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We can’t see them, but they’ve faithfully circled above us for 50 years. From hundreds of miles away, Landsat satellites have revealed details and secrets of the Earth’s land that we miss standing on its very surface. They provide information to help us help ourselves, as we fight the risk of threats such as heat waves and wildfires and strive to manage resources like diminishing water supplies.

After the launch of the first experimental Landsat satellite in July 1972, scientists and researchers around the world marveled at what they could see in images produced from the satellite data and distributed from the USGS Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota. But more than that, they and their EROS colleagues began to apply what they learned to the puzzles and problems faced by our planet—and its inhabitants.

Video Transcript
Satellite Earth observation was an idea that worked when the first Landsat launched and still works today.

Today, the joint USGS-NASA program’s satellites Landsat 8, launched in 2013, and Landsat 9, launched in 2021, orbit the Earth opposite each other, together capturing images of each part of the land surface every 8 days. They carry on the legacy of their predecessors, with enhanced sensor technology that captures more visible and invisible wavelengths of light that can be combined to create meaningful digital images.

Landsat 8 and Landsat 9 add to the unrivaled free archive available from EROS. This archive is treasured for its consistency, reliability, and capacity to explore changes in the past that can help us plan for a better future.

Similar to global positioning system and weather data, everyone’s life has somehow been touched by Landsat.

Our Health

It might seem unlikely that a satellite 438 miles away could do anything to keep us from experiencing a medical emergency. Fortunately, users are harnessing Landsat data to do just that.

For this episode of Eyes on Earth, we hear about how a mapping project involving Landsat data helped the New York City Council identify urban heat islands.

Parts of cities containing sparse green spaces and a wealth of impervious surfaces—think roads, parking lots, and rooftops—tend to be warmer than surrounding areas. This can exacerbate the effects of heat waves and cause illness, or even death, among vulnerable residents. To counteract this in a world of warming temperatures, some cities have worked to identify these hot spots, also called urban heat islands, and implement measures to reduce their effects. Landsat 8 and Landsat 9 have improved thermal sensors that provide land surface temperature data to help cities map their urban heat islands, along with vegetation data to spot current green spaces and help strategically plan new ones.

EROS Research Scientist George Xian has taken advantage of a Landsat product developed at EROS that makes the analysis of years of data easier and more streamlined for users. He applies the land surface temperature product to his urban heat island research. “As time goes by, we’re going to see the higher and higher temperatures in the urban areas,” Xian said. “As more people are moving to the city areas, this becomes a huge impact to human health. Ecosystem health issues also are associated with urban heat.”

USGS Landsat 8 image showing algal bloom in Lake Erie in September of 2017
USGS Landsat 8 image showing algal bloom in Lake Erie in September of 2017. Landsat’s spectral bands allow researchers to see photosynthetic activity that is invisible to the naked eye.

A day at the lake can also carry health concerns. If you happen to go swimming during an undetected harmful algal bloom, you could suffer some dire effects. Animals, too, are at risk if they drink contaminated water. Landsat and other satellites offer monitoring agencies a way to help detect harmful algal blooms more easily and quickly than traditional water sampling and reports of symptoms from lake visitors. Landsat can also help keep an eye on pollutants that may contribute to blooms by monitoring watershed landscapes, land use, and runoff.

Our Water

We dig wells, build canals and dams, and install pipelines. Ultimately, however, we don’t have as much control over the water supply as we would like—and the two-decade drought in the western United States makes that clear as rivers dwindle and reservoir levels sink to historic lows. Landsat observes these changes, along with contrasting conditions such as dangerously increasing floodwaters or expanding but unstable glacial lakes.

Video Transcript
USGS Hydrologist Molly Maupin and USGS Research Physical Scientist Gabriel Senay discuss how Landsat imagery has been used by the National Water Census and in studying water use trends.

Water is needed for a variety of uses, including hydroelectric power, municipalities, and industry. In the West, however, the predominant use of water is irrigation for agriculture. One challenge for resource planners and regulators is to determine how much water irrigation uses—and how much of that water is actually absorbed by crops. Landsat can measure water use efficiency down to the field level through its capture of land surface temperature. Cooler temperatures indicate the evapotranspiration—or evaporation from soil and transpiration from leaves—of irrigated fields. This knowledge helps irrigators be more precise with their water use to avoid waste. Conserving water there can help keep our faucets and electricity flowing elsewhere.

“For over a decade, EROS pursued active research to develop and improve methods to quantify landscape water use using satellite and weather datasets,” said USGS Research Physical Scientist Gabriel Senay, who developed an evapotranspiration model based on Landsat data and works to continually improve it. “Water management starts with the water, and EROS’ ongoing effort contributes to the national goal of understanding and quantifying the water budget on a daily basis."

Our Food

One of the earliest and most critical uses of Landsat data was to monitor crops—not just in the United States but globally. Farmers, agricultural businesses, and agencies such as the U.S. Department of Agriculture (USDA) and the U.S. Agency for International Development (USAID) have a deep interest in monitoring crop types and yield, along with the growing conditions of crops and grazing land. This food-supply information can ultimately help grocery stores and restaurants anticipate availability and prices for produce and products. This directly affects what we choose to feed our families at each meal.

 For this episode of Eyes on Earth, we hear about the latest release, NLCD 2019, the importance of land cover, and how mapping teams at EROS work together to produce accurate, reliable information.

The National Land Cover Database (NLCD), the definitive land cover database for the United States, is generated at EROS in cooperation with other federal agencies. It reveals 16 types of land cover, from urban developed areas and grasslands to forests and cropland. Importantly, a comparison of different years can reveal where cropland has been lost to developed areas or expanding water bodies, or where grasslands or woodlands have converted to cropland.

NLCD is partnered with the USDA and the National Agricultural Statistics Service (NASS), among others. NASS is the agency responsible for providing upcoming crop estimates for the United States. “Using this partnership, NLCD gets very accurate training data for crop types. This provides the basis for a very accurate classification that NLCD uses to show crop conversion and crops returning to grasslands and forest. This partnership provides the best for both agencies: detailed crop types and statistics for NASS, and accurate change information for the nation from NLCD,” said USGS Physical Scientist Jon Dewitz, the technical and production manager for NLCD. 

Our Forests

Landsat has proven incredibly useful for monitoring the wide-scale loss of forests in places like the Amazon, where land may be cleared of trees legally or illegally for logging and agriculture. The resulting erosion, flooding, and even changes in weather directly affect people living nearby. Deforestation also reduces habitat for a variety of species and decreases the global capacity for carbon absorption. Satellite monitoring can help local authorities stop illegal activities.

On this episode of Eyes on Earth, we hear about the use of Landsat to study how outbreaks of native bark beetles can lead to conspicuous changes in a forest landscape. 

Closer to our own backyards, native and invasive insect infestations can be monitored on a broad scale and in remote areas by Landsat, which can detect leaf losses. This knowledge can help forest managers target treatments and track where weakened trees may endanger the public in campgrounds, other recreational areas, or next to roads.

Landsat’s archive can also help researchers understand the long-term effects and patterns of outbreaks and other forest disturbances such as wildfire and timber harvesting, along with the recovery of forests. The actual amount of forest in the United States isn’t changing a lot, said USGS Research Geographer Roger Auch at EROS, who has studied U.S. land change for more than 20 years. So, it seems paradoxical to say that forests represent the most common changes in land cover.

In reality, Landsat reveals that “timber harvesting is typically the most common disturbance event,” Auch said. But at the same time, trees begin growing elsewhere, he added. “Forest regrowth happens through both active and passive afforestation, sometimes at a rapid pace, such as industrial pine plantations in the Southeast.”

Our Homes

Landsat 8 after image of the Camp Fire in California – a 2018 wildfire.
Landsat 8 after image of the Camp Fire in California – a 2018 wildfire.

Nature can entice us to live in areas of scenic beauty and pleasant climates. But sometimes nature can threaten our homes in these very same places. A mountain cabin seems idyllic until a forest fire rages nearby. An oceanside cottage offers serenity until a storm surge swamps the neighborhood. Landsat can’t stop the forces of nature, but it can reveal the changes caused by them—and even help predict those changes to potentially alter outcomes.

On the oceans’ coasts, Landsat offers a clear view of shifting shorelines and has been used to study everything from hurricane effects and recovery to the health of salt marshes that act as storm buffers for coastal cities and their residents.

LANDFIRE, a program based at EROS involving multiple agencies, offers fire behavior modeling information based on Landsat data about vegetation and land disturbances. Firefighting agencies and supporting programs across the United States use this information to brace for fire seasons and react to active wildfires.

“Landsat data is critical to LANDFIRE’s mission so we, too, are celebrating this important 50th year anniversary of Landsat. LANDFIRE could not have become the gold standard of national-scale vegetation, fuels, and fire regime products without the amazing imagery provided by this satellite,” said LANDFIRE Project Manager Tim Hatten with the USGS.

Legacy of Landsat

Black and white photo of rocket on launch pad
A Delta rocket containing Landsat 1, then called Earth Resources Technology Satellite, or ERTS, sits on the launch pad at Vandenberg Air Force Base in California in July 1972. NASA photo

When the first Landsat launched in 1972, with the original name of Earth Resources Technology Satellite (ERTS), it carried more than a space experiment—it carried a dream. That dream has been realized in the 50 years since, as seven more Landsat satellites launched successfully, with increasingly improved capabilities. That dream also led to a global science and technology revolution in remote sensing Earth observation.

Landsat’s optical sensors have shown us more about the planet and its resources than we ever could have seen from eye level. Imagery from the present and past reveals the effects humanity has on nature, and nature on humanity. Understanding ecosystem composition, reactions, and patterns is key to our future.

Landsat has helped us discover unknown mineral deposits, islands, Arctic and Antarctic features, remote fires, and even rivers and forests. It has helped us understand and manage the threats against us and the beauty before us. It has shown us where we’re doing something right and where we could do better. Researchers at EROS have played a significant role in all of this, and others at EROS hold the responsibility of managing and distributing the data, preserving it for the benefit of mankind.

Between the launches of the first two Landsats, in 1972 and 1975, then-NASA administrator James C. Fletcher foreshadowed the value of the program’s mission. “If I had to pick one spacecraft, one Space Age development, to save the world, I would pick ERTS and the satellites which I believe will be evolved from it later in this decade.” 

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