An artistic interpretation of Landsat 7. Source: NASA.
Today marks the 40th anniversary of the first launch in the Landsat satellite series. Since 1972, seven Landsat satellites have been launched to gather information about Earth from space. Currently a joint venture by NASA and the U.S. Geological Survey (USGS), the Earth-observing satellite mission has helped study Earth changes made by natural processes and human practices. To date, the Landsat series is the longest continuous global record of Earth’s surface from space. Over the past 40 years, we have actively monitored our home planet close-up, thanks to the satellite program. Topics that have been studied by Landsat include: Urban growth, food production, forest and water resource use, human health, energy production, disaster relief, and climate change.
Landsat has been fundamental to our scientific understanding of the Earth. Originally, the data gathered was used to inventory Earth’s natural resources from space. Today, the Landsat program has grown to address critical issues such as water quality, glacier recessions, sea ice movement, massive species encroachment, deforestation, land use changes, coral reef health, population growth, and damages from natural disasters. These data are used for decision-making in a variety of industries, including agriculture, forestry, land use, water management, and natural resource planning. Additionally, NASA’s Land-Cover and Land-Use Change (LCLUC) Program uses Landsat data to address the physical and societal drivers of change on our planet. According to the Science Citation Index (SCI), more than 3,200 peer-reviewed articles cite Landsat data.
Wallow Fire, Arizona, Landsat 5. Image Source: NASA.
ÛÏLandsat’s greatest legacy is that it is the longest record of the Earth’s land surface as observed from space,Û says Dr. James Irons, Landsat Data Continuity Mission (LDCM) Project Scientist. ÛÏLand surface of Earth is changing at rates unprecedented in human history and therefore the result is of a profound consequence to society.Û
The satellite series, which uses 30-meter spatial resolution and 185-kilometer swath of imagery, is uniquely suited to monitor patch-scale landscape dynamics and man-made changes for the entire globe on a seasonal basis. Furthermore, rigorous instrument calibration provides a consistent time series of observations that can be used to monitor long-term changes. This provides accurate and composite data that is then used by many nations. The USGS’ National Satellite Land Remote Sensing Data Archive in Sioux Falls, South Dakota, distributes and archives all Landsat data.
Landsat has been a pioneering satellite program in providing a baseline for monitoring our changing Earth and interactions between humans and the environment. In November 2011, an Earthzine article highlighted the addition of Landsat imagery to the Memory of World International Register, to reflect the progression of mankind through time. Landsat provides maps to depict these changes and provide a fuller picture of the Earth. For example, the data has helped aid navigation in poorly chartered areas including the Arctic and Antarctic. These maps also have been able to uncover the head of the Lambert Glacier as well as an unknown mountain range in the South Victoria Land. Additionally, Landsat maps have outlined faults and fracture zones of the Earth.
(See also ÛÏLandsat: An Earth-Observing TrailblazerÛ)
ÛÏIt was the granddaddy of them all, as far as starting the trend of repetitive, calibrated observations of the Earth at a spatial resolution where one can detect man’s interaction with the environment,Û said Dr. Darrel Williams, Landsat 7 Project scientist.
Washington, D.C., in 1984, left, and 2011, right via Landsat 5. Source: NASA.
Another unique attribute of Landsat is the rapid delivery of free, unrestricted data. Developing countries use the data to monitor harmful activities to the Earth, such as deforestation or damage from natural disasters. Landsat data was used to create a baseline map of Earth’s mangrove forests, which are vulnerable to rising sea levels, through the collection of Landsat scenes from 1997-2000 (which account for 53,190 square miles of forests). Data also has been used to show forest damage as a result of Hurricane Katrina and the consequent release of a large amount of carbon into the atmosphere.
ÛÏThe records that Landsat provides exist to inform land policy, decisions, and strategies, so that we can make the best use of our resources and sustain us here on the planet. For me, that’s the core of the program,Û said Dr. Irons.
Countries, organizations, and individuals have used Landsat data for a variety of purposes. Brazil recently marked 1996-2005 Landsat data as the baseline for deforestation monitoring. By measuring the degradation of forests over time, Brazil hopes to reduce its carbon emissions and thusly be proactive in combating climate change.
Similarly, NASA has used Landsat data to understand the complex water cycle, which will be essential for future water management. Scientists agree that the strain of the growing population on water resources will only continue to worsen in rural and urban areas. Humans are dependent on water for drinking, irrigation, food production, and industrial purposes. Agricultural activity also is dependent on the fresh water cycle. Landsat’s visible and infrared image data allows land cover and open water sources to be classified, and Landsat’s thermal data allows evapotranspiration to be estimated in irrigated croplands. Landsat helps us to better understand the water problem and regulate water usage. Landsat data also is used to routinely monitor the Californian San Joaquin Valley for crop growth, irrigation demands and forecasts, and growing fields during season.
Landsat data has had other applications, including tracking glacier melt. The data has shown that the West Antarctic Ice Sheet is breaking up, accelerating the loss of ice to the sea. ÛÏAnyone can examine this region in Google Earth and see a snapshot of the same satellite data we used, but only through examination of the whole satellite record is it possible to distinguish long-term change from cyclical calving,Û said Joseph MacGregor, research science associate and lead of the glacier study.
Cyprus, Landsat 7. Source: NASA.
University of California Santa Barbara (UCSB) has used Landsat data to monitor giant kelp forest ecosystems. The information provided by Landsat 5 has shown how climate change affects the giant kelp environment. Calibrated with images taken by UCSB divers, the Landsat time series (1984-2009) documents the degradation of these ecosystems.
An Earthzine article from 2011 highlighted the use of Landsat data to monitor Mediterranean coastal wetlands. These wetlands have undergone significant changes as a result of urban growth and tourism in recent decades and may be susceptible to changes to a potential rise in sea levels. Using 35 years of Landsat data, the GlobWetland-II was able to identify the changes to the coastal wetlands and see notable decreases in natural and semi-natural areas.
An extensive list of Landsat data applications can be found here.
Landsat’s history began in 1965, when William Pecora, then director of USGS, suggested that the nation needed a civilian satellite for remote sensing of Earth’s natural resources. Additional inspiration for the project was provided by early photographs of the Earth’s surface during Project Mercury and Project Gemini missions. In 1972, the Earth Resources Technology Satellite (ERTS), later renamed to Landsat 1, was launched and became the first spacecraft to study Earth’s landmasses.
Landsat 8, known as Landsat’s Data Continuity Mission (LDCM), is set to launch in January 2013 and will continue to produce important data and imagery for Earth observation. It will use an Operational Land Imager (OLI) and a Thermal InfraRed Sensor (TIRS) to continue the Landsat legacy of providing well-calibrated, long-term, seasonal observations of the Earth’s surface at a management-scale spatial resolution.