text: Unless corrections are made, orbits are usually elliptical; perigee is the point on the orbit closest to the earth, and apogee is the point farthest from the earth. Besides this eccentricity an orbit of a satellite about the earth is characterized by its plane with respect to the earth. \n\nAn equitorial orbit lies in the plane of the earth's orbit. A polar orbit lies in the plane passing through both the north and south poles. A satellite's period (the time to complete one revolution around the earth) is determined by its height above the earth; the higher the satellite, the longer the period. At a height of 200 mi (320 km), the period of a circular orbit is 90 min; at 500 mi (800 km), it increases to 100 min. At a height of 22,300 mi (36,000 km), a satellite has a period of exactly 24 hr, the time it takes the earth to rotate once on its axis; such an orbit is called geosynchronous. If the orbit is also equatorial, the satellite will remain stationary over one point on the earth's surface.