|Illustration of Artemis-P1 liberations orbits. Credit: NASA/Goddard|
ARTEMIS-P1 is the first spacecraft to navigate to and perform stationkeeping operations around the Earth-Moon L1 and L2 Lagrangian points. There are five Lagrangian points associated with the Earth-Moon system. The two points nearest the moon are of great interest for lunar exploration. These points are called L1 (located between the Earth and Moon) and L2 (located on the far side of the Moon from Earth), each about 61,300 km (38,100 miles) above the lunar surface. It takes about 14 to 15 days to complete one revolution about either the L1 or L2 point. These distinctive kidney-shaped orbits are dynamically unstable and require weekly monitoring from ground personnel. Orbit corrections to maintain stability are regularly performed using onboard thrusters.
Other benefits of this first ever libration orbit mission include the investigation of lunar regions to provide a staging location for both assembly of telescopes or human exploration of planets and asteroids or even to serve as a communication relay location for a future lunar outpost. The navigation and control of the spacecraft will also provide NASA engineers with important information on propellant usage, requirements on ground station resources, and the sensitivity of controlling these unique orbits.
|A contour plot of the effective potential due to gravity and the centrifugal force of a two-body system in a rotating frame of reference. The arrows indicate the gradients of the potential around the five Lagrange points — downhill toward them (red) or away from them (blue). Counterintuitively, the L4 and L5 points are the high points of the potential. At the points themselves these forces are balanced.|
Lagrangian points L2 through L5 only exist in rotating systems, such as in the monthly orbiting of the Moon about the Earth. At these points, the combined attraction from the two masses is equivalent to what would be exerted by a single mass at the barycenter of the system, sufficient to cause a small body to orbit with the same period.
Future and proposed missions
|Deep Space Climate Observatory||Sun–Earth L1||NASA||On hold|
|LISA Pathfinder (LPF)||Sun–Earth L1||ESA, NASA||Launch Date 2014 |
|Solar-C||Sun–Earth L1||Japan Aerospace Exploration Agency||Possible mission after 2010|
|Gaia||Sun–Earth L2||ESA||Planned for August 2013 |
|James Webb Space Telescope||Sun–Earth L2||NASA, ESA, Canadian Space Agency||Working on 2018 launch|
|Euclid||Sun–Earth L2||ESA||Proposed for launch in 2019|
|Wide Field Infrared Survey Telescope||Sun–Earth L2||NASA, U.S. Department of Energy||Proposed for launch in 2020|
|“Lunar Far-Side Communication Satellites”||Earth–Moon L2||NASA||Proposed in 1968|
|Exploration Gateway Platform||Earth–Moon L2||NASA||Proposed in 2011|
|Space colonization and manufacturing||Earth–Moon L4 or L5||L5 Society||Proposed in 1974|
The Exploration Gateway Platform is a design proposed by Boeing in December 2011 to drastically reduce the cost of Moon, NEA’s, or Mars missions by using components already designed to construct a refueling depot and servicing station located at one of the Earth–Moon Lagrange points, L1 or L2. The system claims its cost savings based on an ability to be reused for multiple missions such as a launch platform for deep space exploration, robotic relay station for moon rovers, telescope servicing and a deep space practice platform located outside the Earth’s protective radiation belts.
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