Most environmental satellites are in one of two orbits: geostationary or polar. This diagram depicts NOAA's satellite constellation as well as satellites operated by other organizations across the world. NOAA provided the image.
Geostationary satellites orbit the Earth at about 36,000 miles (58,000 km) above the surface. These satellites stay over a single spot on the ground as they circle the planet once every 24 hours. As long as there is energy stored in a battery or solar panels, the satellite will continue to send back images. Since geostationary satellites don't move, people can build large telescopes that are constantly pointed at them; these telescopes are called "geostationary observatories."
Polar-orbiting satellites fly over each continent twice daily, from both the north and south poles. Because they make two passes over each region, scientists can study changes that occur during the course of one day or over several months. For example, scientists can monitor deforestation by Earth Observatory U.S.A.
These are only some examples of how environmental agencies use satellites to learn more about our home. There are many others!
As we create more and more technology for use in space, new ways will be found to use these tools for good on Earth.
Geostationary ("geo" for short) and polar-orbiting satellite orbits are the two most common kinds. Until 1975, all satellites orbited the earth's equator. Polar-orbiting satellites travel at low altitudes, circumnavigating the Earth once every 100 minutes and covering the whole globe. Geostationary satellites remain in a fixed position above any particular spot on Earth, allowing them to observe that area continuously.
Satellites can also be classified by their purpose. Environmental satellites monitor the state of the environment on land and in the ocean. They provide data on climate change, pollution, tectonics, and other topics related to geography and earth science. Security satellites help ensure peace through surveillance of military activities and developments. Communication satellites allow for voice and data communication across large distances on land, underwater, and in space. Science satellites carry out research programs for universities and government agencies. Examples include NASA missions and probes sent to other planets.
This list is not exclusive or complete; many other types of satellites have been built for various purposes. For example, meteorological satellites collect data on weather conditions on Earth. They help scientists better understand how our planet works as a system. Satellites also play an important role in global communications. Satellites serve as relays for phone calls and data transmissions between regions of the world where there is no direct line of sight between stations on Earth.
Satellites are classified into nine types: communications satellites, remote sensing satellites, navigation satellites, LEO, MEO, HEO, GPS, GEOs, Drone Satellites, Ground Satellites, and Polar Satellites. Communications satellites transmit radio signals to terminals on the ground or between different locations. Remote sensing satellites collect information about Earth's surface using various instruments such as cameras and radar. Navigation satellites contain equipment for providing accurate time at many points across the globe. LEO (Low Earth Orbit) satellites orbit around Earth at a lower altitude than GEO (Geostationary Earth Orbit) satellites. These include most commercial communication satellites. MEO (Medium Earth Orbit) satellites travel in orbits between those of LEO and GEO. HEO (High Earth Orbit) satellites orbit around Earth at a higher altitude than GEO. These include some government-owned communication satellites. GPS (Global Positioning System) satellites enable users with GPS receivers to know their current location anywhere on Earth down to within a few hundred meters. The U.S. military developed this system and licenses it out to companies like Google for use on their smartphones.
Drone satellites carry out tasks assigned by operators on the ground. They may be used for surveillance, monitoring, or performing tasks such as spraying crops with water or delivering goods. Ground stations control drone satellites' movements and operations from onboard computers.
A weather satellite is a type of satellite that is used to monitor the Earth's weather and climate. Satellites can be in polar orbit (covering the whole Earth asynchronously) or geostationary orbit (covering the entire Earth synchronously). The World Meteorological Organization (WMO) maintains an official list of meteorological satellites, which includes both polar-orbiting and geostationary spacecraft.
Satellites provide information about clouds, rain, snow, ice, volcanoes, earthquakes, tides, floods, wild fires, and other elements related to weather and climate. This information allows scientists to understand how these processes affect life on Earth.
In addition to being useful for monitoring local weather events, satellites also help scientists understand long-term changes in the Earth's environment by observing how landmasses are affected by erosion, glaciers grow and shrink, and sea levels rise and fall.
Many types of scientific data are collected by meteorologists using different instruments aboard weather satellites. These include cameras that capture images of earth at regular intervals; radiation detectors that measure levels of ultraviolet light, X-rays, and gamma rays from solar flares and other sources; magnetometers that measure magnetic fields around the planet; and others.
Weather satellites play an important role in ensuring our safety by helping officials predict storms that could lead to accidents such as air crashes or water disasters.