One of NASA’s latest missions involves the Landsat 8, an orbiting satellite whose purpose it is to map the Earth and track changes as seen from space as it collects remote sensing data.
The National Aeronautics and Space Administration has been launching Landsat satellites into space since the early 1970s. The first Landsat satellite was launched in 1972.
The Landsat archive, managed by the USGS Earth Resources Observation and Science (EROS) center, represents the world’s longest and continuous space-based imaging of changes on the Earth’s surface. All archived Landsata data from 1972 to the present is available for free from the USGS’s EarthExplorer mapping interface.
More than four decades later, NASA, in partnership with the U.S. Geological Survey, developed the Landsat Data Continuity Mission (LDCM) also known as the Landsat 8. This satellite has the potential to play a large role in collected data related to changes in the Earth’s geographical structure.
Launch of Landsat 8
The Landsat 8 was launched on February 11, 2013 from Vandenberg Air Force Base in California. The project is the result of collaboration between NASA and the U.S. Geological Survey (USGS) within the Department of the Interior.
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The purpose of the satellite is to monitor the Earth and to keep track of changes on the planet’s surface from the impact of both nature and humans. Geographic changes are happening at a rapid place, and scientists hope to keep an eye on how the Earth is being influenced.
Throughout its five-year mission, the satellite will be under control of the USGS, and there are plans to process the data from the Landsat and distribute it over the Internet.
Replacing Landsat 5 and Landsat 7
The hope is that the satellite will fill in the missing gaps caused by malfunctions with earlier Landsat satellites.
In 2003, the Landsat 7 suffered a horrible malfunction that left two thirds of each of its images usable. Scientists had to instead rely on the Landsat 5 with its the Thematic Mapper (™) sensor, but that satellite was decommissioned earlier this year.
The time was ripe for the launch of the Landsat 8. To accomplish its mission, the Landsat 8 is equipped with state-of-the-art imaging technology and other advancements to better collect data. The satellite has sensors that allow it to pick up wavelengths of light invisible to the human eye.
The imagery collected by Landsat 8 will have a higher resolution than Landsat 1-5 which collected imagery at 60 meter spatial resolution.
Data Collection from Landsat 8
One of the instruments that the Landsat 8 will use in its data collection is the Operational Land Imager, or OLI sensor which will collect imagery at a spatial resolution of 30m.
Landsat 8 acquires data in 11 bands from two separate sensors
The LDCM picks up eleven bands of wavelengths on the electromagnetic spectrum, and the OLI collects the light reflected from the Earth’s surface from nine of these bands.
These bands on the shorter side of the wavelengths include the red bands, green bands, and visible blue. Those wavelengths on the longer side that are picked up by the OLI include the near infrared and the shortwave infrared.
The other instrument the Landsat 8 uses is called the Thermal Infrared Sensor (TIRS). This device picks up light coming from the surface on the earth in the two wavelengths called the thermal infrared. The TIRS measures different intensities of the light as different surface temperatures. This is why cooler areas on the surface are dark while warmer areas are bright.
Getting the First Images from Landsat 8
Some of the first images from the Landsat 8 came in on March 21, 2013 and can be accessed from the Landsat 8 Data Product page.
The first image was taken of the United States, where the plains of the Midwest come in contact with the Rocky Mountains of Wyoming and Colorado.
Higher resolution imagery from Landsat 8
Scientists were stunned by the quality of images the satellite produced and have high hopes for its future. The satellite took data collected from the OLI spectral bands of blue, green, and red and created a natural color image of the area that included the urban areas of Fort Collins, Denver, Cheyenne, Boulder, Longmont, and Loveland. The resulting images have 30-meter pixels of resolution.
The satellite also took another image using the OLI spectral bands of green, near infrared, and shortwave infrared. The result was an incredibly distinctive image of the Earth’s surface and scientists at the Goddard Space Flight Center were able to make different features.
For example, scientists noticed a dark strip to the left of Horsetooth Reservoir, the aftermath of the Galena wildfire. They were also able to notice clouds in the upper atmosphere.
One of the reasons that the Landsat 8 is able to take such unique images is that it takes images differently from previous Landsat satellites.
Whisk-broom sensing
In the past, these satellites used a process that LDCM scientists called whisk-broom sensing. The satellites had detectors with mirrors that moved across the field of view, and the mirrors themselves alternated back and forth several times a second. This means that the detectors could only view a plot of land for a few microseconds.
Landsat 8 has more accurate sensors than previous Landsat missions
Landsat 8, however, uses a different technique by pushing the field of view along its flight path, known as a push broom motion. This means that the detectors have a longer amount of time to pick up data for a certain piece of land. The sensors are allowed to be much more accurate.
Benefits of Landsat 8
Scientists from NASA and the USGS hope that the images from the Landsat 8 will have several benefits. The picture of the Fort Collins area showing the burned area from the Galena wildfire could help Burned Area Response teams manage wildfire recovery efforts while the ability to measure different surface temperatures could be beneficial for water management, especially in the western U.S. where irrigation is critical.
The images from the Landsat 8 could also be used to monitor agricultural practices, road and city construction, deforestation, and changes in sea ice among others.
In order to carry out its mission, the next step for the Landsat 8 is the calibration of its instruments. Settings on the spacecraft have to be adjusted so that it can accurately measure the light that its sensors pick up. One of the ways that scientists will perform reference checks on the instruments is by having the instrument view landscapes with relatively stable light properties.
Scientists are hopeful that once the satellite begins routine operations, it will help humans make more sense of the rapid changes taking place on the surface of the Earth.
This article was originally published on April 17, 2013 and has since been updated.
References for Landsat 8
“Landsat 8 Pushes the Earth-Monitoring Envelope” http://www.technewsworld.com/story/77283.html
“A Closer Look at LDCM’s First Scene” http://www.technewsworld.com/story/77283.html
“First Images from Landsat 8 Begin to Roll In.” http://www.gearthblog.com/blog/archives/2013/03/first_images_from_landsat_8_begin_t.html
“Landsat Data Continuity Mission (LDCM) – Landsat 8.” http://landsat.usgs.gov/LDCM_Landsat8.php
“Landsat 8 (LDCM) History.” http://landsat.usgs.gov/about_ldcm.php
“NASA Landsat Program on Twitter.” https://twitter.com/NASA_Landsat
