Why Are Earth-Observing Satellites So Important?

Satellite floating in space


Earth got its first artificial satellite 60 years ago, when the 1957 launch of a beeping ball named Sputnik kicked off the Space Age. Thousands of other, fancier satellites have followed since, and about 1,400 are operational today, including a variety of cool scientific tools like space telescopes. Yet while these science satellites often focus outward, using their height for a better view of the universe, Earth's orbit also offers a vital view of something else: Earth itself.

Earth-observing satellites now play many important, even life-saving roles around the world, and some of the most powerful are managed by two U.S. agencies: the National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA). These satellites perform some well-known services, like helping us predict and track dangerous storms, but also provide a wide range of lesser-known benefits. And given recent reports of potentially dramatic budget cuts for NOAA's satellite division — along with similar concerns about NASA's Earth Observatory — maybe those benefits are a little too lesser-known.

To shed more light on why U.S. Earth-observing satellites are so valuable, and why we need so many of them, here's a closer look at some of the satellites and what they actually do.

Anticipating tornadoes

Photo: NOAA

Earth-observing satellites are critical tools for forecasting all kinds of severe weather events. NOAA's satellites provide an especially valuable stream of information, constantly imaging storms and cloud cover, measuring surface temperatures and monitoring precipitation, among many other tasks.

"This 24/7, uninterrupted flow of essential environmental intelligence is the backbone of the National Weather Service's sophisticated computer modeling to create forecasts and warnings for severe weather events," NOAA explains, "thereby saving lives and protecting local communities."

Tornadoes, for example, are complex phenomena that can be difficult to predict, so we need a variety of data to inform our models and forecasts. That includes information from aircraft and surface sensors, but satellites can offer uniquely valuable data about severe thunderstorms — and any tornadoes they may spawn. These data are fed into sophisticated computer models that can calculate the atmosphere's likely next moves, and also provide more direct details about factors like moisture-channel variations and cloud rotation that can improve tornado forecasts.

Different satellites carry different kinds of instruments, and their various data can be synthesized to create a fuller picture than any single satellite could offer on its own. And new technology is making NOAA's satellite fleet even more valuable — the GOES-16 satellite was added in late 2016, part of the Geostationary Operational Environmental Satellite (GOES) system, and is already a "game changer," the agency says. It can scan the Western Hemisphere every 15 minutes, the continental U.S. every 5 minutes, and areas of severe weather every 30 to 60 seconds, all at the same time. It offers more spectral bands with higher resolution and faster speed than ever before, and among other benefits, provides increased warning times for thunderstorms and tornadoes.

Enlightening about lightning

Photo: NASA

One impressive tool in GOES-16's arsenal is its Geostationary Lightning Mapper (GLM), the planet's first lightning detector in a geostationary orbit. The GLM continually looks for lightning flashes across the Western Hemisphere, providing data that can tell forecasters when a storm is forming, intensifying and becoming more dangerous. "Rapid increases of lightning are a signal that a storm is strengthening quickly and could produce severe weather," NOAA explains, so this kind of insight offers another crucial clue about the development of dangerous storms.

GLM data can also reveal when a storm has stalled in place, and along with factors like precipitation, soil moisture and topography, this can help forecasters issue earlier flood warnings. In dry areas like the U.S. West, the GLM is also useful for anticipating when and where lightning might lead to wildfires. And it's not just a proxy for larger problems, since lightning itself is a direct danger to human life. The GLM is designed to detect in-cloud lightning, too, which often occurs 10 minutes or more before potentially deadly cloud-to-ground strikes. "This means more precious time for forecasters to alert those involved in outdoor activities of the developing threat," NOAA notes.

Forecasting hurricanes

Photo: NASA/NOAA GOES Project

In 1943, the Texas coast was devastated by a "surprise hurricane" no one saw coming. There were no weather satellites in 1943 — the first wouldn't enter orbit for another 20 years — and not even weather radar was available yet. Plus, ships' radio signals had been silenced in the Gulf of Mexico due to U.S. concerns about German U-boats, further curbing the chances for adequate warning.

Today, however, no hurricane can get very far without hordes of humans watching its every move. We have several ways of tracking and predicting what tropical cyclones do, but as with many storms, NOAA and NASA satellites are some of our best bets for understanding them.

Both agencies have several satellites up to this task. NOAA's GOES system provides precise data and imagery of hurricanes, like the 2015 GOES-West image above, while NASA's Terra satellite — the flagship of its Earth-observing fleet — carries a suite of instruments that have made it a key part of humanity's defense against hurricanes. And aside from all these eyes in the sky, NASA also recently launched eight micro-satellites, known as the Cyclone Global Navigation Satellite System (CYGNSS), to improve our understanding of hurricane formation. "The mission will study the relationship between ocean surface properties, moist atmospheric thermodynamics, radiation and convective dynamics to determine how a tropical cyclone forms and whether or not it will strengthen, and if so by how much," explains the University of Michigan's Space Physics Research Laboratory, which helped develop the system. "This will advance forecasting and tracking methods."

Here's an example of what one NASA satellite, the Global Precipitation Measurement (GPM) Core Observatory, revealed as Hurricane Matthew approached U.S. shores in early October 2016:

Monitoring fires and floods

Photo: NASA

As climate change spurs more extreme weather patterns, the threat of droughts — and thus wildfires — is growing for many parts of the U.S. That's notoriously true in drier Western states, but there's also plenty of fire potential farther east, as people in the Southeastern U.S. were reminded in 2016. Natural wildfires shouldn't always be fully fought, but whether we're extinguishing or just containing a fire, Earth-observing satellites provide life-saving perspective.

NOAA and NASA satellites can track fire risk by measuring things like precipitation, soil moisture and vegetation health, helping reveal the need for prescribed burns or other precautions to avoid an out-of-control wildfire. They also help monitor the size and movements of fires by spying on their smoke, which can pose an additional public-health threat far beyond the fire itself.

On the other end of the spectrum, Earth-observing satellites can also help us stay ahead of floodwaters, including those caused by ice jams. Ice-jam floods are common along some rivers in winter and spring, and by tracking the location and motion of river ice via satellites, officials can issue earlier flood warnings. Satellites also play a vital role in predicting flash floods, especially in sparsely populated rural areas with few other sources of rainfall data, like gauges or radar.

Informing farmers

Photo: NOAA

Weather and climate data are especially valuable for farmers and livestock producers, whose livelihoods may depend on having time to prepare for a downpour, a deep freeze or a drought. NOAA works with the U.S. Department of Agriculture (USDA) to help them stay informed, and the two agencies formalized this partnership in 1978 via the Joint Agricultural Weather Facility (JAWF), whose mission is to keep U.S. growers, exporters, commodity analysts and USDA staff informed of worldwide weather developments and their potential effects on crops and livestock.

To achieve that goal, experts at NOAA and the USDA analyze weather data from satellites and other sources, assess how that weather will affect agricultural production, and then publish their findings in the Weekly Weather and Crop Bulletin (WWCB), a publication that dates back to the 1890s. Described as "part weather report and part crop forecast," the WWCB offers state-by-state weather stats, international weather reports, global crop-production summaries, imagery from geostationary satellites and various "blended" data products from multiple data sources. Beyond the WWCB, NOAA and the USDA also collaborate on projects like Crop Explorer, a web-based application offering "near real-time agro-meteorological information" and other data products.

And while NOAA's focus is on American farmers, satellites also provide a broader view. That's useful in weather prediction, since weather patterns often begin outside U.S. borders, and it can also be a boon for U.S. growers whose crops must compete in global markets.

"[The Weekly Weather and Crop Bulletin] helps farmers keep up with the world commodity picture," USDA deputy chief meteorologist Mark Brusberg explained in a 2016 statement. "Our farmers are interested in what's going on in Europe and South America because it ultimately impacts what they would grow and what their prices might be."

Tracking climate change

Photo: NOAA

On top of all the localized, short-term benefits we get from Earth-observing satellites, one of their most important missions is to reveal a much bigger picture: our increasingly erratic climate, both in the U.S. and worldwide. NOAA and NASA satellites would be important windows on natural climate changes even without human interference, but given the worldwide crises caused by our species' greenhouse-gas emissions, their big-picture view is particularly urgent.

And as NASA scientist Eric Fetzer noted in 2015, the key to seeing that big picture is to amass lots of precise environmental data over time and space, a task that would suffer dramatically without satellites. "The big goal is to gauge how the atmosphere responds to changes," Fetzer said, "and to fully understand the long-term trends, you'd better understand the short-term trends really well."

Satellites are crucial tools for understanding climate change, providing too many different insights to adequately describe here. All weather data become climate data over time, so anything we learn about the short-term behavior of tornadoes, hurricanes, El Niño or the Arctic Oscillation can inform our longer-term grasp of how climates are changing. And satellites also relay critical data about remote places like the Arctic Ocean, Greenland and Antarctica, where melting glaciers and sea ice have major implications for people around the world. That includes rising sea levels, for example, which we'd know much less about if not for satellites working tirelessly overhead.

Studying threats to public health

Photo: NASA Earth Observatory

Earth-observing satellites already shed light on public-health risks related to severe weather, and on those stemming from climatic changes like sea-level rise, droughts and food shortages. But they also offer insight about other, less obvious risks like harmful algal blooms (HABs), which can occur naturally or due to fertilizers in stormwater runoff, which overfeed toxin-producing algae until they form big, dangerous "blooms." HABs can occur in seawater or freshwater, and periodically plague water bodies with dense human populations nearby, like Lake Erie or Florida's Lake Okeechobee.

HABs can sicken people and wildlife with their toxins — or indirectly create low-oxygen "dead zones" that kill aquatic life — and they cause an estimated $82 million in U.S. economic losses per year. Imagery from both NOAA and NASA satellites are used to assess and forecast HABs, helping officials determine the size and location of a bloom, where it's headed, whether it features a toxic algae species and if it might grow more severe in the near future.

Even some infectious diseases can be tracked by satellites. The spread of mosquito-born illnesses like malaria, for example, tends to hinge on environmental factors like rainfall, temperature, humidity and plant cover, since those factors affect the life spans and breeding success of mosquitoes. "I don't see mosquitoes from satellites, unfortunately, but I see the environment where mosquitoes are," NOAA scientist Felix Kogan explained in a 2015 article. "Mosquitoes like warm and moist environments and this is what I see from the operational satellites."

Since vegetated areas absorb more visible light and reflect more near-infrared light back into space, Kogan and his colleagues can use satellite-based radiation-detecting imagers to measure changes in plant cover over time. If conditions are favorable for mosquitoes, they can predict when, where and how long the malaria risk will be — one to two months in advance.

Assisting with rescues

Photo: NOAA

Aside from their many insights about severe weather, climate change and other life-and-death issues, Earth-observing satellites also help rescue people from immediately life-threatening situations. NOAA satellites are part of the international Search and Rescue Satellite-Aided Tracking System, COSPAS-SARSAT, which uses a network of spacecraft to quickly detect and locate distress signals from emergency beacons on aircraft, boats or handheld personal locator beacons (PLBs).

When a NOAA satellite pinpoints a distress signal, the location data are relayed to the SARSAT Mission Control Center at NOAA's Satellite Operations Facility in Maryland. From there, the information is quickly sent to a Rescue Coordination Center, operated by either the U.S. Air Force for land rescues, or the U.S. Coast Guard for water rescues.

In 2016, this process was used to rescue 307 people across the country, the highest total since 2007, when 353 people were saved. Two-thirds of those were water rescues, according to NOAA, while about 7 percent were aviation-related and 25 percent were land-based rescues involving PLBs.

"On any given day, at any given time," NOAA SARSAT manager Chris O'Connors said in a recent statement, "NOAA satellites can play a direct role in saving lives."

Why so many satellites?

Photo: NOAA

It may be hard to dismiss the value of Earth-observing satellites in general, but some critics say we just have too many of them. U.S. Rep. Lamar Smith (R-Texas), for one, has suggested NASA should ignore Earth science in favor of outer space, arguing "there are another dozen agencies that study earth science and climate change." Yet the other federal agency with a fleet of Earth-science satellites, NOAA, also faces the specter of potentially severe cuts to its satellite budget, raising concerns about debilitating vision loss from our life-saving eyes in the sky.

Of NASA's $19 billion budget, about $2 billion goes to its Earth-science program, while NOAA's entire budget is a relatively meager $5.8 billion. (The overall federal budget, for comparison, is more than $3 trillion.) Yet abandoning these investments could have dire consequences, from lost warning time about severe weather to lost perspective about the pace of climate change.

While it may seem redundant to have multiple agencies managing dozens of Earth-observing satellites, it's worth noting that different satellites carry different kinds of instruments to measure a wide range of Earthly signals. And even when their efforts do overlap, it's also worth noting that redundancy is rarely wasteful in science. Information from one satellite may be useful, but if that information can be corroborated by other satellites, its value skyrockets.

This list only covers a few perks of Earth-observing satellites. They also help us predict geomagnetic storms, track oil spills and plan trade routes, for example, among many other things. And while our interest in leaving Earth may be driven largely by the allure of space, these orbital lookouts embody an important lesson of the Space Age: There's no place like home (at least not anywhere nearby).