Trans Earth Injection
From Wikipedia, the free encyclopedia
Trans Earth Injection (TEI) is a term describing the propulsion maneuver used to set a spacecraft on a trajectory which will intersect the Earth.
The spacecraft is usually in a parking orbit around moon at the time of TEI.
The maneuver is usually performed by a rather large rocket engine. On the Apollo missions it was performed by the restartable Service Propulsion System (SPS) rocket. This particular TEI burn lasted approximately 203.7 seconds, on the Lunar backside, providing a posigrade velocity increase of 3531 fps. It was first performed by the Apollo 8 mission on December 25, 1968.
The burn is timed so that the mid-point of the TEI is opposite the Earth (or more precisely, the Earth's location upon arrival).
[edit] References
- Godwin, Robert (1999). Apollo 8: The NASA Mission Reports. Burlington, Ontario, CANADA: Apogee Books, 21-23. ISBN 1896522-50-5.