Sentinels in the Sky: 50 Years of GOES Satellite Observations

Introduction

In an era where satellite observations of Earth are commonplace, it’s easy to forget that only a few decades ago, the amount of information available about the state of Earth’s environment was limited; observations were infrequent and data were sparsely located.

As far back as the late 1950s, there were primitive numerical weather prediction (NWP) models that could produce an accurate (or what a forecaster would call “skillful”) forecast given a set of initial conditions. However, the data available to provide those initial conditions at that time were limited. For example, the weather balloon network circa 1960 only covered about 10% of the troposphere and did not extend into the Southern Hemisphere, the tropics, or over the ocean.

Weather forecasters of the pre-satellite era typically relied upon manual analysis of plotted weather maps, cloud observations, and barometric pressure readings when making forecasts. They combined this limited dataset with their own experience issuing forecasts in a particular area to predict upcoming weather and storm events. While those pioneering forecasters made the most of the limited tools available to them, poor data – or simply the lack of data – inevitably led to poor forecasts, which usually weren’t accurate beyond two days. This time duration was even less than that in the Southern Hemisphere. As a result, the forecasts issued typically lacked the specificity and lead time required to adequately prepare a community before a snowstorm or hurricane.

Although the first satellite observations (e.g., from the Television Infrared Observation Satellite (TIROS) program or early Nimbus missions) whet forecasters’ appetites for what might be possible in terms of improving weather forecasting, polar orbiting satellites could only observe a given location twice a day. Those snapshots from above were insufficient for tracking rapidly evolving weather phenomena (e.g., thunderstorms, tornadoes, and intensification of hurricanes). Beyond cloud information, forecasters required data on temperature, moisture, and wind profiles in the atmosphere in addition to output from NWP models.

It was the advent of geostationary observations (also called geosynchronous) that truly led to revolutionary advances in weather forecasting. This approach enabled continuous monitoring of the atmosphere over a particular region on Earth. Hence, the development and evolution of NOAA’s Geostationary Operational Environmental Satellites (GOES) has been a major achievement for weather forecasting.

For 50 years, GOES have kept a constant vigil over the Western Hemisphere and monitored the Sun and the near-Earth environment – see Visualization 1. Since 1975, the National Oceanic and Atmospheric Administration (NOAA) and NASA have partnered to advance NOAA satellite observations from geostationary orbit. GOES satellites serve as sentinels in the sky, keeping constant watch for severe weather and environmental hazards on Earth as well as dangerous space weather. This narrative will focus on the development and evolutions of the Earth observing instruments on GOES with a mention of several of the space weather instruments.

Reaching a half-century of operation is a remarkable achievement for GOES, or any mission. The Earth Observer has published several articles chronicling the milestones of Earth observing missions, including The Vanguard of Earth-Observing Satellites [March–April 2019, 31:2, 7–18], Nimbus Celebrates Fifty Years [March–April 2015, 27:2, 18–31], and NASA Participates in Pecora 22 Symposium and Celebrates Landsat 50th Anniversary [Nov.–Dec. 2022, 34:6, 4–9]. This article, reflecting on GOES accomplishments, will join that list.

The article provides the history leading up to the development of GOES and traces the development of GOES from the earliest launch in 1975 to the last launch in late 2024, which completed the GOES–R series – see Figure 1. The article ends with a look at the plans for Geostationary Extended Observations (GeoXO), which seeks to extend the GOES legacy to the middle of the 21^st century, followed by some concluding thoughts.

GOES Heritage Missions: ATS and SMS

The heritage of GOES can be traced to the Applications Technology Satellite (ATS) series, which consisted of a set of six NASA spacecraft launched from December 7, 1966 to May 30, 1974. These missions were created to explore and flight-test new technologies and techniques for communications, meteorological, and navigation satellites. ATS was a multipurpose engineering satellite series, testing technology in communications and meteorological applications from geosynchronous orbit.

ATS satellites aimed to test the theory that gravity would anchor a satellite in a synchronous orbit, 22,300 statute miles (37,015 km) above the Earth. This orbit allowed the satellites to move at the same rate as the Earth, thus seeming to remain stationary. Although the ATS satellites were intended mainly as testbeds, they also collected and transmitted meteorological data and functioned at times as communications satellites. For example, ATS-6, the last in the series, was the first to use an education and experimental direct broadcast system, which is now commonplace on Earth observing satellites (e.g., Terra).

Also included in the ATS payload was a spin-scan camera that Verner Suomi and associates had developed in the early 1960s. The device was so named because it compensated for the motion of the satellite and still obtained clear visible (television-like) photographs. The University of Wisconsin, Madison’s (UWM) Space Science and Engineering Center (SSEC), which Suomi and colleagues at UWM had just recently established, funded the camera’s development and NASA approved its inclusion as part of the ATS payload. The spin-scan camera on ATS-1 produced spectacular full disk images of Earth; a few years later the camera on ATS-3 produced similar images, this time in color.

Although designed primarily to test and demonstrate new technologies, imagery captured by the ATS payload led to some serendipitous science. Analysis of spin-scan camera images, while labor intensive and expensive and not practical for use operationally, led to new discoveries about storm origins that had never before been available. For example, Tetsuya Fujita analyzed ATS camera images of storms in the Midwest United States in 1968 as part of his in-depth studies of tornadoes. This work led to the development of the Fujita Scale for tornado intensity. Also in 1968, “Hurricane Hunter” aircraft data and radar imagery, along with ATS images allowed meteorologists to observe the complete life cycle of Hurricane Gladys. Today, this approach is routine, but at the time it was groundbreaking.

Following the success of the ATS “technology demonstration” series, NASA and NOAA began to develop an operational prototype of the dedicated geosynchronous weather satellite, the Synchronous Meteorological Satellite (SMS). SMS-1 was launched in 1974, with SMS-2 following the next year. Owned and operated by NASA, the SMS satellites were the first operational satellites designed to sense meteorological conditions in geostationary orbit over a fixed location on the Earth’s surface. The ATS spin-scan camera manufacturers – SSEC and Santa Barbara Research – altered their ATS camera design, replacing the television-like photographic apparatus with an imaging radiometer with eight visible and three infrared channels. The revised instrument became known as the Visible and Infrared Spin-Scan Radiometer (VISSR). They also added a telescope that would allow for high-resolution imaging of smaller portions of Earth, allowing researchers to study storm formation in more detail.

First Generation: GOES 1–3

The GOES era began in October 1975 with the launch of GOES-1 (initially called SMS-3). The first three GOES missions were spin-stabilized satellites. The VISSR instrument, initially developed for the SMS missions, became the workhorse instrument for the first generation of GOES missions. VISSR provided high-quality day and night observations of cloud and surface temperatures, cloud heights, and wind fields – see Figure 2.

The early GOES missions also focused on monitoring space weather. The first generation of GOES featured a Space Environment Monitor (SEM) to measure proton, electron, and solar X-ray fluxes as well as magnetic fields around the satellites. This technology became standard on all subsequent GOES satellite missions.

The new satellites quickly began providing critical information about the location and trajectory of hurricanes. The earliest generation of GOES provided crucial data about Tropical Storm Claudette and Hurricane David in 1979 – both of which devastated regions of the United States.

Second Generation: GOES 4–7

The second generation of GOES began in 1980, with the launch of GOES-4. NASA, NOAA, and SSEC collaborated to make further enhancements to the VISSR instrument, adding temperature sounding capabilities. The development of the VISSR Atmospheric Sounder (VAS) was particularly helpful for the study and forecasting of severe storms. While there were sounders on polar orbiting satellites of this era (e.g., TIROS and Nimbus), polar orbiters, which take measurements of the same location twice daily, often missed events that occurred on shorter timescales, such as thunderstorms. By contrast, VAS on GOES could image the same area every half-hour, allowing for more detailed tracking of storms, leading to improved severe storm forecasting and enabling more advanced warning of the storm’s arrival. VAS became the basis for the establishment of an extensive severe storm research program during the 1980s.

The second generation GOES missions were capable of obtaining vertical profiles of temperature and moisture throughout the various layers of the atmosphere. This added dimension gave forecasters a more accurate picture of a storm’s extent and intensity, allowed them to monitor rapidly changing events, and helped to predict fog, frost, and freeze, as well as dust storms, flash floods, and even the likelihood of tornadoes.

The second generation of GOES helped forecasters track and forecast the impacts from the 1982–1983 El Niño event – one of the strongest El Niño–Southern Oscillation (ENSO) events on record that led to significant economic losses. This generation of GOES satellites also gave forecasters vital information about Hurricane Juan in 1985 and Hurricane Hugo in 1989, both destructive storms for areas of the United States – see Figure 3.

GOES-7, launched in 1987, added the new capability of detecting distress signals from emergency beacons. These GOES satellites have helped to rescue thousands of people as part of the Search and Rescue Satellite-Aided Tracking (SARSAT) system developed to detect and locate mariners, aviators, and other recreational users in distress. This system uses a satellite network to detect and locate distress signals from emergency beacons on aircraft and vessels and from handheld personal locator beacons (PLBs) quickly. The SARSAT transponder on GOES immediately detects distress signals from emergency beacons and relays them to ground stations. In turn, this signal is routed to a SARSAT mission control center and then sent to a rescue coordination center, which dispatches a search and rescue team to the location of the distress call.

Third Generation: GOES 8–12

In 1994, advances in two technologies enabled another significant leap forward in capabilities for GOES: improved three-axis stabilization of the spacecraft and separating the imager and sounder into two distinct instruments with separate optics (e.g., GOES Imager and GOES Sounder). Simultaneous imaging and sounding gave forecasters the ability to use multiple measurements of weather phenomena, resulting in more accurate forecasts. Another improvement was flexible scanning, where the satellites could temporarily suspend their routine scans of the hemisphere to concentrate on a small area to monitor quickly evolving events. This capability allowed meteorologists to study local weather trouble spots, improving short-term forecasts.

In 2001, forecasters used GOES-8 to track the slow-moving remnants of Tropical Storm Allison, stalled over the Gulf Coast. During the next four days, Allison dropped more than three feet of rain across portions of coastal Texas and Louisiana, causing severe flooding, particularly in the Houston area.

GOES-12, the final satellite in the third generation, launched in 2001. It included a new Solar X-ray Imager (SXI) as part of its payload. SXI was the first X-ray telescope that could take a full-disk image of the Sun, which enabled forecasters to detect solar storms and better monitor and predict space weather that could affect Earth. Some geomagnetic storms can damage satellites, disrupting communications and navigation systems, impacting power grids, and harming astronauts in space.

Fourth Generation: GOES 13–15

By the mid-2000s, the fourth generation of GOES, known as the GOES-N series, enhanced the mission with improvements to the Image Navigation and Registration subsystem, including star-trackers, to better determine the coordinates of intense storms. Improvements in batteries and power systems allowed this generation to provide continuous imaging. GOES-13 also added an Extreme Ultraviolet Sensor, which monitored ultraviolet emissions from the Sun as well as the solar impact on satellite orbit drag and radio communications.

In April 2011, GOES-13 monitored the record-breaking tornado outbreak that hit the Southeastern United States – see Visualization 2. From April 25–28, 362 tornadoes carved a path across a dozen states, leaving an estimated 321 people dead. In 2012, NOAA operated GOES-14, the on-orbit backup satellite, in a special rapid-scan test mode, providing one-minute imagery of Tropical Storm Isaac and Hurricane Sandy, both destructive storms.

The GOES-R Series: GOES-16–19

NASA launched the first satellite in the GOES-R Series for NOAA in 2016. The GOES-R Series brought new state-of-the-art instruments into orbit, including the Advanced Baseline Imager (ABI), a high-resolution imager with 16 channels, and the Geostationary Lightning Mapper, the first lightning mapper flown in geostationary orbit. The satellites also gained the ability to concurrently provide a full-disk image every ten minutes, a contiguous United States image every five minutes, and two smaller localized images every 60 seconds (or one domain every 30 seconds). For the first time, meteorologists could see the big picture while simultaneously zooming in on a specific weather event or environmental hazard.

The latest GOES satellite series brought revolutionary improvements, providing minute-by-minute information to forecasters, decision-makers, and first responders to give early warning that severe weather is forming, monitor and track the movement of storms, estimate hurricane intensity, detect turbulence, and even spot fires before they are reported on the ground.

The GOES-R Series satellites also carry a suite of sophisticated solar imaging and space weather monitoring instruments. The final satellite in the series, GOES-19, is also equipped with NOAA’s first compact coronagraph (CCOR-1). This instrument images the solar corona (the outer layer of the Sun’s atmosphere) to detect and characterize coronal mass ejections, which can disrupt Earth’s magnetosphere, leading to geomagnetic storms, auroras, and potential disruptions to technology, including electricity and satellite communications.

In 2017, Hurricane Maria knocked out Puerto Rico’s radar just before landfall. With this critical technology disabled and a major hurricane approaching, forecasters used 30-second data from GOES-16 to track the storm in real-time – see Visualization 3. The satellite’s rapid scanning rate allowed forecasters to analyze cloud patterns and understand the evolution of Maria’s position and movement as well as discern the features within the hurricane’s eye to estimate intensity.

The most recent generation of satellites also significantly improved fire detection and monitoring. During California’s Camp Fire in 2018, GOES-16 played a crucial role in monitoring the fire’s progression and smoke plumes, assisting the efforts to contain the fire – see Visualization 4. The satellite provided an extremely detailed picture of fire conditions, quick detection of hot spots, and the ability to track the fire’s progression and spread in real-time. Forecasters used ABI data from GOES-16 to track the fire’s movement and intensity even before ground crews could fully see it due to thick smoke. Not only did the data help firefighters fight the fire more effectively, but it also helped keep firefighters safe during the disaster.

What’s Next? GeoXO

NOAA, NASA, and industry partners are now developing the future generation of geostationary satellites. The Geostationary Extended Observations (GeoXO) will provide continuity of observation from geostationary orbit as the GOES-R series nears the end of its operational lifetime. The first GeoXO launch is planned for launch in the early 2030s.

GeoXO will prioritize and advance forecasting and warning of severe weather. Similar to GOES, the information GeoXO gathers will also be used to detect and monitor environmental hazards (e.g., wildfires, smoke, dust, volcanic ash, drought, and flooding).

The more advanced observing capabilities will allow forecasters to provide earlier warning to decision makers, improve the skillfulness of short-term forecasting, and allow for greater lead times for warnings of severe weather and other hazards that threaten the security and well-being of everyone in the Western Hemisphere well into the 2050s.

Conclusion

For 50 years, GOES satellites have provided the only continuous coverage of the Western Hemisphere. Their data have been the backbone of short-term forecasts and warnings of severe weather and environmental hazards. GOES detect and monitor events as they unfold, providing forecasters with real-time information to track hazards as they happen. They are also part of a global ring of satellites that contribute data to numerical weather prediction models. GOES also monitors the Sun and provides critical data for forecasts and warnings of space weather hazards.

Each successive generation of GOES has brought advancements and new capabilities that have improved the skill of short-term weather forecasts and our ability to prepare for and respond to severe weather and natural disasters. The information the satellites supply is essential for public safety, protection of property, and efficient economic activity. Meteorologists, emergency managers, first responders, local officials, aviators, mariners, researchers, and the general public depend on GOES. Everyone in the Western Hemisphere benefits from GOES data each and every day.

Acknowledgment

The primary source for the information provided in the section on “GOES Heritage Missions” was Conway, Eric: Atmospheric Science at NASA: A History (2008), pp. 140–41.

Michelle Smith
NOAA Satellite and Information Service
michelle.smith@noaa.gov

Alan Ward
NASA’s Goddard Space Flight Center/Global Science & Technology Inc.
alan.b.ward@nasa.gov