Astrogation
Encyclopedia
Astrogation is the planning of a route through space and the actual navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

 of spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

, either in interplanetary travel
Interplanetary travel
Interplanetary spaceflight or interplanetary travel is travel between planets within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the Solar System....

 or in interstellar travel
Interstellar travel
Interstellar space travel is manned or unmanned travel between stars. The concept of interstellar travel in starships is a staple of science fiction. Interstellar travel is much more difficult than interplanetary travel. Intergalactic travel, or travel between different galaxies, is even more...

. The mathematical principles governing interplanetary astrogation were derived by mathematical physicists in the 19th and 20th centuries.

Two tasks define navigation: (1) determining present location, and (2) planning a safe and reliable means of reaching a destination. An example of an interstellar approach to describing the location of Earth is the plaque
Pioneer plaque
The Pioneer plaques are a pair of gold-anodized aluminium plaques which were placed on board the 1972 Pioneer 10 and 1973 Pioneer 11 spacecraft, featuring a pictorial message, in case either Pioneer 10 or 11 are intercepted by extraterrestrial life...

 carried by the Pioneer 10
Pioneer 10
Pioneer 10 is a 258-kilogram robotic space probe that completed the first interplanetary mission to Jupiter, and became the first spacecraft to achieve escape velocity from the Solar System. The project was managed by the NASA Ames Research Center and the contract for the construction of the...

 and Pioneer 11
Pioneer 11
Pioneer 11 is a 259-kilogram robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind, cosmic rays, and eventually the far reaches of the solar system and heliosphere...

 spacecraft, where pulsar
Pulsar
A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name...

s are used as references.

Route planning is greatly affected by means of propulsion, gravitational potential, obstacles and other hazards (such as radiation), and distance or time. Since no known extrasolar star is closer than four light years away, science fiction writers commonly introduce speculative or fictional work-arounds to the awkward time problem. However, some novels such as Encounter With Tiber
Encounter With Tiber
Encounter With Tiber is a 1996 science fiction novel written by former astronaut Buzz Aldrin and science fiction writer John Barnes...

, co-authored by astronaut
Astronaut
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....

 Buzz Aldrin
Buzz Aldrin
Buzz Aldrin is an American mechanical engineer, retired United States Air Force pilot and astronaut who was the Lunar Module pilot on Apollo 11, the first manned lunar landing in history...

 (one of the few people to have set foot on the Moon), treat distance and time more realistically as part of the plot.

The term astrogation was first used by science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

writers beginning in the first half of the 20th century.
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