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  NASA's LADEE to study the moon's atmosphere

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Author Topic:   NASA's LADEE to study the moon's atmosphere
Robert Pearlman
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NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE)

NASA's Lunar Atmosphere and Dust Environment Explorer (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. An understanding of these characteristics will address long-standing unknowns, and help scientists understand other planetary bodies as well.

The LADEE spacecraft's modular common spacecraft bus, or body, is an innovative way of transitioning away from custom designs and toward multi-use designs and assembly-line production, which could drastically reduce the cost of spacecraft development, just as the Ford Model T did for automobiles.

LADEE will launch from the Mid Atlantic Regional Spaceport's (MARS) Pad 0B at NASA's Wallops Flight Facility on a U.S. Air Force Minotaur V rocket, an excess ballistic missile converted into a space launch vehicle and operated by Orbital Sciences Corporation. This will be the first flight of the Minotaur V and the first launch beyond Earth orbit from Wallops.

Linda Voss
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NASA release (June 4, 2013)
LADEE Arrives at Wallops for Moon Mission

The NASA Lunar Atmosphere and Dust Environment Explorer arrived [June 4] at NASA's Wallops Flight Facility to begin final processing for its trip to the moon later this year.

Linda Voss
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NASA release (July 11, 2013)
LADEE Journeys to its Launch Facility

After safely arriving at Wallops Flight Facility, technicians removed LADEE from the shipping container and placed it in a clean room, where it will stay until ready to roll out to the launch pad.

LADEE was tested to make sure nothing was damaged during the transport, then engineers conducted a final radio communications compatibility test. To perform this test, engineers brought the same equipment used in previous tests to Wallops and connected it to the spacecraft to exercise the communications modes that will be used during the mission.

LADEE is going through final preparation and close-out in advance of fueling and being encapsulated by Orbital Sciences Corp., in the fairing of the U.S. Air Force's Minotaur V launch vehicle.

One important preparation is spin-balancing LADEE. During this procedure, the spacecraft is mounted to a spin table and rotated at a high-speed to make sure it is perfectly balanced for launch. The observatory will be spin-balanced dry, then fueled, and then spun again after fueling.

At that point the LADEE Observatory will be ready to be encapsulated in the launch vehicle fairing and rolled out to Mid-Atlantic Regional Spaceport’s launch pad to be mated to the launch vehicle stack.

Robert Pearlman
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NASA release
New Moon Mission to Launch at NASA's Wallops

NASA's LADEE is scheduled to launch Friday, Sept. 6, 2013 at 11:27 p.m. EDT (0327 GMT Sept. 7). Backup launch days are Sept. 7-10.

LADEE will launch from the Mid Atlantic Regional Spaceport's (MARS) Pad 0B on a U.S. Air Force Minotaur V rocket, an excess ballistic missile converted in to a space launch vehicle and operated by Orbital. This will be the first flight of the Minotaur V and the first launch beyond Earth orbit from Wallops.

Robert Pearlman
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NASA release
NASA Prepares for First Virginia Coast Launch to Moon

In an attempt to answer prevailing questions about our moon, NASA is making final preparations to launch a probe at 11:27 p.m. EDT Friday, Sept. 6 (0327 GMT Sept. 7), from NASA's Wallops Flight Facility on Wallops Island, Va.

The small car-sized Lunar Atmosphere and Dust Environment Explorer (LADEE) is a robotic mission that will orbit the moon to gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky. A thorough understanding of these characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury, and the moons of outer planets.

"The moon's tenuous atmosphere may be more common in the solar system than we thought," said John Grunsfeld, NASA's associate administrator for science in Washington. "Further understanding of the moon's atmosphere may also help us better understand our diverse solar system and its evolution."

The mission has many firsts, including the first flight of the Minotaur V rocket, testing of a high-data-rate laser communication system, and the first launch beyond Earth orbit from the agency's Virginia Space Coast launch facility.

LADEE also is the first spacecraft designed, developed, built, integrated and tested at NASA's Ames Research Center in Moffett Field, Calif. The probe will launch on a U.S. Air Force Minotaur V rocket, an excess ballistic missile converted into a space launch vehicle and operated by Orbital Sciences Corp. of Dulles, Va.

LADEE was built using an Ames-developed Modular Common Spacecraft Bus architecture, a general purpose spacecraft design that allows NASA to develop, assemble and test multiple modules at the same time. The LADEE bus structure is made of a lightweight carbon composite with a mass of 547.2 pounds -- 844.4 pounds when fully fueled.

"This mission will put the common bus design to the test," said Ames Director S. Pete Worden. "This same common bus can be used on future missions to explore other destinations, including voyages to orbit and land on the moon, low-Earth orbit, and near-Earth objects."

Butler Hine, LADEE project manager at Ames, said the innovative common bus concept brings NASA a step closer to multi-use designs and assembly line production and away from custom design. "The LADEE mission demonstrates how it is possible to build a first class spacecraft at a reduced cost while using a more efficient manufacturing and assembly process," Hine said.

Approximately one month after launch, LADEE will begin its 40-day commissioning phase, the first 30 days of which the spacecraft will be performing activities high above the moon's surface. These activities include testing a high-data-rate laser communication system that will enable higher rates of satellite communications similar in capability to high-speed fiber optic networks on Earth.

After commissioning, LADEE will begin a 100-day science phase to collect data using three instruments to determine the composition of the thin lunar atmosphere and remotely sense lofted dust, measure variations in the chemical composition of the atmosphere, and collect and analyze samples of any lunar dust particles in the atmosphere. Using this set of instruments, scientists hope to address a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow above the lunar horizon detected during several Apollo missions?

After launch, Ames will serve as a base for mission operations and real-time control of the probe. NASA's Goddard Space Flight Center in Greenbelt, Md., will catalogue and distribute data to a science team located across the country.

Robert Pearlman
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NASA release
Project Manager Update: LADEE Ready for Launch

Engineers from NASA's Ames Research Center in Moffett Field, Calif., have successfully completed launch preparation activities for NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) observatory, which has been encapsulated into the nose-cone of the Minotaur V rocket at NASA's Wallops Flight Facility in Virginia.

LADEE now is ready to launch when the window opens on Sept. 6, 2013.

Above: A wide-angle view of an inert Minotaur V launch vehicle is erected on the Mid-Atlantic Regional Spaceport's pad 0B at NASA's Wallops Flight Facility in Virginia during a pathfinder exercise for NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission. Credit: NASA Wallops/Jackie Adkins

After safely arriving at NASA Wallops in June, the LADEE observatory went through final preparations and close-outs, which included checking the spacecraft's alignment after its cross-country shipment, checking the propulsion system for leaks, inspecting and repairing solar panels, and final electrical tests.

After all of the activities were completed, it was time to start some of the scarier more challenging portions of the launch preparations: spin testing and fueling.

To make sure that the spacecraft is perfectly balanced for flight, engineers mount it onto a spin table and rotate it at high speeds, approximately one revolution per second. The team measures any offsets during the spinning, and then adds small weights to the spacecraft to balance it.

Once the spacecraft was balanced dry, we then loaded the propulsion tanks with fuel, oxidizer, and pressurant. The spin testing was performed again "wet," or with fuel, in order to see if the balance changed with the full fuel tanks. The final wet spin balance went very well.

Above: Engineers as NASA's Wallops Flight Facility in Virginia encapsule the LADEE spacecraft into the fairing of the Minotaur V launch vehicle nose-cone. Credit: NASA Wallops/Terry Zaperach

The next step was to lift the LADEE spacecraft onto the fifth stage — or the top — of the rocket, and then spin that whole stack in order to balance it for when the fifth stage burns during the ascent. Before and after this spin balancing, various explosive charges were installed onto the spacecraft and fifth stage, which will be used during flight to enable the propulsion system and remove the cover of one of the science instruments. The combination of propellents, explosives, and spinning made all of this activity pretty challenging.

After all of that was accomplished, engineers mounted the LADEE observatory onto the fifth stage rocket motor and encapsulated it in the nose-cone — or fairing — of the United States Air Force's Minotaur V launch vehicle, operated by Orbital Sciences Corp., Dulles, Va. It was then hooked up to an environmental control system that will keep clean, dry, cool gas flowing into the fairing.

After everything was ready, the combined LADEE and fifth stage motor in the fairing was moved from the clean room it had lived in all summer, out to the launch pad, and lifted on top of the rocket stack, with the first through fourth stages already in place.

Above: NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft sits in the nose-cone at the top of the full Minotaur V launch vehicle stack. Credit: NASA Ames/Zion Young

We are now ready for launch when the window opens on Sept. 6.

Robert Pearlman
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collectSPACE
To the moon, via Virginia: NASA's LADEE lifts off to study lunar atmosphere

NASA's first moon-bound probe to launch from Virginia lifted off late Friday evening (Sept. 6) on the maiden flight of a new five-stage rocket.

The Lunar Atmosphere and Dust Environment Explorer, or LADEE (pronounced "laddie") soared space-ward at 11:27 p.m. EDT (0327 GMT Sept. 7) riding atop Orbital Sciences Corp.'s new Minotaur V booster, a converted Peacekeeper missile, from the Mid-Atlantic Regional Spaceport Pad 0B at NASA's Wallops Flight Facility on Wallops Island, Va.

The $280 million LADEE mission will use a trio of science instruments to study the moon's exosphere, the very thin layer of atmosphere just above the lunar surface, and the effects that environment may have on moon dust.

Robert Pearlman
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NASA release
Sept. 7, 3:40 a.m. EDT Update

NASA has confirmed its Lunar Atmosphere and Dust Environment Explorer (LADEE) has separated from its ride into space, powered up and is communicating with ground controllers following a successful launch at 11:27 p.m. EDT Friday, Sept. 6, from the agency's Wallops Flight Facility in Virginia. LADEE is on its way to arrive at the moon in 30 days, then enter lunar orbit.

According to the LADEE mission operations team at NASA's Ames Research Center in Moffett Field, Calif., during technical checkouts the LADEE spacecraft commanded itself to shut down the reaction wheels used to position and stabilize the spacecraft.

"The LADEE spacecraft is working as it was designed to under these conditions – there's no indication of anything wrong with the reaction wheels or spacecraft," said S. Pete Worden, Ames center director. "The LADEE spacecraft is communicating and is very robust. The mission team has ample time to resolve this issue before the spacecraft reaches lunar orbit. We don't have to do anything in a rush."

LADEE team members are currently analyzing the situation. Normal checkout takes a couple of days, and this anomaly may add a couple more days to the process.

"This is not an unusual event in spacecraft," Worden said. "We plan in the next few days to complete spacecraft checkout."

Robert Pearlman
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NASA release
Sept. 7, 1:40 p.m. EDT Update

NASA has confirmed the reaction wheels of its Lunar Atmosphere and Dust Environment Explorer (LADEE) were successfully brought back on-line and the spacecraft has acquired its safe-mode attitude profile.

Last night during technical checkouts the LADEE spacecraft commanded itself to shut down the reaction wheels used to position and stabilize the spacecraft. According to the LADEE mission operations team at NASA's Ames Research Center in Moffett Field, Calif., this was determined to be the result of fault protection limits put in place prior to launch to safeguard the reaction wheels. The limits that caused the powering off of the wheels soon after activation were disabled, and reaction wheel fault protection has been selectively re-enabled.

"Our engineers will determine the appropriate means of managing the reaction wheel fault protection program. Answers will be developed over time and will not hold up checkout activities," said Butler Hine, LADEE project manager.

"The initial checkout flight procedure is progressing," said S. Pete Worden, Ames center director. "The reaction wheel issue noted soon after launched was resolved a few hours later. The LADEE spacecraft is healthy and communicating with mission operators."

Robert Pearlman
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LADEE enters lunar orbit

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) entered orbit around the moon on Sunday morning (Oct. 6), a month after launching to study the lunar exosphere.

The probe performed a successful four-minute lunar orbit insertion burn beginning at 5:57 a.m. CDT (1057 GMT), allowing it be captured by the moon's gravity in a retrograde equatorial lunar orbit.

Robert Pearlman
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NASA release
NASA Spacecraft Begins Collecting Lunar Atmosphere Data

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) is ready to begin collecting science data about the moon.

On Nov. 20, the spacecraft successfully entered its planned orbit around the moon's equator -- a unique position allowing the small probe to make frequent passes from lunar day to lunar night. This will provide a full scope of the changes and processes occurring within the moon's tenuous atmosphere.

LADEE now orbits the moon about every two hours at an altitude of eight to 37 miles (12-60 kilometers) above the moon's surface. For about 100 days, the spacecraft will gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky.

"A thorough understanding of the characteristics of our lunar neighbor will help researchers understand other small bodies in the solar system, such as asteroids, Mercury, and the moons of outer planets," said Sarah Noble, LADEE program scientist at NASA Headquarters in Washington.

Scientists also will be able to study the conditions in the atmosphere during lunar sunrise and sunset, where previous crewed and robotic missions detected a mysterious glow of rays and streamers reaching high into the lunar sky.

On Nov. 20, flight controllers in the LADEE Mission Operations Center at NASA's Ames Research Center in Moffett Field, Calif., confirmed LADEE performed a crucial burn of its orbit control system to lower the spacecraft into its optimal position to enable science collection. Mission managers will continuously monitor the spacecraft's altitude and make adjustments as necessary.

"Due to the lumpiness of the moon's gravitational field, LADEE's orbit requires significant maintenance activity with maneuvers taking place as often as every three to five days, or as infrequently as once every two weeks," said Butler Hine, LADEE project manager at Ames. "LADEE will perform regular orbital maintenance maneuvers to keep the spacecraft’s altitude within a safe range above the surface that maximizes the science return."

In addition to science instruments, the spacecraft carried the Lunar Laser Communications Demonstration, NASA's first high-data-rate laser communication system. It is designed to enable satellite communication at rates similar to those of high-speed fiber optic networks on Earth. The system was tested successfully during the commissioning phase of the mission, while LADEE was still at a higher altitude.

Robert Pearlman
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NASA release
NASA Extends Moon Exploring Satellite Mission

NASA's Lunar Atmosphere and Dust Environment Explorer, or LADEE, observatory has been approved for a 28-day mission extension. The spacecraft is now expected to impact the lunar surface on or around April 21, 2014, depending on the final trajectory.

The extension provides an opportunity for the satellite to gather an additional full lunar cycle worth of very low-altitude data to help scientists unravel the mysteries of the moon’s atmosphere.

"The launch vehicle performance and orbit capture burns using LADEE's onboard engines were extremely accurate, so the spacecraft had significant propellant remaining to enable extra science," said Butler Hine, LADEE project manager at NASA’s Ames Research Center in Moffett Field, Calif., where the mission was designed, built, tested and its day-to-day operations are managed. "This extension represents a tremendous increase in the amount of science data returned from the mission."

The small, car-sized robotic probe launched Sept. 6, 2013, from NASA's Wallops Flight Facility on Wallops Island, Va., and has been orbiting the moon since Oct. 6. On Nov. 10, LADEE began gathering science data and on Nov. 20, the spacecraft entered its science orbit around the moon's equator at an altitude of eight to 37 miles (12-60 kilometers) above the surface; a unique position that allows the spacecraft to frequently pass from lunar day to lunar night, approximately every two hours. This vantage provides data about the full scope of changes and processes occurring within the moon's tenuous atmosphere.

"The science team has already established a baseline of data for the tenuous lunar atmosphere, or exosphere, and dust impacts," said Rick Elphic LADEE project scientist at Ames. "One cool thing about this extension is that we plan to fly LADEE at only a few kilometers above the lunar surface. This will be much lower than we’ve been before."

Using a set of three instruments, scientists are able to measure the chemical composition of the atmosphere, collect and analyze samples of lunar dust particles in the atmosphere and hope to address a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow above the lunar horizon detected during several Apollo missions?

Specifically, the Neutral Mass Spectrometer operates while pointing in different directions to look for atoms and molecules in the lunar atmosphere from a variety of sources, and has measured helium, neon, and argon-40; three noble gases. The Ultraviolet-Visible Spectrometer has peered over the lunar horizon to look for the glow of atoms, molecules and dust in the lunar atmosphere and has made measurements of atmospheric sodium and potassium at lunar sunset, sunrise and noon. The Lunar Dust Experiment (LDEX) recorded dust impacts as soon as its cover opened and has measured the dust tossed up by a fairly steady "rain" of meteoroids on the lunar surface. LDEX occasionally sees an increase in dust impacts due to meteoroid showers, such as the Geminids, and "dust bursts" that may be due to LADEE flying through plumes kicked up from nearby meteoroid impacts.

Detailed information about the structure and composition of the thin lunar atmosphere and whether dust is being lofted into the lunar sky will help researchers understand other bodies in the solar system, such as large asteroids, Mercury and the moons of outer planets.

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NASA release
LADEE Sends Its First Images of the Moon Back to Earth

Earlier this month, NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) observatory successfully downlinked images of the moon and stars taken by onboard camera systems, known as star trackers. This is the first time the LADEE team commanded the spacecraft to send these pictures back to Earth.

The main job of a star tracker is to snap images of the surrounding star field so that the spacecraft can internally calculate its orientation in space. It completes this task many times per minute. The accuracy of each of LADEE's instruments' measurements depends on the star tracker calculating the precise orientation of the spacecraft.

Above: Series of LADEE star tracker images features the lunar terrain. (Credit: NASA Ames)

"Star tracker cameras are actually not very good at taking ordinary images," said Butler Hine LADEE project manager at NASA's Ames Research Center in Moffett Field, Calif. "But they can sometimes provide exciting glimpses of the lunar terrain."

Given the critical nature of its assignment, a star tracker doesn't use ordinary cameras. Star trackers' lenses have a wide-angle field of view in order to capture the night sky in a single frame.

The images shown here were acquired on Feb. 8, 2014, around 23:45 UTC, while LADEE was carrying out atmospheric measurements. The series of five images were taken at one-minute intervals, and caught features in the northern western hemisphere of the moon. LADEE was traveling approximately 60 miles (100 km) per minute along its orbit. All images were taken during lunar night, but with Earthshine illuminating the surface.

The initial image captured the smooth-floored crater Krieger, about 14 miles (23 km) in diameter, on the horizon, with four mile (seven km) wide Toscanelli, in the foreground.

The second image shows Wollaston P, about two-and-a-half miles (4 km) diameter, near the horizon, and the southeastern flank of the lunar mountain Mons Herodotus.

The third image caught a minor lunar mountain range, Montes Agricola, which is northwest of the large bright crater Aristarchus (out of view), as well as the flat-floored crater Raman, about six miles (10 km) diameter.

Image four in the series captures Golgi, about four miles (6 km) in diameter, and three-mile-wide (5 km) Zinner.

The final image views craters Lichtenberg A and Schiaparelli E in the smooth mare basalt plains of Western Oceanus Procellarum, west of the Aristarchus plateau.

The star trackers will operate while LADEE continues to measure the chemical composition of the atmosphere, collect and analyze samples of lunar dust particles in the atmosphere and hope to address a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow above the lunar horizon observed during several Apollo missions? And who knows? The star trackers may help answer that question.

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NASA release
NASA Satellite to Continue Gathering Data Up to Planned Lunar Impact

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is gradually lowering its orbital altitude to continue making science observations prior to its planned impact on the moon’s surface on or before April 21.

Ground controllers at NASA's Ames Research Center in Moffett Field, Calif., are maneuvering the spacecraft to fly approximately 1 to 2 miles (2 to 3 kilometers) above the lunar surface to gather science measurements at the lowest altitude possible.

A final maneuver will ensure LADEE's trajectory will impact the far side of the moon, which is not in view of Earth or near any previous lunar mission landings. Ground controllers have little room for error with LADEE's navigation system, and at these low orbital altitudes, a small error could mean the difference between continuing to orbit above the lunar surface and impacting it. Because of this, the team does not intend to target a specific impact location on the moon's surface.

"The moon's gravity field is so lumpy, and the terrain is so highly variable with crater ridges and valleys that frequent maneuvers are required or the LADEE spacecraft will impact the moon’s surface," said Butler Hine, LADEE project manager at Ames. "Even if we perform all maneuvers perfectly, there's still a chance LADEE could impact the moon sometime before April 21, which is when we expect LADEE's orbit to naturally decay after using all the fuel onboard."

Until mid-April, ground controllers will continue to fire the LADEE altitude control thrusters once a week to keep the observatory in its target orbit. On April 11, LADEE will perform its final orbital maintenance maneuver before the total lunar eclipse on April 15, when Earth’s shadow passes over the Moon. This eclipse, which will last approximately four hours, exposes the spacecraft to conditions at the limits of what it was designed to withstand.

"If LADEE survives the eclipse, we will have nearly a week of additional science at low altitudes before impact," said Rick Elphic, LADEE project scientist at Ames. "For a short mission like LADEE, even a few days count for a lot – this is a very exciting time in the mission."

After the eclipse, ground controllers will determine how well the spacecraft is functioning. If it is healthy, LADEE will continue to acquire and transmit science data, as longs as its altitude and contact with ground controllers allow.

"We're very eager to see how LADEE handles the prolonged exposure to the intense cold of this eclipse, and we've used flight data to predict that most of the spacecraft should be fine," said Hine. "However, the eclipse will really put the spacecraft design through an extreme test, especially the propulsion system."

Launched in September 2013, from NASA's Wallops Flight Facility on Wallops Island, Va., the vending-machine size spacecraft has been orbiting the moon since Oct. 6. On Nov. 10, LADEE began gathering science data, and on Nov. 20, the spacecraft entered its science orbit around the moon's equator. LADEE has been in extended mission operations following a highly successful 100-day primary science phase.

"Because the LADEE team has flawlessly performed every maintenance maneuver, they've been able to keep the spacecraft flying in its proper orbit and have enabled this amazing mission extension and science to continue up until the very end," said Joan Salute, LADEE program executive at NASA Headquarters in Washington.

LADEE's three science payload instruments have been working to unravel the mysteries of the moon's atmosphere, acquiring more than 700,000 measurements. In its previous orbit, LADEE's closest approach to the lunar surface was between 12.5 and 31 miles (20 and 50 kilometers), and its farthest was between 47 and 93 miles (75 and 150 kilometers) – a unique position that allows the spacecraft to frequently pass from lunar day to lunar night every two hours. This vantage provides data on the full range of changes and processes occurring within the moon's tenuous atmosphere.

Scientists hope this data will help answer a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow detected during several Apollo missions above the lunar horizon? LADEE also is gathering detailed information about the structure and composition of the thin lunar atmosphere. A thorough understanding of these characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury, and the moons of outer planets.

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NASA release
NASA completes LADEE mission with planned impact on moon's surface

Ground controllers at NASA's Ames Research Center in Moffett Field, Calif., have confirmed that NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft impacted the surface of the moon, as planned, between 9:30 and 10:22 p.m. PDT Thursday, April 17 (12:30 and 1:22 a.m. EDT or 0430 and 0522 GMT, April 18).

LADEE lacked fuel to maintain a long-term lunar orbit or continue science operations and was intentionally sent into the lunar surface. The spacecraft's orbit naturally decayed following the mission's final low-altitude science phase.

During impact, engineers believe the LADEE spacecraft, the size of a vending machine, broke apart, with most of the spacecraft's material heating up several hundred degrees — or even vaporizing — at the surface. Any material that remained is likely buried in shallow craters.

"At the time of impact, LADEE was traveling at a speed of 3,600 miles per hour — about three times the speed of a high-powered rifle bullet," said Rick Elphic, LADEE project scientist at Ames. "There's nothing gentle about impact at these speeds — it's just a question of whether LADEE made a localized craterlet on a hillside or scattered debris across a flat area. It will be interesting to see what kind of feature LADEE has created."

In early April, the spacecraft was commanded to carry out maneuvers that would lower its closest approach to the lunar surface. The new orbit brought LADEE to altitudes below one mile (two kilometers) above the lunar surface. This is lower than most commercial airliners fly above Earth, enabling scientists to gather unprecedented science measurements.

On April 11, LADEE performed a final maneuver to ensure a trajectory that caused the spacecraft to impact the far side of the moon, which is not in view of Earth or near any previous lunar mission landings. LADEE also survived the total lunar eclipse on April 14 to 15. This demonstrated the spacecraft's ability to endure low temperatures and a drain on batteries as it, and the moon, passed through Earth's deep shadow.

In the coming months, mission controllers will determine the exact time and location of LADEE's impact and work with the agency's Lunar Reconnaissance Orbiter (LRO) team to possibly capture an image of the impact site. Launched in June 2009, LRO provides data and detailed images of the lunar surface.

"It's bittersweet knowing we have received the final transmission from the LADEE spacecraft after spending years building it in-house at Ames, and then being in constant contact as it circled the moon for the last several months," said Butler Hine, LADEE project manager at Ames.

Launched in September 2013 from NASA's Wallops Flight Facility in Virginia, LADEE began orbiting the moon Oct. 6 and gathering science data Nov. 10. The spacecraft entered its science orbit around the moon's equator on Nov. 20, and in March 2014, LADEE extended its mission operations following a highly successful 100-day primary science phase.

LADEE also hosted NASA's first dedicated system for two-way communication using laser instead of radio waves. The Lunar Laser Communication Demonstration (LLCD) made history using a pulsed laser beam to transmit data over the 239,000 miles from the moon to the Earth at a record-breaking download rate of 622 megabits-per-second (Mbps). In addition, an error-free data upload rate of 20 Mbps was transmitted from the primary ground station in New Mexico to the Laser Communications Space Terminal aboard LADEE.

LADEE gathered detailed information about the structure and composition of the thin lunar atmosphere. In addition, scientists hope to use the data to address a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow seen above the lunar horizon during several Apollo missions?

"LADEE was a mission of firsts, achieving yet another first by successfully flying more than 100 orbits at extremely low altitudes," said Joan Salute, LADEE program executive, at NASA Headquarters in Washington. "Although a risky decision, we're already seeing evidence that the risk was worth taking."

A thorough understanding of the characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury and the moons of outer planets.

NASA also included the public in the final chapter of the LADEE story. A "Take the Plunge" contest provided an opportunity for the public to guess the date and time of the spacecraft's impact via the internet. Thousands submitted predictions. NASA will provide winners a digital congratulatory certificate.

See here for discussion of NASA's LADEE lunar atmosphere moon mission.

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