The Advanced Baseline Imager (ABI) collects three times more data and provides four times better resolution and more than five times faster coverage than previous GOES. The GOES-R Series satellites also carry the first lightning mapper flown from geostationary orbit. The Geostationary Lightning Mapper, or GLM, detects the light emitted by lightning at the tops of clouds day and night and collects information such as the frequency, location and extent of lightning discharges. The instrument measures total lightning, both in-cloud and cloud-to-ground, to aid in forecasting developing severe storms and a wide range of high-impact environmental phenomena including hailstorms, microburst winds, tornadoes, hurricanes, flash floods, snowstorms and fires. The satellites also host a suite of instruments that provide significantly improved detection of space weather for more accurate monitoring of energetic particles responsible for radiation hazards, improved power blackout forecasts, increased warning of communications and navigation disruptions, and more.
GLM detects lightning using a high-speed camera and looks for rapid increases in light level at individual pixels compared to the slowly changing cloud scene. The GLM is sensitive to in-cloud lightning as well as cloud-to-ground lightning. This is significant as studies have indicated the total lightning activity, and the in-cloud lightning in particular, increases as storms intensify and become more likely to produce severe weather at the ground. In this way, the GLM data combined with the Advanced Baseline Imager and weather radar are expected to increase forecaster situational awareness resulting in greater warning lead-time for the public. The ground-based lightning networks detect cloud-to-ground lightning with high accuracy, but are less sensitive to the in-cloud lightning. Forecasters intend to combine the total lightning from GLM with ground-based lightning data to build a complete overall description of the lightning activity.
In general, visible imagery is mainly used in the identification of clouds. Visible images are frequently used for weather forecasting but are only available during the daytime. Infrared imagery is available 24 hours a day because it monitors emitted radiation. Each band has many uses, for example the visible and near-IR bands are used for monitoring aerosols, clouds, hurricanes, snow cover, and atmospheric motion, while the IR bands monitor aerosols, clouds, hurricanes, rainfall, moisture, atmospheric motion and volcanic ash. The GOES-R Series Advanced Baseline Imager has 16 bands, including two visible channels, four near-infrared channels, and ten infrared channels. The ABI Technical Summary provides information on what each of the 16 bands is used for.
The ability to observe targeted areas of severe weather every 30-60 seconds allows forecasters to see what is happening in near real-time and provide information not captured in previous satellite imagery, such as the formation and evolution of rapidly-developing severe weather. This enables more advanced warnings and effective evacuations.
GOES satellites see the entire Western Hemisphere, not just the United States. There are a number of ways that other countries in the Western Hemisphere are able to access GOES-R Series data. GOES Rebroadcast (GRB) is the primary space relay of full resolution, near real-time direct broadcast data. These data are available to all users with GRB receivers in view of a GOES-R Series satellite at the East or West operational longitudes. The Product Distribution and Access (PDA) system receives and store real time environmental satellite data and makes them available to authorized users. The Comprehensive Large Array-data Stewardship System (CLASS) is a web-based data archive and distribution system for NOAA’s environmental satellite data. Users in North, Central and South America (including the Caribbean Basin) are also able to access data through GEONETCast-Americas (GNC-A), which disseminates near real time data through relatively inexpensive satellite receiver stations.
The early GOES (A-C) satellites were spin-stabilized, viewing Earth only about ten percent of the time and provided data in only two dimensions. There was no indication of cloud thickness, moisture content, temperature variation with altitude, or any other information in the vertical dimension. In the 1980s the capability was added to obtain vertical profiles of temperature and moisture throughout the atmosphere. This added dimension gave forecasters a more accurate picture of the intensity and extent of storms, allowed them to monitor rapidly changing events, and to predict fog, frost and freeze, dust storms, flash floods, and even the likelihood of tornadoes. However, as in the 70s, the imager and sounder still shared the same optics system, which meant the instruments had to take turns. Also, the satellites were still spin-stabilized. GOES-I, launched in 1994, brought real improvement in the resolution, quantity, and continuity of the data. Advances in two technologies were responsible: three-axis stabilization of the spacecraft and separate optics for imaging and sounding. Three-axis stabilization meant that the imager and sounder could work simultaneously. Forecasters had much more accurate data with which to better pinpoint locations of storms and potentially dangerous weather events such as lightning and tornadoes. The satellites could temporarily suspend their routine scans of the hemisphere to concentrate on a small area of quickly evolving events to improve short-term weather forecasts. GOES-N, O, and P further improved the imager and sounder resolution with the Image Navigation and Registration subsystem, which uses geographic landmarks and star locations to better pinpoint the coordinates of intense storms. Detector optics were improved and because of better batteries and more available power, imaging is continuous.
The GOES-R Series marks the first major technological advances in geostationary observations since 1994. The GOES-R series (GOES R, S, T and U) imager has three times the spectral channels, 4 times the resolution and 5 times faster coverage than previous GOES, allowing for the “nowcasting” of severe storms. GOES-16 flies the first operational lightning mapper flown in geostationary orbit, which measures total lightning, both in-cloud and cloud-to-ground, to aid in forecasting developing severe storms and a wide range of high-impact environmental phenomena including hailstorms, microburst winds, tornadoes, hurricanes, flash floods, snowstorms and fires. The GOES-R Series satellites also offer improved monitoring of solar activity and earlier warnings of hazardous space weather.
The GOES-R ground system is located in two primary locations: the NOAA Satellite Operations Facility (NSOF) in Suitland, Maryland and the Wallops Command Data Acquisition Center (WCDAS) at Wallops, Virginia. A third operations facility in Fairmont, West Virginia, will serve as a backup location in the event of a communications issue at either NSOF or WCDAS. Additional information is available in the ground system overview of this site.
The GOES-R Series Program is engaging users early in the process through Proving Ground and NOAA testbed activities, simulated data sets, scientific and user conferences, and other communication and outreach efforts. » Learn more about user readiness efforts here.
The Proving Ground is a collaborative effort between the GOES-R Program Office, NOAA Cooperative Institutes, a NASA center, NWS Weather Forecast Offices, NCEP National Centers, and NOAA testbeds across the country. The Proving Ground is a project in which simulated GOES-R products can be tested and evaluated before the GOES-R satellite is launched. The simulated GOES-R products are generated using combinations of currently available GOES data, data provided by instruments on polar-orbiting satellites, and model synthetic satellite data. Additional information is available in the Proving Ground section of this site.
: GOES Rebroadcast is the primary space relay of Level 1b products from GOES-R Series satellites and replaces the GOES VARiable (GVAR) service. GRB provides full resolution, calibrated, navigated, near-real-time direct broadcast data. » Learn more about GRB.
Users must either acquire new systems to receive GRB or upgrade components of their existing GVAR systems. At a minimum, GVAR systems will require new receive antenna hardware, signal demodulation hardware, and computer hardware/software system resources to ingest the extended magnitude of GOES-R GRB data. See the GRB Downlink Specifications and GRB Product Users Guide (PUG) documents for more information.
The GRB Simulators allow for on-site testing of user ingest and data handling systems, aka GRB field terminal sites. Each unit simulates GRB downlink functionality by generating Consultative Committee for Space Data Systems (CCSDS) formatted GRB output data based on user-defined scenarios, test patterns, and proxy data files. Four GRB simulators have been designated for loan to borrowers who manufacture GRB receivers and other users interested in testing their receive systems. The objective is to allow borrower access to simulators to verify GRB receive system compatibility with the GRB transmission. Information about requesting a simulator for loan can be found at http://go.usa.gov/WvXY. For a complete list of frequently asked questions about the GRB Simulator, see the GRB Simulator FAQs document.