USGS - U.S. Geological Survey
09/19/2024 | Press release | Distributed by Public on 09/19/2024 12:15
End of an era: Historic Landsat 7 mission takes final images
A joint mission between the U.S. Geological Survey (USGS) and NASA, Landsat 7 was initially designed for a five-year mission. Beating the odds, the satellite observed the Earth for a quarter-century, delivering invaluable scientific data for the benefit of all humanity.
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Illustration of Landsat 7 in orbit
Landsat 7 captured one of its final images on May 28 over Las Vegas, Nevada.
These Landsat 7 images showcase the first and last captures of the Las Vegas area, taken on July 4, 1999, and May 28, 2024, respectively. The images highlight the city, the surrounding desert landscape, and Lake Mead, using shortwave infrared (SWIR), near-infrared (NIR), and red bands to emphasize differences in vegetation, water, and urban growth. The final image, marking the satellite's 25th anniversary, stands as a tribute to Landsat 7's quarter-century legacy of Earth observation.
Since its launch on April 15, 1999, Landsat 7 provided a wealth of imagery, enabling scientists, policymakers, and conservationists to track changes in land use, natural disasters, and environmental degradation with unprecedented accuracy.
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Landsat 7 was successfully launched on April 15, 1999, from the Western Test Range of Vandenberg Air Force Base, California, on a Delta II expendable launch vehicle.
"Landsat 7 data have been pivotal in documenting environmental changes such as natural disasters, deforestation, and urban growth over its 25 years," said David Applegate, USGS Director. "Notably capturing significant events like Hurricane Katrina in 2005, the Haiti earthquake in 2010, the Australian bushfires in 2019 - 2020, the dramatic growth of cities worldwide and more through its long-standing mission."
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This true-color image was taken by the Enhanced Thematic Mapper Plus (ETM+) sensor aboard the Landsat 7 satellite on September 12, 2001, at roughly 11:30 a.m. Eastern Daylight Savings Time. A day after the attack, smoke continues to billow out of the collapsed Twin Towers.
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These Landsat 7 images show the damage that New Orleans, Louisiana, received as a result of Hurricane Katrina.
The data have proven to be a useful asset as the foundation for countless studies, enhancing our understanding of agriculture, water resources, and wildland fires. By providing consistent data every eight days in conjunction with Landsat 5 until 2012, Landsat 7 improved our ability to monitor seasonal changes. Thanks to operational enhancements, Landsat 7 nearly doubled the daily data collected, from 250 to 450 scenes.
The Land Imaging Satellite that Could
When it was launched, Landsat 7 featured the Enhanced Thematic Mapper Plus (ETM+) sensor, which built upon and improved the capabilities of its predecessors, the Thematic Mapper (TM) sensor used on Landsat 4 and Landsat 5. As an eight-band, multispectral scanning radiometer, the ETM+ offered improvements over previous sensor technology including a 15-meter spatial resolution panchromatic band and 60-meter resolution thermal band.
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This color infrared image of Southeast South Dakota was advertised as the first image acquired by Landsat 7's Enhanced Thematic Mapper Plus (ETM+) sensor on April 18, 1999. The Missouri River flows from the middle left of the image, to the lower right, where the Fort Randall Dam creates Lake Francis Case.
However, four years after Landsat 7's launch, a piece of equipment known as the Scan Line Corrector failed on the ETM+, impacting the satellite's ability to capture complete images of the Earth's surface. This led to "striping," or gaps in its data. Despite the setback, 78 percent of a scene's pixels are still usable and are considered some of the world's most geometrically and radiometrically accurate civilian satellite data.
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A Landsat 7 SLC-off Scene Example
Landsat 7 went on to produce images for five times its expected operational lifespan.
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For 25 years, the Landsat 7 satellite acquired millions of images of Earth that supported studies of how land is used and how it has changed across urban, agriculture, forest, snow and ice-covered areas around the globe, as well as natural and manmade disasters. As the mission comes to a close, we look back at the magnitude and impact that Landsat 7 imagery brought to scientists and those interested in studying the Earth's landmasses: Over 5,000 scientific publications in 21 languages across 143 different countries152 of the articles have received a news, blog, and/or patent mention1,414 policy documents across 54 countries that cite 749 journal articles
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This image captured by Landsat 7 shows a spinning formation of ice, clouds, and low-lying fog off the eastern coast of Greenland.
To allow Landsat 9, launched in September 2021, to share the same orbital position as Landsat 8, the USGS lowered Landsat 7's orbit. Even at its lower altitude, Landsat 7 continued to collect valuable data. However, being lowered caused Landsat 7 to increasingly drift within its orbit. The drift exposed it to periods of full sunlight and earlier imaging times, impacting battery maintenance, imaging opportunities, and processing of reliable science data. As a result, the USGS decided to end imaging from the aging satellite.
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A series of rocky outcroppings are a prominent feature of this Sahara Desert landscape near the Terkezi Oasis in the country of Chad captured by Landsat 7.
Today, Landsat operates with two satellites, Landsats 8 and 9, that work together to compile a complete set of Earth land images every 8 days.
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Landsat 7 captured Guinea-Bissau is a small country in West Africa. Complex patterns can be seen in the shallow waters along its coastline, where silt carried by the Geba and other rivers washes out into the Atlantic Ocean.
The Landsat Mission Continues
With the end of Landsat 7's role in the Landsat science mission and the advancing age of Landsat 8, launched in 2013, attention is now directed toward the Landsat Next mission as a critical next step to ensure continuity of Landsat's unique global Earth science mission. The USGS is currently focused on ensuring the flow of data remains uninterrupted and that the quality of information keeps pace with evolving technological and environmental demands.
The newest mission, known as Landsat Next, promises enhanced capabilities over its predecessors, including improved spatial resolution, increased spectral bands, and faster revisit times. These advancements are essential for more detailed and frequent monitoring of Earth's changing landscapes and for supporting critical decisions in climate resiliency, disaster response, agriculture and water management.
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Landsat Next satellites circling the Earth. The mission is planned for late 2030/early 2031.
Landsat Next is designed not only to continue the legacy of Landsat, but also to innovate and adapt to the pressing challenges of the 21st century, ensuring that scientists, policymakers, industry, and the public have access to the information needed to better monitor and sustainably manage our ever-changing planet.