Landsat program

The Landsat program is the longest-running project that has taken pictures of Earth from space. It is a joint effort by NASA and the USGS. It began on 23 July 1972, when the Earth Resources Technology Satellite was launched. This satellite was later renamed Landsat 1. The most recent satellite, Landsat 9, was launched on 27 September 2021.

The instruments on Landsat satellites have captured millions of images. These images are stored in the United States and at Landsat stations around the world. They are very useful for studying changes on Earth and for many applications, such as agriculture, cartography, geology, forestry, regional planning, surveillance, and education. People can view these images on the U.S. Geological Survey's "EarthExplorer" website.

Landsat 7, for example, can capture data in eight different colors of light, with details as small as 15 to 60 meters across. It takes pictures of the same area every 16 days. Landsat images are usually split into sections called scenes, each covering an area about 115 miles long and wide.

History

In 1965, William T. Pecora, the director of the United States Geological Survey, suggested using satellites to study Earth's natural resources. At that time, weather satellites had been watching the atmosphere since 1960, but no one had thought much about watching land from space.

Landsat began in 1966 when the Department of the Interior (DOI) decided to create an Earth-observing satellite. NASA started building the first satellite, and by 1972, Landsat 1 was launched, starting a new way to watch Earth from space. The program helped scientists study crops, forests, and many other parts of our planet.

Satellite chronology

Timeline

Spatial and spectral resolution

Landsat satellites have different tools to capture images of Earth. Landsat 1 through 5 used a tool called the Multispectral Scanner. Landsat 4 and 5 used both that scanner and another tool called the Thematic Mapper. Landsat 7 used an improved version called the Enhanced Thematic Mapper Plus. Landsat 8 uses two tools: the Operational Land Imager for normal light and the Thermal Infrared Sensor for heat images.

The size of each picture piece, or pixel, changes between the different tools. Original pictures from the Multispectral Scanner were a bit blurry, but systems now make them clearer. Other tools also adjust their pictures to make them easier to use.

One good thing about Landsat images is that they can show the whole Earth in a way that ground measurements cannot. However, there are some limits. Landsat images are not as detailed as pictures taken from airplanes, and they do not visit the same spot as often as some other satellites.

MultiSpectral Scanner (MSS)

The Landsat program used the Multispectral Scanner (MSS) from its first mission up to its fifth. The MSS helped the United States stay ahead in satellite imaging, allowing Landsat to launch before the French SPOT satellite.

The MSS was special because it used a moving mirror instead of a regular camera. This mirror captured images of Earth in four different colors of light, showing how much sunlight reflected from the Earth there was. Landsat 3's MSS could even detect heat radiation, making it even better.

The MSS was known for taking clear and consistent pictures. Each picture showed an area about 83 meters long and 68 meters wide. The system was set up to keep moving smoothly, covering a path 185 km wide on Earth's surface. It was very careful about how it moved the mirror, so the pictures would line up just right.

Later, in the 1980s, it became more expensive to get pictures from Landsat. Because of this, many people started using the French SPOT satellite instead, as its pictures were cheaper. This change happened because of decisions made by leaders in the United States.

Uses of Landsat imagery

Landsat data helps scientists understand how animals live and how places change over time, both naturally and because of humans. The satellites used in the Landsat program can see Earth in different colors, which helps with many jobs, like studying plants and animals or looking at how countries are used.

Landsat imagery has been taken since 1972, giving us a long and unbroken record of how Earth looks from space. In 2021, Landsat 9 was launched, so we can keep learning about our planet for many years to come.

Landsat imagery helps save money. In 2015, it was found that the top 16 ways people use Landsat data save governments, groups, and businesses between about 350 million and over 436 million dollars each year. These uses include helping farms, mapping for the government, watching over forests, and planning for fires. Other uses include studying fish, watching glaciers, and even finding new animals.

Landsat imagery has helped us learn about big changes on Earth, like how some lakes are getting smaller or how forests are changing. It has also helped us understand big fires, like the ones in Yellowstone National Park in 1988. By looking at pictures from space, scientists can see how different places react to fires and why some fires spread faster than others.

Landsat imagery also helps us see how cities grow and change over time. For example, in Beijing, we can watch how new roads and buildings appear after important changes in how the city is managed. In 2005, Landsat pictures helped a scientist find a new area in Mozambique that turned out to be home to many new kinds of animals, including butterflies and a snake.

Recent and future Landsat satellites

Landsat 8 launched on February 11, 2013. It was sent into space on an Atlas V rocket from Vandenberg Air Force Base. This satellite helps us learn about farming, teaching, business, science, and more. It was built in Arizona.

Landsat 9 launched on September 27, 2021. Plans for this satellite started a few years earlier. In the future, Landsat may work together with other satellites like the ESA's Sentinel-2.

Landsat Next is expected to launch around late 2030 or early 2031. It will collect information in 26 different ways, more than the 11 ways used by Landsat 8 and 9 today.