Lunar orbit

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Lunar orbit

In astronomy

Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
, lunar orbit (also known as a Selenocentric orbit) refers to the orbit

Planetary orbit

In physics, an orbit is the gravitationally curved path of one object around a point or another body, for example the gravitational orbit of a planet around a star....
of an object around the Moon

Moon

The Moon is Earth's only natural satellite and the List of natural satellites by diameter satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is km, about thirty times the diameter of the Earth....
.

As used in the space program, this refers not to the orbit of the Moon about the Earth

Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
, but to orbits by various manned or unmanned spacecraft around the Moon.

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In astronomy

Astronomy

Planetary orbit

Moon

Earth

Luna 1

Luna programme 1 , also known as Mechta was the first spacecraft to reach the vicinity of the Moon and the first of the Luna programme of Soviet automatic interplanetary stations successfully launched in the direction of the Moon....
on January 4, 1959. It passed within 5,995 km of the Moon's surface. Luna 3

Luna 3

The Soviet space probe Luna 3 was the third spacecraft sent successfully to the Moon, and it was an early feat in the human exploration of outer space....
, launched on October 4, 1959 used a figure-8 trajectory, or free return trajectory

Free return trajectory

A free return trajectory is one of a very small sub-class of trajectories in which the trajectory of a satellite traveling away from a primary body is modified by the presence of a secondary body causing the satellite to return to the primary body....
, to swing around the backside of the Moon

Far side of the Moon

The far side of the Moon is the Moon hemisphere that is permanently turned away from the Earth. The far hemisphere was first photographed by the Soviet Luna 3 probe in 1959, and was first directly observed by human eyes when the Apollo 8 mission orbited the Moon in 1968....
, and return the first pictures of the far side of the Lunar surface. The figure-8 trajectory was not a true orbit around the Moon, as the spacecraft only circled a portion of the Moon, and then went on a free return trajectory back to earth.

The Soviet Union

Soviet Union

The Union of Soviet Socialist Republics was a Constitution of the Soviet Union socialist state that existed in Eurasia from 1922 to 1991.The name is a translation of the , romanization of Russian Soyuz Sovetskikh Sotsialisticheskikh Respublik, abbreviated ????, SSSR....
's Luna 10

Luna 10

Luna 10 was an unmanned space mission of the Luna program, also called Lunik 10.The Luna 10 spacecraft was launched towards the Moon from an Earth orbiting platform on March 31, 1966....
was the first spacecraft to actually orbit the Moon

Moon

Micrometeoroid

A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeor or micrometeorite is such a particle that enters the Earth's atmosphere or falls to Earth....
flux, and lunar environment until May 30 1966.

The first United States

United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
spacecraft to enter a true lunar orbit, in the sense that it was a satellite continuously going around the Moon, was Lunar Orbiter 1

Lunar Orbiter 1

The Lunar Orbiter 1 robotic spacecraft, part of the Lunar Orbiter program, was designed primarily to photograph smooth areas of the Moon surface for selection and verification of safe landing sites for the Surveyor program and Apollo program missions....
on August 14, 1966. The first orbit was an elliptical orbit, with an apolune of 1,866.8 kilometers and a perilune of 189.1 kilometers. This was the first of five similar spacecraft launched over a period of thirteen months, all of which successfully mapped the Moon. The primary mission of the Lunar Orbiter program was to search for suitable Apollo Project landing sites.

The Apollo Project's Command and Service Module remained in lunar orbit while the Lunar Module

Apollo Lunar Module

The Apollo Lunar Module was the Lander portion of the Apollo spacecraft built for the United States Apollo program by Grumman to achieve the transit from cislunar orbit to the surface and back....
landed. Selection of an orbit was constrained on the low side by lunar mountains

List of mountains on the Moon

This is a list of mountains on the Moon:...
reaching heights of 20,000 feet (nearly seven kilometers), and on the high side by the need to obtain suitable imagery. Lunar Orbiters

Lunar Orbiter program

The Lunar Orbiter program was a series of five unmanned space mission Moon orbiter missions launched by the United States in 1966 through 1967 with the purpose of mapping the lunar surface before the Apollo program landings....
were mostly around 200 miles altitude while the Apollo Project used roughly 65 miles. Orbital periods were roughly two hours.

Gravitational anomalies slightly distorting the orbits of the Lunar Orbiters led to the discovery of Mass concentration

Mass concentration

Mass concentration can have different meaning in astronomy or chemistry.In astronomy or astrophysics mass concentration or mascon is a region of a planet or moon's crust that contains a large positive gravitational anomaly....
s ("mascons"), concentrations of mass beneath the lunar surface caused by large impacting bodies at some remote time in the past. These anomalies were too small to be of significance for the short time the Apollo Project's spacecraft were in lunar orbit.

Lunar orbit

See also