A new satellite will build on five decades of Earth observations
Landsat 9 is a partnership between NASA and USGS. The satellite will continue the Landsat program’s mission to capture repeat snapshots of Earth to monitor, understand and manage natural resources.
RESTON, Va. (U.S. Geological Survey PR) — It’s 7 o’clock on a Tuesday morning. As you decide what kind of cereal to have, you accidentally splash a bit of almond milk onto your cotton pajama top. The last thing on your mind is a pair of satellites orbiting Earth over 400 miles away.
And yet, those satellites are a part of your morning routine. They tell farmers how much water their almond trees need to thrive and reveal how soil once used for cotton is now used for fruit.
The Landsat series of satellites has been watching our planet for nearly 50 years, capturing changes on land and making that information freely available to users around the world. Currently, Landsat 7 and 8 are in orbit and collectively sending back 30-meter resolution images on an 8-day cycle.
In a week, a new era will begin. Landsat 9 is slated to launch on September 27, 2021 from Vandenberg Space Force Base in Lompoc, California. It will enter Landsat 7’s current orbit and largely replicate Landsat 8’s capabilities to provide a seamless continuation of data. Landsat 7 will lower its orbit, ending its 22-year sojourn of capturing images around Earth.
The Landsat mission is a partnership between NASA and the USGS. The former is in charge of building and launching Landsat 9 and the latter operates the satellite and distributes data for its estimated 7-year service life.
The Landsat mission is especially useful for teasing out land changes that could contribute to climate change, like deforestation, and that are caused by climate change, like intense wildfire burn scars. Landsat also sees drought conditions, tracks retreating icesheets, monitors vegetation, observes permafrost and pinpoints viable habitats. Landsat 9 will continue to provide information about natural and economic resources for scientists to study and land managers to act.
“As the global population surpasses eight billion people, it will be important to effectively manage land to sustain life on Earth,” David Applegate, the acting director of USGS, said. “Landsat 9 will pair with Landsat 8 to greatly improve our understanding of what is driving changes to our lands, surface waters, and coasts, and how we can sustainably manage it,” Applegate said.
Launching a legacy
Almost exactly 55 years ago on Sept 21, 1966, William Pecora, the 8th director of the USGS, and Stewart Udall, a former Secretary of the Interior, announced Project EROS: An Earth Resources Observation Satellite Program.
“EROS is a program aimed at gathering facts about the natural resources of Earth from Earth-orbiting satellites carrying sophisticated remote sensing observation instruments,” Udall said in a press release.
Once the program received funding, it charged NASA to build the first satellite. NASA worked with contractors to build the satellite’s sensors and systems, including Virginia Norwood, an engineer at Hughes Aircraft Company in El Segundo, CA. Many in the industry call Norwood the “Mother of Landsat” because of her pivotal work in developing a sensor able to scan the landscape, line by line, in rapid succession, as the satellite orbited Earth. The first Landsat launched from Vandenberg on July 23, 1972 and sent back an image within a few days.
Landsat 9 continues the mission’s endeavor to scan the landscape, albeit with more advanced sensors. It will carry the Operational Land Imager 2, which will capture images of Earth in visible, near infrared and shortwave-infrared light, and the Thermal Infrared Sensor 2, which will measure the heat (or brightness) of Earth’s surfaces. Both instruments’ predecessors are aboard Landsat-8.
“Exciting as it is, Landsat 9’s launch is not an end, but a beginning,” Kevin Gallagher, the associate director for Core Science Systems at USGS, said. For even before Landsat 9 was fully built, NASA and USGS started considering possibilities for the next generation of satellite, called Landsat Next. Landsat Next’s design will be driven by a thorough and peer-reviewed user requirements process managed by USGS.
Scanning for Science
Landsat’s nearly 50-year record has transformed our understanding of regional, national and global-scale agriculture, forestry, urbanization, hydrology, disaster mitigation and other changes in land use.
For example, Landsat reveals connections between farmers’ decisions and climate. “Their decision on what, when and how to irrigate crops can impact climate,” Matt Schauer, a scientist contractor to the USGS, said. He used Landsat data to measure evapotranspiration, a measure of evaporation and transpiration that includes plants’ breathing, as a proxy for water use.
Landsat 8 and 9 will capture nearly 1,500 new scenes a day to support the USGS Landsat archive. Landsat 9, like its predecessor, will also image all global landmasses and nearshore coastal regions, which were not routinely collected prior to Landsat 8.
“The more Landsat the better,” Schauer said. Landsat 9 data will be freely available for download through the USGS Earth Resources Observation and Science Center.
Landsat has a long history of mapping Antarctica and Greenland’s ice sheets. The multispectral scanner sensors on Landsats 1, 2 and 3 collected some of the earliest satellite images of coastal and interior Antarctica in the 1970s. By comparing nearly 50-year-old Landsat images to those collected more recently, scientists can pinpoint differences. “A growing archive of Landsat images allow us to see how quickly icesheets are changing,” Theodore Scambos, Senior Research Scientist at the Earth Science Observation Center at University of Colorado, said.
Landsat 9 offers an advanced capability to measure the amount of light reflected off the landscape, which will allow scientists to further characterize the exact brightness of snow and track ice motion and temperature, Scambos said. “Looking at a pair of Landsat images we can see the surface of a glacier and note how it’s changed in 2 to 3 years,” Scambos said. Melting of glaciers and ice sheets will be the biggest contributors to sea level rise this century.
Using Landsat 8 and 9, researchers can also map where the ice is melting and track the formation of meltwater ponds on the surface – both phenomena indicate how glaciers have retreated.
Tracking permafrost changes
Erin Trochim, a professor at the University of Alaska, Fairbanks, is aggregating datasets from the Landsat archive to track global surface water. In particular, she’s interested in seeing how surface water in the northern hemisphere compares to permafrost, which is permanently frozen ground and critical to the Arctic.
Trochim used Google Earth Engine to process 30 years’ worth of Landsat data. This cloud-based tool connected her to a supercomputer, which meant she could do simple processing of the entire Landsat archive in minutes.
“We identified water and found areas that have changed from water to land between 1984 and 2018,” Trochim said. She also created an app to better visualize those changes and found that more water is taking over land than vice versa.
Even though Trochim examines water from a 400-mile perspective, she likes to bring it back to the landscape by visualizing a boat filled with fish on the Yukon River. “In these huge studies, it’s easy to forget what it’s like to actually live on the river,” she said. “We want to be able to give people on the ground answers to their questions about changes they’re seeing.”
Kevin Buffington, an ecologist at USGS, examined Landsat’s long record and learned how climate variability affects the the growing season for tidal marsh plants in the Pacific Northwest. “The changes are subtle and only reveal themselves with a long-term dataset, like Landsat’s,” Buffington said.
Tidal marshes sit at the interface between ocean and freshwater. As climate change brings warmer temperatures, tidal plants are likely to bloom earlier than they have historically during their growing season. Furthermore, the plants depend on plenty of rainfall to limit salt buildup in the soil. Landsat images through time revealed that with more rain, the plants became greener.
“Tidal marshes exist in a unique environment with a small margin for survival,” Buffington said. As climate change brings sea level rise and more frequent and intense drought conditions, these ecosystems could be compromised.
Finding climate refugia
Similar to tidal marshes, playa wetlands are also at risk from drought brought on by climate change. Playa wetlands are seasonal, or ephemeral, wetlands that form in closed basins and stay dry most of the year. Jennifer Cartwright, an ecologist at USGS, and colleagues used Landsat data to track when playa wetlands were inundated even during intense droughts. Land managers can use that information to more effectively conserve and restore playas as the climate changes.
Cartwright studied Landsat images of playas in the Sheldon-Hart Mountain National Wildlife Refuge Complex in southern Oregon and northern Nevada from 1985 to 2015. “Each playa pixel in the satellite images was coded as inundated or not,” Cartwright said. “That information allowed us to track how playa inundation responded to climate variability including droughts.”
Of the 153 playas she examined, only 4% were inundated for at least two months in each of the 5 driest years. “Under extreme droughts, a few playas could still hold water, making them potentially important habitat for local and migratory species,” Cartwright said.
Tracking a vole
The Amargosa vole has a very limited distribution. In fact, it’s so limited its global range is a remnant wetland in the Mojave Desert that’s only about a mile and a half long. Moreover, its bulrush habitat is highly fragmented and occurs in patches that in total make up less than 25 hectares (about 60 acres or 45 football fields).
“By all traditional measurements, the vole should have gone extinct,” Robert Klinger, an ecologist at the USGS, said. “But it’s been with us for tens of thousands of years.”
Klinger studies and tracks the vole using Landsat’s vegetation moisture data that show how the vole’s habitat of bulrush has been getting drier. Furthermore, the plant’s moisture level has gotten more variable, making it less reliable as a viable habitat.
Without Landsat, Klinger wouldn’t have been able to track how bulrush has changed over the past 30 years, he said. “Landsat data has helped us brainstorm ideas for water management agencies to consider to ensure water continues to flow into the vole’s habitat,” Klinger said.
The vole, which fits in a human hand, is not only a cute critter. It’s also an example of an animal that has managed to exist despite many big fluctuations in climate. “It’s a great case study on how species that appear to be most prone to extinction are able to survive,” Klinger said. However, even the vole may not be able to withstand droughts if they become more extensive and severe.
“We use Landsat derived products every week to help us analyze everything from changes in vegetation cover to species distributions to the size and severity of wildfires in the west,” Justin Welty, a biologist at USGS, said.
He’s using multiple Landsat derived products including LANDFIRE, short for Landscape Fire and Resource Management Planning Tools, is a shared program between the wildland fire management programs of the U.S. Department of Agriculture Forest Service and U.S. Department of the Interior that provides remote sensing products to support researchers and land managers. The Landsat program produces imagery that is the foundation for LANDFIRE’s vegetation and disturbance data layers.
Welty also relied on the Monitoring Trends in Burn Severity (MTBS) tool, which is an interagency program whose goal is to consistently map the burn severity and extent of large fires across all lands of the United States from 1984 to present. MTBS data are generated by leveraging other national programs including the Landsat satellite program, jointly developed and managed by the USGS and NASA.
Lastly, he uses the Rangeland Condition, Monitoring, Assessment, and Projection (RCMAP) tool, which uses Landsat data to model percent vegetation cover of eight fractional vegetation components in the western U.S. for every year from 1985 to 2020.
“The impacts of climate change will continue to cause changes in vegetation, wildfires, and species distributions. To mitigate the impacts of climate change, we need products that track and analyze those changes in near real time over massive landscapes. The Landsat satellites provide us access to a suite of products at this landscape level that help us look at the past, present, and future,” Welty said.