Satellites Studying Earth's Surface

by Jeanette Cain

Scientists are able to study the Earth's surface with the help of satellites known as Earth resources satellites. These satellites can show scientists if polar ice caps are melting, if food and resource crops are surviving, and if there are reserves of metal ores and coal resources. These satellites use instruments capable of analyzing light and other reflected materials, and any emitted radiation from Earth's surface. Scientists can study different signatures of the reflected and emitted radiation with the help of these satellites. These satellites are so well tuned that they can distinguish between a forest and a building. Scientists make maps tracing changes over a particular area of Earth's surface with the help of routine satellite schedules.

The Landsat 1 was launched by the United States in 1972, which was able to combine visible and infrared imaging of Earth's surface. The US Seasat satellite made needed measurements of Earth's ocean with the help of radar in 1978. The SPOT 1 was launched by France in 1986, which was the first Earth resources satellite using silicon chips to detect radiation. The Topex/Poseidon mission, 1992, collected ocean data in more detail than previous satellites. To date, more than 30 new satellites are planned for orbit around the Earth.

Radiation emits different wavelengths according to the different types of radiation. A thematic mapper on Landsat satellites is capable of measuring seven different wavelength bands. This includes four in the infrared area of the electromagnetic spectrum with scientists attributing a different color to each band for creating a map of a certain area. Each wavelength band of the thematic mapper can reveal different aspects of the Earth. Example: Band five can detect the range of infrared wavelengths of vegetation moisture content. It can detect changes indicating a possible failure of crops.

Landsat images have shown the forests of the Ivory Coast region in Africa with the help of identifying colors: (1) pale blue is soil; (2) red is the vegetation of forests; and, (3) brown stands for crops. The images are taken over months and years to give an idea of changes, harmful or not, within the scanned areas. Humans are unable to see infrared, so scientists give each infrared wavelength band its own identifying color, which are known as false colors. False color photography shows white as having mineral deposits, dark blue stands for water, brown stands for soil, and red stands for vegetation.

Two-thirds of Earth's surface is covered in water. Scientists need to understand Earth and its climate, so they need to know what happens in, above and around Earth's oceans. They check for levels of temperature and winds, and for ocean currents. The ERS-1 was one of the first satellites designed specifically for ocean surveillance. Satellites can keep up with happenings in these areas, whereas ships and aircraft cannot. Ocean height is the basic measurement for ocean and climate research used for information on tides and currents. The Topex/Poseidon satellite made measurements with an accuracy rating of 4.3 cm. In one month, it collected more information of the ocean than had previously been accomplished by all research ships in the last 100 years.

Sources:

1. Couper, Heather and Nigel Henbest. Space Encyclopedia DK Publishing, Inc.: NY 1999

2. Editors. Secrets of the Universe. International Master Publishing: US. 1999