NASA Preparing to Explore Earth-Moon Libration Point 2
February 13, 2012 12:35 PM
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The Lagrange points for the Earth-moon system
Exploration and potential use of EML-2 provide a platform for radio astronomy as well as solar and Earth observation
NASA is in the midst of developing a team that will explore an area in space called the Earth-moon libration point 2 (EML-2).
A memo released by NASA on February 3 spells out a plan for exploration beyond low-Earth orbit, where EML-2 will be one of the exploration points. The memo was written by William Gerstenmaier, NASA's associate administrator for human exploration and operations.
NASA said EML-2 could be the first step in the "capability-driven" exploration of other space sites like asteroids, the moon and Mars. U.S. President Barack Obama challenged NASA to put a man on an asteroid by 2025 and
explore Mars in 2030
There are five libration points, or Lagrangian points, which mark positions where the combined gravitational pull of two large masses provides the centripetal force needed to rotate with them. This combined gravitational pull of the two large masses balance each other out, and spacecraft is able to basically park in this stationary spot.
Exploration and potential use of EML-2, which is located
near the lunar
far side, could open up the use of telerobotic science on the far side of the moon and provide a platform for radio astronomy as well as solar and Earth observation. It could also enable assembly and servicing of satellites and telescopes. NASA sees the effort eventually creating international partnerships as well as new opportunities with commercial companies and academic institutions.
The memo plotted six strategic principles for exploration beyond low-Earth orbit, such as incorporating significant international participation that leverages current International Space Station partnerships; U.S. commercial business opportunities to further enhance the space station logistics market with a goal of reducing costs and allowing for private-sector innovation; multiuse or reusable in-space infrastructure that allows a capability to be developed and reused over time for a variety of exploration destinations; the application of technologies for near-term applications while focusing research and development of new technologies to reduce costs, improve safety and increase mission capture over the longer term; demonstrated affordability across the project life cycle, and Near-term mission opportunities with a well-defined cadence of compelling missions providing for an incremental buildup of capabilities to perform more complex missions over time.
If NASA were to use this human-tended EML-2 waypoint, it would be the farthest humans have traveled from Earth. To make this possible, NASA has recruited a study team to create near-term missions to EML-2. The study is to be completed by March 30, 2012.
In addition, Lockheed Martin and the Lunar University Network for Astrophysics Research (LUNAR) Center are collaborating to plan an Orion mission that would go into a halo orbit of EML-2 above the
far side of the moon
. According to the LUNAR Center, EML-2 travels would take astronauts 15 percent further from Earth than Apollo astronauts and keep them in deep space nearly three times longer.
"This is extremely exciting from both the exploration and science sides," said Jack Burns, director of the LUNAR Center. "This mission concept seems to be really taking off now because it is unique and offers the prospects of doing something significant outside of low-Earth orbit within this decade."
The Christian Science Monitor
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RE: Earth observation
2/13/2012 3:06:23 PM
You don't actually put a satellite in the L2 point since it's not stable. Generally it goes in a halo orbit around the L2 point, which is what would happen in this case. It's similar to the James Webb Space Telescope at the Earth-Sun L2 point; that's in a halo orbit with a radius of 800,000km around the L2 point, and is in full sunlight all the time whereas the L2 itself is almost entirely shaded.
RE: Earth observation
2/13/2012 3:29:09 PM
The halo can't be too big though. The point of parking something at L2
that it's entirely shaded from Earth. The dream is to get a radio telescope out there (or on the surface of the far side of the moon) which can explore the universe without having to filter out all the radio noise coming from Earth.
moon orbit = 385,000 km
L2 distance from moon = 60,000 km
moon radius = 1750 km
So anything in orbit around the earth beyond 1750*(385+60)/60 = 13,000 km radius would occasionally be visible from L2. The bigger the orbit, the longer the visibility. Geosynchronous satellites are at 36,000 km, so they could communicate with something parked at L2 or thereabouts.
RE: Earth observation
2/13/2012 4:11:10 PM
Depends what you want to use it for. If you're installing a radio telescope you might want it shielded from the Earth. If it's a communications satellite, you'd want it to be visible from the Earth and the far side of the moon.
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