Landsat 4
A New Age of Earth Observing Satellites
Landsat 4 was launched on July 16, 1982, with joint control of the program by NOAA, NASA, and the U.S. Geological Survey. Each federal agency took on a different role.
NASA provided launch services; NOAA initially oversaw satellite operations. Landsat 4 operations were contracted out to the Earth Observation Satellite Company (EOSAT) corporation in 1984, and the USGS archived records and distributed data. The mission was unique in that it was the first observatory to use the Thematic Mapper (TM). The sensor had seven spectral bands, three in visible part of the spectrum and four in the infrared.
Glaciers
Water, water everywhere. Our planet has more surface covered with water than land, and much of that water is held in cold storage. Glaciers, like the Columbia Glacier in Alaska, both record Earth's climate in their dense layers of ice and affect the climate when their white surfaces reflect solar radiation back into space.
The series of images in this video were gathered by Landsats 4, 5, and 7 from 1986 to 2011, and show that Columbia Glacier in Alaska’s Chugach Mountains is in decisive retreat. The false color images show ice in blue and vegetation in green. The dark blue of ocean water has opened and crept 12 miles (20 kilometers) up the mountain where the glacier used to be. Columbia Glacier is a tidewater glacier meaning it enters the sea when ice melts or calves off. Such glaciers have retreated rapidly during the last century.
Columbia is one of many vanishing glaciers around the world. Glacial retreat is one of the most direct and visible effects of climate change. Alpine glacier decline contributes to global sea level rise. According to a 2009 study by the U.S. Geological Survey , 99 percent of American glaciers are shrinking
Crop Circles
Northern Saudi Arabia hosts some of the most extensive sand and gravel deserts in the world, but modern agriculture has changed the face of some of them. This photograph from astronauts on the International Space Station presents an almost surreal view of abundant green fields in the midst of a barren desert.
As recently as 1986, there was little to no agricultural activity in the Wadi As-Sirhan Basin. But over the past 26 years, agricultural fields have been steadily developed, largely as a result of the investment of oil industry revenues by the Saudi government. Crops grown in the area include fruits, vegetables, and wheat.
The fields are irrigated by water pumped from underground aquifers. That water is distributed in rotation about a center point within a circular field—a technique known as center-pivot agriculture. The approach affords certain benefits compared to traditional surface irrigation, such as better control of water and fertilizer use. This so-called “precision agriculture” is particularly important in regions subject to high water loss due to evaporation. By better controlling the amount and timing of water application, evaporative losses can be minimized.
For a sense of scale, the agricultural fields in active use (dark green) or fallow (brown to tan), are approximately one kilometer in diameter. While much of the Wadi As-Sirhan Basin shown here is sandy (light tan to brown surfaces) and relatively flat, low hills and rocky outcrops (dark gray) of underlaying sedimentary rocks are visible at image left and right.
Below are stories from Landsat 4 or that Landsat 4 contributed data. Use the map to explore locations near you!
The Dead Sea, Over Time
Mayan Archaeology
Aral Sea, Over Time
Mount St. Helens
The Dead Sea, Over Time
The Dead Sea is named for a high salinity that discourages the growth of fish, plants, and other wildlife. This salt lake resides in a depression in the Earth's crust, where the continents of Africa and Asia pull away from each other. The Dead Sea is the lowest surface feature on Earth, sitting roughly 1,300 feet (400 meters) below sea level. On a hot, dry summer day, the water level can drop as much as one inch because of evaporation. The false color images above were captured by Landsats 1, 4, and 7. The second image was acquired on August 27, 1989, by Landsat 4.
All three images combine near infrared, red, and green wavelengths. Deep waters are blue or dark blue, while brighter blues indicate shallow waters or salt ponds (in the south). The pale pink and sand-colored regions are barren desert landscapes, while green indicates sparsely vegetated lands. Denser vegetation appears bright red. Near the center is the Lisan Peninsula, which forms a land bridge through the Dead Sea.
Mayan Archaeology
In 1978, Dr. Tom Sever became the first archaeologist to join NASA and would remain the only one for a long time. He began investigating how to apply Landsat data to the fields of anthropology and archaeology.
Sever highlighted the unique Petén ecosystem, which covers 14,000 square miles of Guatemala. A wide variety of species call Petén home. Hidden amongst the jungle are some of the most important archaeological discoveries, sites of the ancient Mayans like Tikal and El Mirador. Future sites may be discovered and explored. Deforestation in the area can destroy archaeological sites—something Landsat 4 has helped record over time.
Aral Sea, Over Time
The Aral Sea was once the fourth largest lake in the world. Situated in an otherwise desert region of Kazakhstan and Uzbekistan, two rivers, the Syr Darya and the Amu Darya, carried snowmelt and rainfall from distant mountains to pool in the Aral Basin. The Aral Sea supported farming in the river deltas and a fishing industry up through the first half of the 20th century.
Then in the 1960s, the Soviet Union converted the local economies to cotton production and diverted the two rivers to irrigate the fields. With no other major source of water, the Aral Sea has evaporated and shrank ever since. Today, the lake's area is 25 percent of its original size fifty years ago and it holds just 10 percent of its original volume of water.
Mount St. Helens
The 1980 eruption of Mt. St. Helens — which began with a series of small earthquakes in mid-March and peaked with a cataclysmic flank collapse, avalanche, and explosion on May 18 — was not the largest nor longest lasting eruption in the mountain’s recent history. But as the first eruption in the continental United States during the era of modern scientific observation, it was uniquely significant.
