Navigation satellites help pilots and sailors find their exact positions in all kinds of weather. Navigators can use it to find their position much as they would use a star. But instead of looking at the satellite, they listen to its radio signals. Resource satellites are used to monitor Earth's natural resources. This series include such satellites as Landsat and Seasat.
Scientific satellites carry a variety of instruments around the world.
Satellites that explore the upper parts of the atmosphere by beaming radio waves down into the atmosphere and then measure the reflected signals are called topside sounders. Orbiting observatories are the largest and most complicated of the scientific satellites. The orbiting geophysical observatory explores space near Earth, and scientists use it to study how the Earth's magnetic field affects energy coming from the sun. The orbiting solar observatory studies the sun by measuring radiation that cannot get through the Earth's atmosphere. The orbiting astronomical observatory looks deep into space at stars and galaxies measuring rays that never reach Earth.