Saturday, September 7, 2013

LADEE Moon Probe Successfully Lifts Off

A Minotaur V rocket carrying NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) lifts off from at NASA's Wallops Flight Facility in Virginia on Friday, Sept. 6, 2013. Credit: NASA/Chris Perry

The Lunar Atmosphere and Dust Environment Explorer (LADEE) is headed toward the moon after launching at 11:27 p.m. EDT on Sept. 6 on a Minataur V rocket from Pad 0B at the Mid-Atlantic Regional Spaceport, at NASA's Wallops Flight Facility, Wallops Island, Va. Separation of the LADEE spacecraft from the rocket is confirmed. The spacecraft will arrive at the moon on October 6. LADEE is a robotic mission that will orbit the moon to gather detailed information about the lunar atmosphere, conditions near the surface and environmental influences on lunar dust. A thorough understanding of these characteristics will address long-standing unknowns, and help scientists understand other planetary bodies as well.

The probe is managed by NASA's Ames Research Center in Moffett Field, California. LADEE is doing fine, but the team is evaluating the reaction wheels at this time, looking through the data. "We're in full communication with LADEE. We know of no indication of anything wrong with reaction wheels" - said NASA's Ames Director Pete Worden.

It was a change of venue for NASA, which normally launches moon missions from Cape Canaveral, Fla. But it provided a rare light show along the East Coast for those blessed with clear skies. It was a momentous night for Wallops, which was making its first deep-space liftoff. All of its previous launches were confined to Earth orbit.

All but one of NASA's previous moon missions since 1959, including the manned Apollo flights of the late 1960s and early 1970s, originated from Cape Canaveral. The most recent were the twin Grail spacecraft launched almost exactly two years ago. The military-NASA Clementine rocketed away from Southern California in 1994.

The primary LADEE science objectives are to:

- determine the global density, composition, and measure any spatial and temporal variability of the moon's fragile atmosphere
- investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions
- characterize the lunar exospheric dust environment and variability and impacts on the lunar atmosphere
- determine the size, charge, and spatial distribution of electrostatically transported dust grains and assess their likely effects on lunar exploration and lunar-based astronomy.

The dust phenomenon has puzzled researchers for decades. Apollo astronauts saw diffuse emissions above the moon's surface. The speculation has been that this glow was caused by electrically charged dust particles being lifted from the Moon's surface by ultraviolet light from the Sun. LADEE’s remote-sensing and sampling instrumentation will test this idea.

Five sketches drawn by E. A. Cernan (Commander) of sunrise as viewed from lunar orbit during the Apollo 17 mission in 1972. Credit: NASA
Five sketches drawn by E. A. Cernan (Commander) of sunrise as viewed from lunar orbit during the Apollo 17 mission in 1972. Credit: NASA

Its programme scientist, Sarah Noble, says the mission is likely to surprise a lot of people who have been brought up to believe the Moon has no atmosphere.

“It does; it’s just it's really, really thin,” she told reporters.

“It’s so thin that the individual molecules are so few and far between that they don’t interact with each other; they never collide.

“It’s something we call an exosphere. The Earth has an exosphere as well, but you have to get out past where the International Space Station orbits before you get to this condition that we can consider an exosphere. At the Moon, it happens right at the surface.”

Photograph of LADEE's launch aboard a Minotaur V on Sept. 6, 2013. Image credit: NASA Wallops/Chris Perry
Photograph of LADEE's launch aboard a Minotaur V on Sept. 6, 2013. Image credit: NASA Wallops/Chris Perry

As $280 million probe approaches the moon it will fire its onboard propellant and be captured into lunar orbit. If this burn does not occur, LADEE will continue on a “swing-by” trajectory and escape the moon’s gravity field. The lunar orbit insertion burn for the spacecraft lasts approximately three minutes and changes the orbiter velocity enough to capture the spacecraft around the moon.

During the 100-day Science Phase, the moon will rotate more than three times underneath the LADEE orbit. The LADEE spacecraft and payload instruments are designed to orbit the moon in an upright posture; that is, with the longitudinal spin axis pointing north. This upright cruise attitude is intended to place the antenna in the best location for communication with Earth, and will allow exposure to the sun similar to power and thermal conditions in lunar orbit. Depending on antenna placement and signal strength, LADEE's rotation may need to be halted to perform communications with Earth stations.

LADEE launch. Credit: Charlie Loyd
LADEE launch. Credit: Charlie Loyd

The design of the LADEE science orbit is such that, when the onboard propellant is almost gone at the end of the Science Phase, LADEE's orbit will be managed down to lower altitudes until it impacts the lunar surface. LADEE will continue to acquire data until impact. It is unlikely there will be any attitude requirements during decommissioning, except perhaps keeping the antenna pointed at the Earth for telemetry and tracking until the last orbit. There are no plans to target the impact points on the lunar surface. If LADEE's propellant is depleted and orbital decay occurs naturally, the point of impact may not be in sight of Earth.

The 844-pound spacecraft has three science instruments as well as laser communication test equipment that could revolutionize data relay. NASA hopes to eventually replace its traditional radio systems with laser communications, which would mean faster bandwidth using significantly less power and smaller devices.

Artist's concept of LADEE spacecraft approaching the moon. Credit: NASA
Artist's concept of LADEE spacecraft approaching the moon. Credit: NASA

"There's no question that as we send humans farther out into the solar system, certainly to Mars," that laser communications will be needed to send high-definition and 3-D video, said NASA's science mission chief, John Grunsfeld, a former astronaut who worked on the Hubble Space Telescope.

Credit: NASABBCHuffington Post

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