Ebb & Flow complete primary mission

Ebb and Flow have completed their prime mission earlier than expected. The mission 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.

The GRAIL mission has gathered unprecedented detail about the internal structure and evolution of the moon. This information will increase our knowledge of how Earth and its rocky neighbors in the inner solar system developed into the diverse worlds we see today.

Since March 8, the spacecraft have operated around the clock for 89 days. From an orbit that passes over the lunar poles, they have collected data covering the entire surface three times. An instrument called the Lunar Gravity Ranging System onboard each spacecraft transmits radio signals that allow scientists to translate the data into a high-resolution map of the moon's gravitational field. The spacecraft returned their last data set of the prime mission May 29. The instruments were turned off at 1 p.m. EDT when the spacecraft were 37 miles (60 kilometers) above the Mare Nectaris.

"Many of the measurement objectives were achieved from analysis of only half the primary mission data, which speaks volumes about the skill and dedication of our science and engineering teams," said Maria Zuber, principal investigator of GRAIL at the Massachusetts Institute of Technology in Cambridge. "While there is a great deal of work yet to be done to achieve the mission's science, it's energizing to realize that what we traveled from Earth to the moon for is right here in our hands."

"GRAIL delivered to Earth over 99.99 percent of the data that could have been collected, which underscores the flawless performance of the spacecraft, instrument and the Deep Space Network," said Zuber.

Both spacecraft instruments will be powered off until Aug. 30. The spacecraft will have to endure a lunar eclipse on June 4. The eclipse and the associated sudden changes in temperature and the energy-sapping darkness that accompanies the phenomena were expected and do not concern engineers about the spacecraft's health.

"Before launch, we planned for all of GRAIL's primary mission science to occur between lunar eclipses," said David Lehman, project manager of GRAIL from NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "But now that we have flown Ebb and Flow for a while, we understand them and are confident they can survive these eclipses in good shape."

The extended mission goal is to take an even closer look at the moon's gravity field. To achieve this, GRAIL mission planners will halve their current operating altitude flying at the lowest altitude that can be safely maintained.

"Orbiting at an average altitude of 14 miles (23 kilometers) during the extended mission, the GRAIL twins will be clearing some of the moon's higher surface features by about 5 miles (8 kilometers)," said Joe Beerer, GRAIL's mission manager. "If Ebb and Flow had feet, I think by reflex they'd want to pull them up every time they fly over a mountain."

Along with mission science, GRAIL's MoonKAM (Moon Knowledge Acquired by Middle school students) education and public outreach program is also extended. To date over 70,000 student images of the moon have been obtained. The MoonKAM program is led by Sally Ride, America's first woman in space, and her team at Sally Ride Science in collaboration with undergraduate students at the University of California in San Diego.

The GRAIL mission is managed by JPL 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. NASA's Deep Space Network is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. Lockheed Martin Space Systems in Denver built the spacecraft.

Flying Formation - Around the Moon at 5,800 KPH

An artist’s depiction of the twin spacecraft (Ebb and Flow) that comprise NASA’s Gravity Recovery And Interior Laboratory (GRAIL) mission. View full image and caption HERE [NASA/Caltech-JPL/MIT].

D. C. Agle
Jet Propulsion Laboratory

Pasadena - The act of two or more aircraft flying together in a disciplined, synchronized manner is one of the cornerstones of military aviation, as well as just about any organized air show. But as amazing as the U.S. Navy's elite Blue Angels or the U.S. Air Force's Thunderbirds are to behold, they remain essentially landlocked, anchored if you will, to our planet and its tenuous atmosphere. What if you could take the level of precision of these great aviators to, say, the moon?

"Our job is to ensure our two GRAIL spacecraft are flying a very, very accurate trail formation in lunar orbit," said David Lehman, GRAIL project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "We need to do this so our scientists can get the data they need."

Essentially, trail formation means one aircraft (or spacecraft in this case), follows directly behind the other. Ebb and Flow, the twins of NASA's GRAIL (Gravity Recovery And Interior Laboratory) mission, are by no means the first to synch up altitude and "air" speed  while zipping over the craters, mountains, hills and rills of Earth's natural satellite. That honor goes to the crew of Apollo 10, who in May 1969 performed a dress rehearsal for the first lunar landing. But as accurate as the astronauts aboard lunar module "Snoopy" and command module "Charlie Brown" were in their piloting, it is hard to imagine they could keep as exacting a position as Ebb and Flow.

"It is an apples and oranges comparison," said Lehman. "Lunar formation in Apollo was about getting a crew to the lunar surface, returning to lunar orbit and docking, so they could get back safely to Earth. For GRAIL, the formation flying is about the science, and that is why we have to make our measurements so precisely."

As the GRAIL twins fly over areas of greater and lesser gravity at 5,800 kilometers per hour, surface features such as mountains and craters, and masses hidden beneath the lunar surface, can influence the distance between the two spacecraft ever so slightly.

How slight a distance change can be measured by the science instrument beaming invisible microwaves back and forth between Ebb and Flow?

NASA/Caltech-JPL/MIT
› Full image and caption

How about one-tenth of one micron? Another way to put it is that the GRAIL twins can detect a change in their position down to one half of a human hair (0.00001 centimeters).  For those of you who are hematologists or vampires (we are not judging here), any change in separation between the two twins greater than one half of a red corpuscle will be duly noted aboard the spacecraft's memory chips for later downlinking to Earth. Working together, Ebb and Flow will make these measurements while flying over the entirety of the lunar surface.

This begs the question, why would scientists care about a change of distance between two spacecraft as infinitesimal as half a red corpuscle a quarter million miles from Earth?

"Mighty oaks from little acorns grow - even in lunar orbit," said Maria Zuber, principal investigator of the GRAIL mission from the Massachusetts Institute of Technology, Cambridge. "From the data collected during these minute distance changes between spacecraft, we will be able to generate an incredibly high-resolution map of the moon's gravitational field.  From that, we will be able to understand what goes on below the lunar surface in unprecedented detail, which will in turn increase our knowledge of how Earth and its rocky neighbors in the inner solar system developed into the diverse worlds we see today."

Getting the GRAIL twins into a hyper-accurate formation from a quarter million miles away gave the team quite a challenge. Launched together on Sept. 10, 2011, Ebb and Flow went their separate ways soon after entering space. Three-and-a-half months and 2.5 million miles (4 million kilometers) later, Ebb entered lunar orbit. Flow followed the next day (New Year's Day 2012).

"Being in lunar orbit is one thing, being in the right lunar orbit for science can be something else entirely," said Joe Beerer, GRAIL's mission manager from JPL. "The twins initial orbit carried them as close to the lunar surface as 56 miles (90 kilometers) and as far out as 5,197 miles (8,363 kilometers), and each revolution took approximately 11.5 hours to complete. They had to go from that to a science orbit of 15 by 53 miles (24.5 by 86 kilometers) and took all of 114 minutes to complete."

To reduce and refine Ebb and Flow's orbits efficiently and precisely required the GRAIL team to plan and execute a series of trajectory modification burns for each spacecraft. And each maneuver had to be just right.

More information about the GRAIL mission is online at: http://www.nasa.gov/grail or http://grail.nasa.gov .

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

"Because each one of these maneuvers was so important, we did a lot of planning and testing for each," said Beerer. "Over eight weeks, we did nine maneuvers with Ebb and 10 with Flow to establish the science formation. We would literally be watching our screens for a signal telling us about an Ebb rocket burn, then go into a meeting about the next burn for Flow. Our schedule was very full."

Today, the calendar for GRAIL's flight team remains a busy one with the day-to-day operations of keeping NASA's lunar twins in synch. But as busy as the team gets, they still have time to peer skyward.

"Next time you look up and see the moon, you might want to take a second and think about our two little spacecraft flying  formation, zooming from pole to pole at 5,800 kph," said Lehman. "They're up there, working together, flying together, getting the data our scientists need. As far as I'm concerned, they're putting on quite a show."

Jupiter-bound Juno captures Earth & Moon

Earth and Moon from NASA's Juno spacecraft, August 26, 2011, from 9.66 million kilometers away. Earth-Moon distance is foreshortened in this line of sight view, that true distance was around 370,000 km, and the Moon's phase was late crescent. Image was taken by the spacecraft's onboard camera JunoCam [NASA/JPL-Caltech].

Pasadena – On its way to the biggest planet in the solar system -- Jupiter, NASA's Juno spacecraft took time to capture its home planet and its natural satellite -- the moon.

"This is a remarkable sight people get to see all too rarely," said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. "This view of our planet shows how Earth looks from the outside, illustrating a special perspective of our role and place in the universe. We see a humbling yet beautiful view of ourselves."

The image was taken by the spacecraft’s camera, JunoCam, on Aug. 26 when the spacecraft was about 6 million miles (9.66 million kilometers) away. The image was taken as part of the mission team’s checkout of the Juno spacecraft. The team is conducting its initial detailed checks on the spacecraft’s instruments and subsystems after its launch on Aug. 5.

Juno covered the distance from Earth to the moon (about 250,000 miles or 402,000 kilometers) in less than one day's time. It will take the spacecraft another five years and 1,740 million miles (2,800 million kilometers) to complete the journey to Jupiter. The spacecraft will orbit the planet's poles 33 times and use its eight science instruments to probe beneath the gas giant's obscuring cloud cover to learn more about its origins, structure, atmosphere and magnetosphere, and look for a potential solid planetary core.

The solar-powered Juno spacecraft lifted off from Cape Canaveral Air Force Station in Florida at 9:25 a.m. PDT (12:25 p.m. EDT) on Aug. 5 to begin its five-year journey to Jupiter.

JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. The Juno mission is part of the New Frontiers Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of the California Institute of Technology in Pasadena.

More information about Juno is online at http://www.nasa.gov/juno and http://missionjuno.swri.edu . You can follow the mission on Twitter at http://www.twitter.com/nasajuno .

HiRISE frames Earth & Moon from Mars

+ Larger view

The High Resolution Imaging Science Experiment (HiRISE) camera would make a great backyard telescope for viewing Mars, and we can also use it at Mars to view other planets.

This is an image of Earth and the moon, acquired on October 3, 2007, by the HiRISE camera on NASA's Mars Reconnaissance Orbiter. At the time the image was taken, Earth was 142 million kilometers (88 million miles) from Mars, giving the HiRISE image a scale of 142 kilometers (88 miles) per pixel, an Earth diameter of about 90 pixels and a moon diameter of 24 pixels.

The phase angle is 98 degrees, which means that less than half of the disk of the Earth and the disk of the moon have direct illumination. We could image Earth and moon at full disk illumination only when they are on the opposite side of the sun from Mars, but then the range would be much greater and the image would show less detail.

On the day this image was taken, the Japanese Kayuga (Selene) spacecraft was en route from the Earth to the moon, and has since returned spectacular images and movies (see http://www.jaxa.jp/projects/sat/selene/index_e.html).

On the Earth image we can make out the west coast outline of South America at lower right, although the clouds are the dominant features. These clouds are so bright, compared with the moon, that they are saturated in the HiRISE images. In fact the red-filter image was almost completely saturated, the Blue-Green image had significant saturation, and the brightest clouds were saturated in the infrared image. This color image required a fair amount of processing to make a nice-looking release. The moon image is unsaturated but brightened relative to Earth for this composite.

The lunar images are useful for calibration of the camera.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo. Image Credit: NASA/JPL-Caltech/University of Arizona