Image: The twin Gravity Recovery and Interior Laboratory (GRAIL) spacecraft
Alan Walters/
The twin Gravity Recovery and Interior Laboratory (GRAIL) spacecraft are mirror images of one another. The probes will orbit the moon and take detailed measurements of the lunar gravity field.
updated 8/14/2011 11:08:07 AM ET 2011-08-14T15:08:07

A set of twin lunar probes are gearing up for a planned September launch to the moon, with NASA set to attach the spacecraft duo to their rocket soon.

The twin Gravity Recovery and Interior Laboratory spacecraft (nicknamed GRAIL) are poised to launch moonward on Sept. 8 from the Cape Canaveral Air Force Base here.

The GRAIL mission is designed to discover details of the moon's gravity field from the inside out. The twin probes will fly in tandem to scan the lunar crust to the core, in hopes of collecting measurements for the most accurate gravitational map of the moon ever produced.

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"Unlike many other planetary missions GRAIL consists of two spacecraft which are mirror images of one another," said Sami Asmar a member of the GRAIL science team. "So they cannot be interchanged or switched and they will fly together in formation transmitting radio information between the two spacecraft – this allows us to peer into the moon from the core to the crust." [ Photos: Our Changing Moon ]

Cleaning up for the moon
The GRAIL probes are currently being housed in a clean room near NASA's Kennedy Space Center here. Anyone who enters the ultra-clean facility is required to wear a protective white jumpsuit, sometimes referred to as a "bunny suit."

This head-to-toe outer layer leaves only the eyes exposed, but it is just the first precautionary tier in a multi-layered system designed to keep the spacecraft clean before it is sent to our nearest celestial neighbor.

All camera equipment brought in to photograph the twin GRAIL spacecraft must be cleaned under the supervision of specially trained contamination-control specialists, and strict rules govern what type of equipment can be brought into the facility. These regulations extend even to pens and paper — no conventional writing utensils are allowed inside the clean room, since ordinary paper can carry particles that could clog vital systems on the spacecraft in the microgravity environment of space.

Shoot for the moon
Grail is slated to launch from Launch Complex 17-B at Cape Canaveral Air Force Station on Sept. 8 at 8:37 a.m. EDT (1237 GMT). The two probes will ride on a Delta 2 rocket, in what will be the final launch of a Delta 2 from the Air Force-run spaceport.

After the probes lift off, the journey to the moon will last about 3 1/2 months. After that, the science mission is set to last for a total of 90 days. GRAIL is similar to the Gravity Recovery and Climate Experiment or GRACE mission which launched in 2002 and made detailed measurements of Earth's gravity field. [ Infographic: Inside Earth's Moon ]

"GRAIL will have a trans-lunar cruise of about three-and-a-half months, they will arrive at the moon on New Year’s Eve 2012," said Bruce Reid, the mission's launch service provider manager.  "Once there they will completely map the gravity of the moon. This is important for not only future missions, but to also provide us with a better understanding other terrestrial planets.”

The GRAIL science team is made up of a number of scientists, including former NASA astronaut Sally Ride, who is assisting with the project’s public outreach efforts.

GRAIL is the second of three NASA missions launching over the next few months to explore the solar system.

On Aug. 5, NASA launched the Juno spacecraft toward Jupiter. It will take the probe five years to reach the gas giant planet.

NASA's newest Mars rover, the Mars Science Laboratory Curiosity, is currently scheduled to launch in late November.

Follow for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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