Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A geosynchronous transfer orbit or geostationary transfer orbit is an intermediate orbit used to reach geosynchronous or geostationary orbit. It is a highly elliptical Earth orbit with apogee at about 35,700 km, geostationary altitude, and an argument of perigee such that apogee occurs on or near the equator. Perigee can be anywhere above the atmosphere, but is usually limited to only a few hundred km to reduce launcher delta-v requirements and to limit the orbital lifetime of the spent booster. The inclination of a GTO is the angle between the orbit plane and the Earth''s equatorial plane. It is determined by the latitude of the launch site and the launch azimuth. The inclination and eccentricity must both be reduced to zero to obtain a geostationary orbit.