In 1972, the Soviet Union experienced a major wheat crop failure. The U.S. had sold large quantities of wheat to the Soviet Union at low prices before the crop failure was announced. The failure drove up wheat prices, and the U.S. ended up buying wheat back from the Soviets at a loss. In order to add an element of stability to the world's agricultural market s, NASA and the U.S. Department of Agriculture began a program to see if Landsat data could be used to estimate global crop production. Analyzing these bands allowed the scientists to map the acreage and maturity of the wheat crop.
Vegetation reflects light differently than soil or concrete o r rooftops or trees.
Each crop has a unique pattern of reflectance, and that pattern changes as the crop develops over time. By 1976, Landsat 1 and Landsat 2 were making estimates of crop production for wheat and other grains around the globe. These estimates turned out to be accurate within 10 percent, which was the goal of the project, Hall s aid. Since the mid-1980s, scientists have increasingly used Landsat data to monitor and document global change, such as urban sprawl and deforestation. In one recent environmental application, scientists used Landsat data to document the decline of nearly 900 coral reefs around the world.