This is a list of known objects which occupy, have occupied, or are planned to occupy any of the five Lagrange points of two-body systems in space.
A diagram showing the five Lagrange points in a two-body system
Sun–Earth Lagrange points
Sun–Earth L1
L1 is the Lagrange point located approximately 1.5 million kilometers from Earth towards the Sun.
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 heliocentric orbit. The Sun–Earth L1 is also the point to which the Reboot ISEE-3 mission was attempting to return the craft as the first phase of a recovery mission (as of September 25, 2014 all efforts have failed and contact was lost).[1]
NASA's Genesis probe collected solar wind samples at L1 from December 3, 2001, to April 1, 2004, when it returned the sample capsule to Earth. It returned briefly in late 2004 before being pushed into heliocentric orbit in early 2005.
LISA Pathfinder (LPF) was launched on 3 December 2015, and arrived at L1 on 22 January 2016, where, among other experiments, it tested the technology needed by (e)LISA to detect gravitational waves. LISA Pathfinder used an instrument consisting of two small gold alloy cubes.
The Chang'e 5 orbiter[2] (during extended mission. After ferrying lunar samples back to Earth in 2020, the transport module was sent to L1 where it is permanently stationed to conduct limited Earth-Sun observations.)
Mission: Investigation of the outer layer of the Sun, making observations of solar wind and associated phenomena in the vicinity of L1, probing the interior structure of the Sun.
Animation of Deep Space Climate Observatory's trajectory from 11 February 2015 to 3 January 2017 DSCOVR·Earth·Moon
The Deep Space Climate Observatory (DSCOVR), designed to image the sunlit Earth in 10 wavelengths (EPIC) and monitor total reflected radiation (NISTAR). Launched on 11 February 2015, began orbiting L1 on 8 June 2015 to study the solar wind and its effects on Earth.[3] DSCOVR is unofficially known as GORESAT, because it carries a camera always oriented to Earth and capturing full-frame photos of the planet similar to the Blue Marble. This concept was proposed by then-Vice President of the United States Al Gore in 1998[4] and was a centerpiece in his 2006 film An Inconvenient Truth.[5]
Aditya-L1 was successfully launched on 2 September 2023 and entered the halo orbit around the lagrange point on 6 January 2024.[6] It's a Solar observation mission by ISRO. It will study solar atmosphere, solar magnetic storms, and their impact on the environment around the Earth.[7]
L2 is the Lagrange point located approximately 1.5 million kilometers from Earth in the direction opposite the Sun. Spacecraft at the Sun–Earth L2 point are in a Lissajous orbit until decommissioned, when they are sent into a heliocentricgraveyard orbit.[citation needed]
Past probes
Animation of Wilkinson Microwave Anisotropy Probe's trajectory from 1 July 2001 to 7 April 2009 WMAP·Earth
2001 – 2010: NASA's Wilkinson Microwave Anisotropy Probe (WMAP)[8] observed the cosmic microwave background. It was moved to a heliocentric orbit to avoid posing a hazard to future missions.
2003 – 2004: NASA's WIND. The spacecraft then went to Earth orbit, before heading to L1.[9]
2009 – 2013:[10] The ESA Herschel Space Observatory exhausted its supply of liquid helium and was moved from the Lagrangian point in June 2013.
2009 – 2013: At the end of its mission ESA's Planck spacecraft was put into a heliocentric orbit and passivated to prevent it from endangering any future missions.
2011 – 2012: CNSA's Chang'e 2.[11][12] Chang'e 2 was then placed onto a heliocentric orbit that took it past the near-Earth asteroid 4179 Toutatis.
L3 is the Sun–Earth Lagrange point located on the side of the Sun opposite Earth, slightly outside the Earth's orbit. Direct communication with spacecraft in this position is blocked by the Sun.
There are no known objects in this orbital location. [citation needed]
Sun–Earth L4
L4 is the Sun–Earth Lagrange point located close to the Earth's orbit 60° ahead of Earth.
Asteroid (614689) 2020 XL5 is the second Earth trojan, confirmed in November 2021, oscillating around L4 in a tadpole orbit and expected to remain there for at least 4000 years, until destabilized by Venus.[13]
STEREO A (Solar TErrestrial RElations Observatory – Ahead) made its closest pass to L4 in September 2009, on its orbit around the Sun, slightly faster than Earth.[14]
OSIRIS-REx passed near the L4 point and performed a survey for asteroids between 9 and 20 February 2017.
Sun–Earth L5
L5, or Earth-trailing orbit, is the Sun–Earth Lagrange point located close to the Earth's orbit 60° behind Earth.
STEREO B (Solar TErrestrial RElations Observatory – Behind) made its closest pass to L5 in October 2009, on its orbit around the Sun, slightly slower than Earth.[14]
The Spitzer Space Telescope is in an Earth-trailing heliocentric orbit drifting away c. 0.1 AU per year. In c. 2013–15 it has passed L5 in its orbit.
Hayabusa2 passed near L5 during the spring of 2017, and imaged the surrounding area to search for Earth trojans on 18 April 2018.[15]
Future location of TDRS-style communication satellites to support L2 satellite and further regions on the Moon.[17][18]
Past probes
Hiten was the first spacecraft to demonstrate a low energy trajectory, passing by L4 and L5 to achieve lunar orbit at a very low fuel expense, compared to usual orbital techniques. Hiten did not find any conclusive increase in dust density at Lagrange points.[19]
Asteroids in the L4 and L5 Sun–Mars Lagrangian points are sometimes called Mars trojans, with a lower-case t, as "Trojan asteroid" was originally defined as a term for Lagrangian asteroids of Jupiter. They may also be called Mars Lagrangian asteroids.
Minor planets in the L4 and L5 Sun–Neptune Lagrangian points are called Neptune trojans, with a lower-case t, as "Trojan asteroid" was originally defined as a term for Lagrangian asteroids of Jupiter.
Color key: Unflown or planned mission Mission en route or in progress (including mission extensions) Mission at Lagrangian point completed successfully (or partially successfully)
Launched in 1978, it was the first spacecraft to be put into orbit around a libration point, where it operated for four years in a halo orbit about the L1 Sun–Earth point. After the original mission ended, it was commanded to leave L1 in September 1982 in order to investigate comets and the Sun.[21] Now in a heliocentric orbit, an unsuccessful attempt to return to halo orbit was made in 2014 when it made a flyby of the Earth–Moon system.[22][23]
Launched one day behind revised schedule (planned for the 100th anniversary of the publication of Einstein's General Theory of Relativity), on 3 December 2015. Arrived at L1 on 22 January 2016.[25] LISA Pathfinder was deactivated on 30 June 2017.[26]
Mission consists of two spacecraft, which were the first spacecraft to reach Earth–Moon Lagrangian points. Both moved through Earth–Moon Lagrangian points, and are now in lunar orbit.[34][35]
Proposed in 1968 for communications on the far side of the Moon during the Apollo program, mainly to enable an Apollo landing on the far side—neither the satellites nor the landing were ever realized.[45]
^"ISEE-3 is in Safe Mode". Space College. 25 September 2014. "The ground stations listening to ISEE-3 have not been able to obtain a signal since Tuesday the 16th"
