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http://en.wikipedia.org/wiki/List_of_objects_at_Lagrangian_points

This is a list of known objects which occupy, have occupied, or are planned to occupy any of the five Lagrangian points of two-body systems in space.

A diagram showing the five Lagrangian points in a two-body system

Sun-Earth Lagrangian points

L₁

L₁ is the Lagrangian point located approximately 1,500,000 km towards the Sun away from the Earth.

Past probes

• International Cometary Explorer, formerly the International Sun-Earth Explorer 3 (ISEE-3), diverted out of L₁ in 1983 for a comet rendezvous mission. Currently in solar orbit, it may be captured in 2014 when it next approaches Earth.
• NASA's Genesis probe collected solar wind samples at L1 from December 3, 2001 to April 1, 2004, when it returned to Earth.

Present probes

• GGS WIND
• The Solar and Heliospheric Observatory (SOHO)
• The Advanced Composition Explorer (ACE)

Planned probes

• LISA Pathfinder
• Kuafu

Cancelled probes

• The Triana satellite, designed to monitor global warming.

L₂

L₂ is the Lagrangian point located approximately 1,500,000 km away from the Earth in the direction opposite the Sun.

Past probes

• GEOTAIL

Present probes

• Wilkinson Microwave Anisotropy Probe (WMAP)

Planned probes

• The joint NASA, ESA and CSA James Webb Space Telescope (JWST), formerly known as the Next Generation Space Telescope (NGST)
• The ESA Herschel Space Observatory
• The ESA Planck Surveyor
• The ESA Gaia probe
• The NASA Terrestrial Planet Finder mission (may be placed in an Earth-trailing orbit instead)
• The ESA Darwin mission
• The NASA Advanced Technology Large-Aperture Space Telescope, that will replace both the Hubble Space Telescope and JWST.

Cancelled probes

• The ESA Eddington mission

L₃

L₃ is the Lagrangian point located on the side of the Sun opposite the Earth, slightly outside the Earth's orbit.

• There are no known objects in this orbital location.

L₄

L₄ is the Lagrangian point located close to the Earth's orbit 60° ahead of the Earth.

• STEREO A (Solar TErrestrial RElations Observatory – Ahead) The twin STEREO spacecraft passed through L4 and L5 in autumn 2009.
• Dust clouds

L₅

L₅ is the Lagrangian point located close to the Earth's orbit 60° behind the Earth.

• STEREO B (Solar TErrestrial RElations Observatory – Behind)
• Spitzer is in an earth-trailing heliocentric orbit drifting away circa 0.1 AU per year. In circa 2013-15 it will pass L₅ in its orbit.
• Dust Clouds

Earth-Moon Lagrangian points

L₂

• None

L₄ and L₅

• possible Kordylewski clouds
• STEREO A and B will search for Earth Lagrangian asteroids as they pass through the L₄ and L₅ regions, respectively, in 2010. They will have another opportunity as they loop back around through the opposite Lagrangian points several years later.
• future location of TDRS-style communication satellites to support L₂ satellite

Proposed objects

In his book "The High Frontier" Dr. Gerard O'Neill proposed the establishment of gigantic Space Islands in L₅. The inhabitants of the L5 Society should convert Lunar material to huge solar power satellites.

Sun-Mars Lagrangian points

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Published in July 2009.

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