When we speak of satellites as they relate to weather, we are usually referring to man-made machines which orbit the Earth. A satellite is able to stay in orbit indefinitately because two opposing forces acting upon the satellite become equal and the satellite reaches a state of equilibrium. The force of gravity acts to try to pull the satellite toward the Earth, however, since the satellite is in a circular motion around the Earth, a centripetal force acts to push the satellite away. In a stable orbit, these two forces are equal and the satellite will travel in a circular or elliptical path around the Earth. Satellites are initially placed into orbit with rocket boosters or the Space Shuttle.
Satellites are useful for weather observation because they are at an ideal vantage point.
All weather satellites orbit high above the atmosphere well above any clouds, storms, or other weather effects. This affords a clear view of the weather patterns below. The extreme altitude also allows us to view a large area of atmosphere. Also, depending on the nature of the orbit, it is sometimes possible for a satellite to view the entire Earth in a matter of a few hours. Most weather satellites carry a wide array of instruments to allow a great number of images and measurements to be made.