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Ebb and Flow's Final Moments

These side-by-side, 3-D comparisons depict the unnamed lunar mountain targeted by the NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission for controlled impact of They also include the ground tracks the spacecraft are expected to follow into the lunar terrain. These graphics were generated using data from the Lunar Orbiter Laser Altimeter instrument aboard NASA's Lunar Reconnaissance Orbiter spacecraft.

On the left is the mountain with the ground track and mission termination point for the Ebb spacecraft. On the right is the mountain, ground track and mission termination point for the Flow spacecraft.

Image credit: NASA/JPL-Caltech/MIT/GSFC

PASADENA, Calif. -- Twin lunar-orbiting NASA spacecraft that have allowed scientists to learn more about the internal structure and composition of the moon are being prepared for their controlled descent and impact on a mountain near the moon's north pole at about 2:28 p.m. PST (5:28 p.m. EST) Monday, Dec. 17.

Ebb and Flow, the Gravity Recovery and Interior Laboratory (GRAIL) mission probes, are being sent purposely into the lunar surface because their low orbit and low fuel levels preclude further scientific operations. The duo's successful prime and extended science missions generated the highest-resolution gravity field map of any celestial body. The map will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved.

"It is going to be difficult to say goodbye," said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "Our little robotic twins have been exemplary members of the GRAIL family, and planetary science has advanced in a major way because of their contributions."

The mountain where the two spacecraft will make contact is located near a crater named Goldschmidt. Both spacecraft have been flying in formation around the moon since Jan. 1, 2012. They were named by elementary school students in Bozeman, Mont., who won a contest. The first probe to reach the moon, Ebb, also will be the first to go down, at 2:28:40 p.m. PST. Flow will follow Ebb about 20 seconds later.

Both spacecraft will hit the surface at 3,760 mph (1.7 kilometers per second). No imagery of the impact is expected because the region will be in shadow at the time.

Ebb and Flow will conduct one final experiment before their mission ends. They will fire their main engines until their propellant tanks are empty to determine precisely the amount of fuel remaining in their tanks. This will help NASA engineers validate fuel consumption computer models to improve predictions of fuel needs for future missions.

"Our lunar twins may be in the twilight of their operational lives, but one thing is for sure, they are going down swinging," said GRAIL project manager David Lehman of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Even during the last half of their last orbit, we are going to do an engineering experiment that could help future missions operate more efficiently."

Because the exact amount of fuel remaining aboard each spacecraft is unknown, mission navigators and engineers designed the depletion burn to allow the probes to descend gradually for several hours and skim the surface of the moon until the elevated terrain of the target mountain gets in their way.

The burn that will change the spacecrafts' orbit and ensure the impact is scheduled to take place Friday morning, Dec. 14.

"Such a unique end-of-mission scenario requires extensive and detailed mission planning and navigation," said Lehman. "We've had our share of challenges during this mission and always come through in flying colors, but nobody I know around here has ever flown into a moon mountain before. It'll be a first for us, that's for sure."

During their prime mission, from March through May, Ebb and Flow collected data while orbiting at an average altitude of 34 miles (55 kilometers). Their altitude was lowered to 14 miles (23 kilometers) for their extended mission, which began Aug. 30 and sometimes placed them within a few miles of the moon's tallest surface features.

JPL manages the GRAIL mission for NASA's Science Mission Directorate in Washington. The mission is part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems in Denver built the spacecraft. JPL is a division of the California Institute of Technology in Pasadena.

For more information about GRAIL, visit: http://www.nasa.gov/grail .

DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov

Sarah McDonnell 617-253-8923
Massachusetts Institute of Technology, Cambridge
s_mcd@mit.edu

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

miércoles, 12 de diciembre de 2012

NASA - NASA's GRAIL Creates Most Accurate Moon Gravity Map

NASA to Host Dec.13 Teleconference on Twin Probes Mission Ending Moon Impact

PASADENA, Calif. -- NASA will host a media teleconference at 10:30 a.m. PST (1:30 p.m. EST) Thursday, Dec. 13, to provide an overview of events leading up to twin spacecraft being commanded to impact the moon's surface on Dec. 17 at approximately 2:28 p.m.

NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, whose two washing machine-sized probes were named Ebb and Flow by elementary school students in Bozeman, Montana, via a nationwide contest, have successfully completed their prime missions and have only days to go on their extended mission science collection. As planned, the duo is running low on fuel. They have been orbiting the moon since New Year's Eve and New Year's Day, respectively, giving scientists unprecedented detail about the moon's internal structure and composition.

For teleconference dial-in information, reporters must send their name, media affiliation and telephone number to Elena Mejia at elena.mejia@jpl.nasa.gov or call NASA's Jet Propulsion Laboratory Media Relations Office at 818-354-5011.

Audio and visuals of the event will be streamed live online at:

http://www.nasa.gov/newsaudio

and

www.ustream.tv/nasajpl

For more information about the mission, visit:

http://www.nasa.gov/grail

This movie shows the variations in the lunar gravity field as measured by NASA's Gravity Recovery and Interior Laboratory (GRAIL) during the primary mapping mission from March to May 2012. Very precise microwave measurements between two spacecraft, named Ebb and Flow, were used to map gravity with high precision and high spatial resolution. › Download video › Image gallery

This image depicting the porosity of the lunar highland crust was derived using bulk density data from NASA's GRAIL mission and independent grain density measurements from NASA's Apollo moon mission samples as well as orbital remote-sensing data.

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Closer Look at Lunar Highland Crust

This image depicting the porosity of the lunar highland crust was derived using bulk density data from NASA's GRAIL mission and independent grain density measurements from NASA's Apollo moon mission samples as well as orbital remote-sensing data. Red corresponds to higher than average porosities and blue corresponds to lower than average porosities. White denotes regions that contain mare basalts (thin lines) and that were not analyzed.

The 12 percent average porosity of the highland crust is a consequence of fractures generated by billions of years of impact cratering. The crustal porosities in the interiors of many impact basins are lower than their surroundings, a result of high temperatures experienced at the time of crater formation. In contrast, the porosities immediately exterior to many impact basins are higher than average as a result of fracturing by impact-generated shock waves and the deposition of impact ejecta.

Image Credit: NASA/JPL-Caltech/ IPGP

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GRAIL's Gravity Field of the Moon

This map shows the gravity field of the moon as measured by NASA's GRAIL mission. The viewing perspective, known as a Mercator projection, shows the far side of the moon in the center and the nearside (as viewed from Earth) at either side.

Units are milliGalileos where 1 Galileo is 1 centimeter per second squared. Reds correspond to mass excesses which create areas of higher local gravity, and blues correspond to mass deficits which create areas of lower local gravity.

Image credit: NASA/ARC/MIT

PASADENA, Calif. -- Twin NASA probes orbiting Earth's moon have generated the highest resolution gravity field map of any celestial body.

The new map, created by the Gravity Recovery and Interior Laboratory (GRAIL) mission, is allowing scientists to learn about the moon's internal structure and composition in unprecedented detail. Data from the two washing machine-sized spacecraft also will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved.

The gravity field map reveals an abundance of features never before seen in detail, such as tectonic structures, volcanic landforms, basin rings, crater central peaks and numerous simple, bowl-shaped craters. Data also show the moon's gravity field is unlike that of any terrestrial planet in our solar system.

These are the first scientific results from the prime phase of the mission, and they are published in three papers in the journal Science.

"What this map tells us is that more than any other celestial body we know of, the moon wears its gravity field on its sleeve," said GRAIL Principal Investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "When we see a notable change in the gravity field, we can sync up this change with surface topography features such as craters, rilles or mountains."

According to Zuber, the moon's gravity field preserves the record of impact bombardment that characterized all terrestrial planetary bodies and reveals evidence for fracturing of the interior extending to the deep crust and possibly the mantle. This impact record is preserved, and now precisely measured, on the moon.

The probes revealed the bulk density of the moon's highland crust is substantially lower than generally assumed. This low-bulk crustal density agrees well with data obtained during the final Apollo lunar missions in the early 1970s, indicating that local samples returned by astronauts are indicative of global processes.

"With our new crustal bulk density determination, we find that the average thickness of the moon's crust is between 21 and 27 miles (34 and 43 kilometers), which is about 6 to 12 miles (10 to 20 kilometers) thinner than previously thought," said Mark Wieczorek, GRAIL co-investigator at the Institut de Physique du Globe de Paris. "With this crustal thickness, the bulk composition of the moon is similar to that of Earth. This supports models where the moon is derived from Earth materials that were ejected during a giant impact event early in solar system history."

The map was created by the spacecraft transmitting radio signals to define precisely the distance between them as they orbit the moon in formation. As they fly over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly.

"We used gradients of the gravity field in order to highlight smaller and narrower structures than could be seen in previous datasets," said Jeff Andrews-Hanna, a GRAIL guest scientist with the Colorado School of Mines in Golden. "This data revealed a population of long, linear gravity anomalies, with lengths of hundreds of kilometers, crisscrossing the surface. These linear gravity anomalies indicate the presence of dikes, or long, thin, vertical bodies of solidified magma in the subsurface. The dikes are among the oldest features on the moon, and understanding them will tell us about its early history."

While results from the primary science mission are just beginning to be released, the collection of gravity science by the lunar twins continues. GRAIL's extended mission science phase began Aug. 30 and will conclude Dec. 17. As the end of mission nears, the spacecraft will operate at lower orbital altitudes above the moon.

When launched in September 2011, the probes were named GRAIL A and B. They were renamed Ebb and Flow in January by elementary students in Bozeman, Mont., in a nationwide contest. Ebb and Flow were placed in a near-polar, near-circular orbit at an altitude of approximately 34 miles (55 kilometers) on Dec. 31, 2011, and Jan. 1, 2012, respectively.

NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the mission for NASA's Science Mission Directorate in Washington. GRAIL is part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems of Denver built the spacecraft.

To view the lunar gravity map,

visit http://bit.ly/grailtour .

For more information about the mission,

visit: http://www.nasa.gov/grail .

JPL is a division of the California Institute of Technology in Pasadena.

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

jueves, 6 de diciembre de 2012

NASA - GRAIL's Gravity Map of the Moon

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GRAIL's Gravity Map of the Moon

This image shows the variations in the lunar gravity field as measured by NASA's Gravity Recovery and Interior Laboratory (GRAIL) during the primary mapping mission from March to May 2012. Very precise microwave measurements between two spacecraft, named Ebb and Flow, were used to map gravity with high precision and high spatial resolution. The field shown resolves blocks on the surface of about 12 miles (20 kilometers) and measurements are three to five orders of magnitude improved over previous data. Red corresponds to mass excesses and blue corresponds to mass deficiencies. The map shows more small-scale detail on the far side of the moon compared to the nearside because the far side has many more small craters.

› See video

Image credit: NASA/JPL-Caltech/MIT/GSFC

NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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martes, 29 de mayo de 2012

Astronomy: NASA Lunar Spacecraft Complete Prime Mission Ahead of Schedule

Hi My Friends: A VUELO DE UN QUINDE EL BLOG., NASA mission to study the moon from crust to core has completed its prime mission earlier than expected. The team of NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, with twin probes named Ebb and Flow, is now preparing for extended science operations starting Aug. 30 and continuing through Dec. 3, 2012.

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