GRAIL Mission solves 50-year old Mystery of Lunar Surface Gravity: GRAIL Science Reports
Lunar Reconnaissance Orbiter photographs GRAIL Crash Site |
March 19, 2013 |
The Lunar Reconnaissance Orbiter Camera has successfully acquired images of the crash sites of the two GRAIL Spacecraft that were purposefully crashed into the Lunar Surface on December 17, 2012 after completing their science mission mapping the Moon's gravity in unprecedented detail.
The LRO Camera passed over the crash site, the southern slope of a mountain that lies south of the crater Mouchez and northeast of the crater Philolaus in February and imaged the area to allow teams to look for the two impact craters.
The two GRAIL spacecraft left craters with a diameter of about five meters with dark ejecta located around the craters with less ejecta in the south because the GRAIL twins were approaching their crash site from south to north. The dark ejecta are currently puzzling scientists because ejecta from fresh craters on the Moon typically have a higher reflectance than the target material because the subsurface regolith of the Moon is lighter toned that than found directly at the surface. This is due to the effects of cosmic radiation, solar wind, and micrometeorite impacts that cause the uppermost layer of regolith to darken.
The current theory is that carbon from the spacecraft and its leftover fuel caused the regolith to darken. Due to the energy of impact, the carbon from the spacecraft may have been released and mixed with and coated the ejecta.
With LRO providing imagery of the crash site, it is now possible to precisely locate the final resting place of the two spacecraft on the 2,500 meter high mountain:
The two impact craters are about 2,210 meters apart.
The LRO Camera passed over the crash site, the southern slope of a mountain that lies south of the crater Mouchez and northeast of the crater Philolaus in February and imaged the area to allow teams to look for the two impact craters.
The two GRAIL spacecraft left craters with a diameter of about five meters with dark ejecta located around the craters with less ejecta in the south because the GRAIL twins were approaching their crash site from south to north. The dark ejecta are currently puzzling scientists because ejecta from fresh craters on the Moon typically have a higher reflectance than the target material because the subsurface regolith of the Moon is lighter toned that than found directly at the surface. This is due to the effects of cosmic radiation, solar wind, and micrometeorite impacts that cause the uppermost layer of regolith to darken.
The current theory is that carbon from the spacecraft and its leftover fuel caused the regolith to darken. Due to the energy of impact, the carbon from the spacecraft may have been released and mixed with and coated the ejecta.
With LRO providing imagery of the crash site, it is now possible to precisely locate the final resting place of the two spacecraft on the 2,500 meter high mountain:
- GRAIL-A: 75.609°N, 333.407°E, 750 meters above surrounding plains
- GRAIL-B: 75.651°N, 333.168°E, 1,040 meters above surrounding plains
The two impact craters are about 2,210 meters apart.
GRAIL Twins crash into the Moon to complete highly successful Mission
December 17, 2012
NASA’s Gravity Recovery and Interior Laboratory (GRAIL) Spacecraft have ended their mission on Monday by making a targeted crash landing on the lunar surface. The mission of the two washing-machine-sized spacecraft, named Ebb and Flow, had a duration of 464 days. The twin vehicles spent the majority of that in lunar orbit.
NASA’s GRAIL twins launched atop a United Launch Alliance Delta II Rocket from the Cape Canaveral Air Force Station on September 10, 2011. After their exciting ride to orbit, the two spacecraft parted ways, making a slow, but fuel-efficient, low-energy transfer to the Moon via the Sun-Earth Lagrange Point L1. This trajectory was chosen to allow the two spacecraft to separate in order to allow teams to focus on one spacecraft at a time during Lunar Orbit Insertion. Also, during the long cruise, the two spacecraft underwent checkouts of their amazingly precise science payloads. GRAIL-A (Ebb) arrived in lunar orbit on New Year’s Eve, firing its main engine for 40 minutes to slow itself down by nearly 700 Kilometers per Hour in order to enter an elliptical orbit. |
The other twin, GRAIL-B (Flow) made its Lunar Orbit Insertion Burn on January 1, 2012 to set the stage for a year filled with a variety of operations in lunar orbit, also kicking off a precisely choreographed sequence of maneuvers that the two vehicles executed in order to enter their science formation. It took about two months to get the two spacecraft organized – placing the twins in an identical orbit, flying in close formation with Flow leading the way and Ebb hanging back by about 150 Kilometers. Once both spacecraft were in position, the busy science phase of the mission began. The first of three Mapping Cycles of the Moon began on March 7, 2012.
GRAIL used two spacecraft flying in close formation in lunar orbit to measure the Moon’s gravity at an unprecedented accuracy. Measurements were made by using doppler shifting which utilizes changes in an orbiter’s radio frequency that changes as the spacecraft’s orbital velocity varies ever so slightly due to the gravitational field of the body it orbits. If a spacecraft flies over an area of concentrated gravity, it is pulled down and speeds up, and when it flies over an area where the gravitational field is weaker, it slows down. This can be measured via doppler tracking using the spacecraft to emit radio waves that are picked up by ground stations on Earth.
GRAIL used two spacecraft flying in close formation in lunar orbit to measure the Moon’s gravity at an unprecedented accuracy. Measurements were made by using doppler shifting which utilizes changes in an orbiter’s radio frequency that changes as the spacecraft’s orbital velocity varies ever so slightly due to the gravitational field of the body it orbits. If a spacecraft flies over an area of concentrated gravity, it is pulled down and speeds up, and when it flies over an area where the gravitational field is weaker, it slows down. This can be measured via doppler tracking using the spacecraft to emit radio waves that are picked up by ground stations on Earth.
Because the Moon only shows one side of it to Earth, two spacecraft are needed to generate a full gravity map, because a single spacecraft could not be tracked from Earth while in eclipse, hidden by the Moon. The two GRAIL spacecraft tracked the other’s relative velocity with an accuracy of 50 nanometers per second to examine even slight variations in the gravitational field of the Moon, both, on a global and local scale.
Along with GRAIL’s Science Mission, another project involving the two GRAIL twins began. MoonKAM, operated by Sally Ride Science, flew four cameras on each of the two vehicles to acquire images requested by students around the world. Nearly 120,000 images acquired by MoonKAM have been published to date. MoonKAM was used to engage middle school students into learning about the Moon by analyzing images they requested to be taken by GRAIL MoonKAM. On May 29, 2012, after three Mapping Cycles, GRAIL’s primary science mission ended. At that time, teams were already busy analyzing data that was provided by the two spacecraft. Earlier in the mission, it was announced that the GRAIL mission would be extended by three additional mapping cycles. On June 4, the GRAIL twins had to endure a lunar eclipse during which their solar arrays received no sunlight to charge the vehicle’s batteries. Both spacecraft made it through the eclipse alive and in good condition. Originally, the GRAIL mission was planned to occur in between lunar eclipses because the spacecraft were not expected to survive two hours in darkness. After flying the two spacecraft for a while, teams saw that the twins were performing better than expected and could survive an eclipse. After the primary science mission and the eclipse, the spacecraft spent some quiet time in lunar orbit as their orbital altitude decreased. With the two vehicles closer to the surface, the orbiters were able to examine local gravitational properties as opposed to the more global and regional view that the primary mission provided. The extended science phase started on August 30, 2012 as the two spacecraft orbited at an average altitude of 23 Kilometers which is within eight Kilometers of the Moon's higher surface features. The extended science mission continued until December 15 to maximize data return. Last Friday, the two GRAIL twins performed a final orbital adjustment, breaking their science formation after months of flying around the Moon in tandem. The final days of the GRAIL mission were dedicated to engineering checkouts. |
GRAIL - Lunar Gravity / Gravity Gradient Maps
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On Monday, the GRAIL orbiters started their final orbits around the Moon, getting closer and closer to its surface, before taking one last dive to crash into the lunar surface.
On their final orbit, the twins passed from south to north until a 2,400-meter mountain near a crater named Goldschmidt got into their way and they made their crash landing, as planned by the GRAIL mission team that targeted both GRAIL spacecraft to impact this particular surface feature for a number of reasons.
On their final orbit, the twins passed from south to north until a 2,400-meter mountain near a crater named Goldschmidt got into their way and they made their crash landing, as planned by the GRAIL mission team that targeted both GRAIL spacecraft to impact this particular surface feature for a number of reasons.
The mission of the GRAIL twins was focused on science, and so was their demise. The impact of the two spacecraft will help scientists to examine the mechanical properties of the mountain and the lunar crust in general. For that, the Lunar Reconnaissance Orbiter was in position to observe the impact with its instruments. Although the area was in the dark at the time of the crash, there was a small possibility of volatiles being ejected during impact which LRO could analyze. Also, LRO took high-resolution images of the impact site before the crash and the spacecraft will image the site again in the coming months to enable teams to perform visual analysis of the impact site.
In addition, choosing a crash site this far north avoided the possibility of the GRAIL twins impacting at or near one of the historical landing sites on the surface of the Moon where the Apollo, Surveyor, Luna and Lunokhod spacecraft landed. On their last orbit around the Moon, the GRAIL twins performed a burn-to-depletion maneuver, burning their main engines until their fuel tanks were empty. GRAIL-A had ~20m/s worth of fuel left and GRAIL-B had nearly 26m/s. The depletion burn of Ebb was 4 minutes and 3 seconds in duration and the engine on Flow burned for 5 minutes and 7 seconds. Knowing exactly how much fuel was remaining will help engineers plan future mission and improve simulations for future flights. After their final burn, the GRAIL spacecraft were on their final trajectory, without fuel and on their planned collision course with the Moon’s surface. The first of the GRAIL Twins to crash into the Moon was Ebb. The vehicle made its impact at a velocity of 1.7 Kilometers per second at 22:28:51 UTC. Flow followed 30 seconds later impacting about 3 Kilometers from Ebb. The impact site is located at 75.62 degrees north and 26.83 degrees west. After a mission of 464 days, 9 hours and 20 minutes, the two GRAIL Spacecraft were no more. "We will miss our lunar twins, but the scientists tell me it will take years to analyze all the great data they got, and that is why we came to the moon in the first place," said GRAIL project manager David Lehman of NASA's Jet Propulsion Laboratory. "So long, Ebb and Flow, and we thank you." |
Although the GRAIL spacecraft have ceased to exist, their mission will provide a lot more knowledge about the Moon’s gravitational field, its interior composition and its history as more data is analyzed. Teams have just presented the initial findings of the primary science mission, but scientists are still busy piling through data provided during the extended mission.
The crash-site of the GRAIL twins will be named in honor of Sally Ride, NASA announced. Ride was America’s first women in space and collaborator for the GRAIL mission. She funded Sally Ride Science which administered the GRAIL MoonKAM mission.
"Sally was all about getting the job done, whether it be in exploring space, inspiring the next generation, or helping make the GRAIL mission the resounding success it is today," said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "As we complete our lunar mission, we are proud we can honor Sally Ride's contributions by naming this corner of the moon after her."
The crash-site of the GRAIL twins will be named in honor of Sally Ride, NASA announced. Ride was America’s first women in space and collaborator for the GRAIL mission. She funded Sally Ride Science which administered the GRAIL MoonKAM mission.
"Sally was all about getting the job done, whether it be in exploring space, inspiring the next generation, or helping make the GRAIL mission the resounding success it is today," said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "As we complete our lunar mission, we are proud we can honor Sally Ride's contributions by naming this corner of the moon after her."
GRAIL Twins complete final Orbit Adjustment Maneuver
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December 15, 2012
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The two GRAIL Spacecraft, Ebb and Flow, completed their final orbit adjustment on Friday to seal their fate and place the two vehicles on a trajectory for lunar impact on Monday.
The maneuver was performed at 15:07 UTC on Friday. Ebb ignited its main engines for 55.8 seconds to change its velocity by 4.6 meters per second. Sixteen seconds after ignition on Ebb, the Flow Spacecraft started its burn which was 55.4 seconds in duration for a delta-V of 4.6 m/s.
"NASA wanted to rule out any possibility of our twins hitting the surface anywhere near any of the historic lunar exploration sites like the Apollo landing sites or where the Russian Luna probes touched down," said David Lehman, GRAIL project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Our navigators calculated the odds before this maneuver as about seven in a million. Now, after these two successful rocket firings, there is zero chance."
With this burn complete, the GRAIL mission is approaching its ultimate end which is set for Monday at 22:28 UTC when the two spacecraft will crash into the lunar surface.
For more about GRAIL’s lunar impact, visit the December 13 Mission Update right below this.
The maneuver was performed at 15:07 UTC on Friday. Ebb ignited its main engines for 55.8 seconds to change its velocity by 4.6 meters per second. Sixteen seconds after ignition on Ebb, the Flow Spacecraft started its burn which was 55.4 seconds in duration for a delta-V of 4.6 m/s.
"NASA wanted to rule out any possibility of our twins hitting the surface anywhere near any of the historic lunar exploration sites like the Apollo landing sites or where the Russian Luna probes touched down," said David Lehman, GRAIL project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Our navigators calculated the odds before this maneuver as about seven in a million. Now, after these two successful rocket firings, there is zero chance."
With this burn complete, the GRAIL mission is approaching its ultimate end which is set for Monday at 22:28 UTC when the two spacecraft will crash into the lunar surface.
For more about GRAIL’s lunar impact, visit the December 13 Mission Update right below this.
NASA's GRAIL Twins prepare for Lunar Impact on Monday
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December 13, 2012
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The GRAIL Twins, Ebb and Flow, have started the final few days in orbit around the Moon, getting set to perform a guided crash landing on the Lunar Surface on Monday, December 17, to put a definitive end to their splendid mission.
Currently, the two spacecraft are still operating in science mode, making the final observations of the Moon’s gravity. On Friday, the vehicles will make a small orbit adjustment and leave their close science formation they had been in since re-starting science activities in August. For the rest of their operational lives, the two GRAIL spacecraft will complete a number of engineering tests that will verify a number of spacecraft functions changing back and forth between operational modes that would have been used in case of any vehicle problems during the mission. Once all tests involving the payloads are complete, GRAIL’s science equipment will be deactivated. On Monday, the two spacecraft will make their final orbits around the Moon, coming closer to the surface than ever before. The twins will pass from South to North on their final orbit for an impact in the Northern latitudes of the Moon. During this final pass, the two vehicle will make one last engineering test. "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." Teams are certain that the propellant tanks are almost empty, precluding GRAIL from continuing its mission, but the exact fuel level inside the vehicle’s tanks is unknown. To precisely determine the amount of fuel left in the tanks of the twins, they will perform a depletion burn that could take up to nine minutes. The exact duration of the burn will enable engineers to determine the amount of propellant that was left to help improve engineering models and propulsion procedures for future missions. The mountain the two spacecraft are targeting is part of the rim of an impact crater is located at 75.62 degrees North latitude and 26.63 West longitude. The mountain has an elevation of about 2 Kilometers and has not been named yet. |
The two spacecraft will approach from the South, flying very close above the surface of the Moon until the elevated terrain gets in their way and they crash. Leading the way will be Ebb making its impact at 22:28:40 UTC on Monday followed 20 seconds later by the Flow spacecraft. The twins will impact about 20 to 40 Kilometers apart, crashing at a velocity of 1.7 Kilometers per second coming in at a very shallow angle.
"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."
The impact area will be in the dark at the time, so that no images of the impact are expected. The Lunar Reconnaissance Orbiter will be passing over the area at the time after making a slight orbit adjustment recently. LRO will try to detect any volatiles that might be released during the impacts, but the chances of that are very slim. The LRO Spacecraft has recently acquired images of the crash site and will repeat the imaging after the impact to provide a comparison and enable scientists to study the impact craters the two vehicles will leave. This will provide information on the mechanical properties of the mountain and it will also provide data on how the lunar surface behaves during impacts. The marks the two spacecraft will leave are expected to be fairly small as the two vehicles are fairly light when their fuel tanks are depleted.
The crash site was chosen based on two factors. The GRAIL mission was all about science and teams wanted to extend the science phase as long as possible to allow GRAIL to provide a very precise gravity map of the Orientale Basin, a relatively fresh impact basin.
The impact area will be in the dark at the time, so that no images of the impact are expected. The Lunar Reconnaissance Orbiter will be passing over the area at the time after making a slight orbit adjustment recently. LRO will try to detect any volatiles that might be released during the impacts, but the chances of that are very slim. The LRO Spacecraft has recently acquired images of the crash site and will repeat the imaging after the impact to provide a comparison and enable scientists to study the impact craters the two vehicles will leave. This will provide information on the mechanical properties of the mountain and it will also provide data on how the lunar surface behaves during impacts. The marks the two spacecraft will leave are expected to be fairly small as the two vehicles are fairly light when their fuel tanks are depleted.
The crash site was chosen based on two factors. The GRAIL mission was all about science and teams wanted to extend the science phase as long as possible to allow GRAIL to provide a very precise gravity map of the Orientale Basin, a relatively fresh impact basin.
With GRAIL flying just two Kilometers above the rim of the basin, teams detected the highest gravity measurements of the entire mission. GRAIL’s map of the basin will be more refined that any other gravity map generated of the Moon.
The second factor were the historic landing sites that are located on the near side of the Moon. To avoid crashing into one of the Apollo, Surveyor, Luna or Lunokhod sites, teams decided to crash the GRAIL twins in the far North regions. Now, with science operations complete, fuel tanks empty and the orientation of Sun, GRAIL & Moon no longer allowing science measurements, it is time to say Goodbye to the two little spacecraft. "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." |
First GRAIL Science Data reveals new Feature of Lunar Geology - Science Report
NASA's GRAIL Spacecraft approach the End of their Mission
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December 5, 2012
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NASA’s GRAIL Mission has been progressing quietly as the two Lunar Orbiters have been gathering valuable science data over the course of the extended mission that began back in August. Now, the mission is approaching its end with final science observations being made before the two Spacecraft, Ebb and Flow, end their mission by making a crash landing on the Lunar surface.
Recently, NASA and the GRAIL Science Team have kept quiet in terms of press releases and mission updates as teams are busy piling through the data provided by the two orbiters over the past few months. The first science results of the GRAIL mission are being presented at the American Geophysical Union’s Fall Meeting on December 5. Recently, bad news had been coming from the MoonKAM Mission that is managed by Sally Ride Science and features four cameras on each of the Spacecraft that are being used to acquire images of the lunar surface for educational purposes. Three of the four cameras have 6-millimeter lenses while the remaining camera has a 50-millimeter lens. The 6mm cameras point +/-60 degrees forward and back while the single 50mm camera points down. Last week, the MoonKAM team reported that the cameras on both spacecraft were hit by high-energy particles and solar radiation resulting from solar flares. As a result, MoonKAM services were interrupted. |
“Over the Thanksgiving holiday the cameras stopped functioning properly. We are no longer able to command them to take pictures or download image files,” the MoonKAM team said in an E-Mail to MoonKAM participants. The MoonKAM cameras are vulnerable to radiation hits as they do not feature radiation-hardened electronics. The scientific payload of the GRAIL twins was not affected by the event.
After arriving in Lunar Orbit on New Years Eve and January 1, 2012, the two GRAIL Spacecraft completed a complex ballet of maneuvers to enter their close-formation to begin the primary science phase on March 7, 2012. GRAIL completed three mapping cycles of the Moon, flying at different altitudes and distances of the spacecraft to each other in order to look at the gravitational field of the Moon on a regional and global scale. With data acquired during these first mapping cycles, teams were able to generate the most accurate map of the Moon’s gravitational field, even exceeding their scientific requirements. GRAIL set out to improve our knowledge on gravity on the far side of the Moon by a factor of 1,000 and that of the near side by a factor of 100. To further increase science data return, the GRAIL mission was extended.
After arriving in Lunar Orbit on New Years Eve and January 1, 2012, the two GRAIL Spacecraft completed a complex ballet of maneuvers to enter their close-formation to begin the primary science phase on March 7, 2012. GRAIL completed three mapping cycles of the Moon, flying at different altitudes and distances of the spacecraft to each other in order to look at the gravitational field of the Moon on a regional and global scale. With data acquired during these first mapping cycles, teams were able to generate the most accurate map of the Moon’s gravitational field, even exceeding their scientific requirements. GRAIL set out to improve our knowledge on gravity on the far side of the Moon by a factor of 1,000 and that of the near side by a factor of 100. To further increase science data return, the GRAIL mission was extended.
After completing the primary science mission, GRAIL went into stand-by and let its orbit evolve over time, coming closer and closer to the lunar surface. On August 30, 2012, the extended science phase began, featuring an additional three mapping cycles plus targeted observations. During the extended mission, the orbiters were at an average altitude of 23 Kilometers, which is within eight Kilometers of the Moon's higher surface features, in order to track even minute changes in the distance between the two Spacecraft and record this profile. The distance between the spacecraft changes slightly as they fly over areas of greater and lesser gravity caused by visible features such as mountains, craters and masses hidden beneath the lunar surface. At lower altitudes, the instruments acquire data showing localized effects of the Moon’s Gravitational Field reflecting smaller features above or beneath the lunar surface.
With GRAIL heading towards the end of the extended mission, the orbiters are now in an extremely low orbit and their fuel tanks are nearly empty. In mid-December, the GRAIL science mission will be ended. One of the final scientific observations will be low-flyovers of Mare Orientale to obtain more detailed gravity information from that area. Whether the two vehicles will make a targeted impact has not been announced yet. Should teams decide to leave the spacecraft in orbit and let orbital mechanics take control of the spacecraft, Ebb and Flow should impact the lunar surface within a few weeks. |
Mare Orientale
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GRAIL Mission enters Extended Science Phase |
September 2, 2012 |
NASA's twin Gravity Recovery and Interior Laboratory Spacecraft have started their extended mission on time and as planned on August 30, 2012 spending three more months mapping the gravitational field of the Moon from their lowering orbital position in lunar orbit.
The official start of Mapping Cycle 1 of the extended Science Mission came at 16:28 UTC on August 30 while the two spacecraft were flying over the Moon's Ocean of Storms at an altitude of 30 Kilometers. At that time, the Lunar Gravity Ranging System on both vehicles was energized and the spacecraft began acquiring precise range data again. After completing the primary mission of three complete Mapping Cycles, it was announced that GRAIL would get an additional three cycles to produce an even better model of the Moon's interior. "The data collected during GRAIL's primary mission team are currently being analyzed and hold the promise of producing a gravity field map of extraordinary quality and resolution," said Maria Zuber, principal investigator for GRAIL from the Massachusetts Institute of Technology in Cambridge. |
"Mapping at a substantially lower altitude during the extended mission, and getting an even more intimate glimpse of our nearest celestial neighbor, provides the unique opportunity to globally map the shallow crust of a planetary body beyond Earth."
During the extended mission, GRAIL's Orbit will get lower and lower with an average altitude of 23 Kilometers, which is within eight Kilometers of the Moon's higher surface features. GRAIL tracks even minute changes in the distance between the two Spacecraft and record this profile. The distance between the spacecraft changes slightly as they fly over areas of greater and lesser gravity caused by visible features such as mountains, craters and masses hidden beneath the lunar surface. At lower altitudes, the instruments acquire data showing localized effects of the Moon’s Gravitational Field reflecting smaller features above or beneath the lunar surface while the prime mission generated a more global look at the Moon's gravitational properties. During the extended mission GRAIL will pick up even small sub-surface features such as simple craters, mountains and rilles. In addition, the vehicles can examine the phenomenon of Mascons again. These are Mass Concentrations beneath the surface that are not well known and are a focus of one of GRAIL's Science Objectives.
"The twins have endured the lunar eclipse of June 4, 2012, and 26 rocket burns since arriving in lunar orbit at the beginning of the year. Down here in our control room, with all the planning and mission operations we have been doing, it feels as though we've been riding right along with them. Of course, they have the better view," said David Lehman, GRAIL project manager from NASA's Jet Propulsion Laboratory. During the science mission, both GRAIL Vehicles have to actively maintain their orbits to remain at the proper range for science measurements without drifting to far from each other or coming too close. In addition, altitude burns are performed to extend the orbit's lifetime through December. "Ebb and Flow, and our mission operations team, are both doing great, which is certainly notable considering all the milestones and challenges they have experienced," Lehmann noted.
On December 3, 2012, the mission will come to an end. A short period of decommissioning will be performed before the two spacecraft impact the lunar surface.
During the extended mission, GRAIL's Orbit will get lower and lower with an average altitude of 23 Kilometers, which is within eight Kilometers of the Moon's higher surface features. GRAIL tracks even minute changes in the distance between the two Spacecraft and record this profile. The distance between the spacecraft changes slightly as they fly over areas of greater and lesser gravity caused by visible features such as mountains, craters and masses hidden beneath the lunar surface. At lower altitudes, the instruments acquire data showing localized effects of the Moon’s Gravitational Field reflecting smaller features above or beneath the lunar surface while the prime mission generated a more global look at the Moon's gravitational properties. During the extended mission GRAIL will pick up even small sub-surface features such as simple craters, mountains and rilles. In addition, the vehicles can examine the phenomenon of Mascons again. These are Mass Concentrations beneath the surface that are not well known and are a focus of one of GRAIL's Science Objectives.
"The twins have endured the lunar eclipse of June 4, 2012, and 26 rocket burns since arriving in lunar orbit at the beginning of the year. Down here in our control room, with all the planning and mission operations we have been doing, it feels as though we've been riding right along with them. Of course, they have the better view," said David Lehman, GRAIL project manager from NASA's Jet Propulsion Laboratory. During the science mission, both GRAIL Vehicles have to actively maintain their orbits to remain at the proper range for science measurements without drifting to far from each other or coming too close. In addition, altitude burns are performed to extend the orbit's lifetime through December. "Ebb and Flow, and our mission operations team, are both doing great, which is certainly notable considering all the milestones and challenges they have experienced," Lehmann noted.
On December 3, 2012, the mission will come to an end. A short period of decommissioning will be performed before the two spacecraft impact the lunar surface.
GRAIL completes primary Mission - Prepares for Lunar Eclipse
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May 30, 2012
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NASA's twin Gravity Recovery And Interior Laboratory (GRAIL) Spacecraft, Ebb and Flow, have completed the primary GRAIL Mission on May 29, 2012 when the final data set was downlinked to Earth. GRAIL's Science Team is already in the process of validating and examining the data that was obtained while both spacecraft were orbiting the Moon in perfect formation for nearly 90 days. "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. GRAIL has collected data about the internal structure and evolution of the moon that will increase our knowledge of how Earth and its rocky neighbors in the inner solar system developed. To acquire its high resolution map of the Moon's gravitational field, GRAIL covered the lunar surface three times as part of three Mapping Cycles having the spacecraft fly at different altitudes and different distances to each other. GRAIL tracks even minute changes in the distance between the two Spacecraft and record this profile. The distance between the spacecraft changes slightly as they fly over areas of greater and lesser gravity caused by visible features such as mountains, craters and masses hidden beneath the lunar surface called Mascons (Mass Concentrations).
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The greater the orbital altitude of the vehicles is, the more global the gravitational map gets. Low altitudes cause localized phenomena like Mascons to be picked up by the Lunar Gravity Ranging System onboard each spacecraft. For a detailed GRAIL Science Overview, refer to our Mission Section.
The Mission is now preparing for the Lunar Eclipse of June 4. Originally, the Mission was designed to be completed between two lunar Eclipses in 2012 as the GRAIL vehicles were not designed to survive an eclipse. "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 in Pasadena, California. "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." At 11:03 GMT on June 4, the lunar eclipse will begin. It has a duration of 128 minutes during which Ebb and Flow will not receive any Sunlight for power generation via their solar arrays. Also, the vehicles will pass through a sudden change of temperature as light fades away for two hours. To prepare for the eclipse, GRAIL's instruments have been powered down on May 29 to make sure the spacecraft only consume power for essential systems. Both vehicles have to survive the eclipse to continue the mission. One GRAIL Spacecraft can not fulfill any of the objectives of the extended mission. GRAIL's Systems will be activated again on August 30 to begin the extended mission shortly thereafter. Over the extended Mission, GRAIL’s Orbits will be lowered. GRAIL’s Mean Altitude will decrease to about 22.5 Kilometers with Ebb and Flow skimming over the lunar surface as low as 7 Kilometers at their closest approaches (Periapsis). At lower altitudes, the instruments acquire data showing localized effects of the Moon’s Gravitational Field reflecting smaller features above or beneath the lunar surface.
The Mission is now preparing for the Lunar Eclipse of June 4. Originally, the Mission was designed to be completed between two lunar Eclipses in 2012 as the GRAIL vehicles were not designed to survive an eclipse. "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 in Pasadena, California. "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." At 11:03 GMT on June 4, the lunar eclipse will begin. It has a duration of 128 minutes during which Ebb and Flow will not receive any Sunlight for power generation via their solar arrays. Also, the vehicles will pass through a sudden change of temperature as light fades away for two hours. To prepare for the eclipse, GRAIL's instruments have been powered down on May 29 to make sure the spacecraft only consume power for essential systems. Both vehicles have to survive the eclipse to continue the mission. One GRAIL Spacecraft can not fulfill any of the objectives of the extended mission. GRAIL's Systems will be activated again on August 30 to begin the extended mission shortly thereafter. Over the extended Mission, GRAIL’s Orbits will be lowered. GRAIL’s Mean Altitude will decrease to about 22.5 Kilometers with Ebb and Flow skimming over the lunar surface as low as 7 Kilometers at their closest approaches (Periapsis). At lower altitudes, the instruments acquire data showing localized effects of the Moon’s Gravitational Field reflecting smaller features above or beneath the lunar surface.
A total of three additional Mapping Cycles are planned. On December 3, 2012, the mission will come to an end. A short period of decommissioning will be performed before the two spacecraft impact the lunar surface. To further increase science data return, Teams are currently evaluating a targeted Mission Termination meaning that the GRAIL Orbiters will make a targeted Crash on a picked site on the Lunar Surface that is in sight of instruments on NASA’s Lunar Reconnaissance Orbiter. A decision on that will be made as the mission progresses and propellant is consumed to support the science phase of the mission.
With GRAIL's mission extended through December, the MoonKAM Project will also continue. So far, over 70,000 student images of the moon have been obtained. "MoonKAM is based on the premise that if your average picture is worth a thousand words, then a picture from lunar orbit may be worth a classroom full of engineering and science degrees," said Maria Zuber. MoonKAM is managed by Sally Ride Science. |
Did you know?
If you are interested in learning more about space in general, there are plenty of space science lessons on the internet to help people of all ages!
If you are interested in learning more about space in general, there are plenty of space science lessons on the internet to help people of all ages!
GRAIL Mission extended, First MoonKAM Images released
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March 24, 2012
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After starting its Science Phase on March 7, the GRAIL Mission is proceeding as planned with both Spacecraft in identical Orbits around the Moon and in excellent condition.
Last week, it became clear that the Mission Extension for the GRAIL Mission has been approved allowing the Spacecraft to continue data acquisition until December 2012. Originally, the Science Phase of the Mission was planned to last 3 Mapping Cycles or 82 Days for Spacecraft Decommissioning in late May and Mission Termination by July 13. The Mission Extension will enable scientists to obtain more data in order to get a more detailed picture of the Moon’s Gravity and Interior. A revised Mission Timeline can be found here. Over the extended Mission, GRAIL’s Orbits will be lowered. GRAIL’s Mean Altitude will decrease to about 22.5 Kilometers with Ebb and Flow skimming over the lunar surface as low as 7 Kilometers at their closest approaches (Periapsis). At lower altitudes, the instruments acquire data showing localized effects of the Moon’s Gravitational Field reflecting smaller features above or beneath the lunar surface. In order to be able to continue the Science Mission, both GRAIL Orbiters have to survive a Lunar Eclipse on June 4, 2012. Originally, the two Spacecraft were not expected operate through the eclipse during which no sunlight will illuminate their solar arrays forcing them to run on battery power only. However, evaluations during the mission revealed that the spacecraft should be able to survive the eclipse if configured properly. Initial analysis were performed with particularly conservative calculation methods and Mission Managers are confident that there should be no problem associated with the eclipse that will be 128 minutes in duration starting at 11:03 GMT on June 4. During Mapping Cycle 4, the Spacecraft will be configured to fully charge their batteries and power down equipment that is not needed for crucial systems support. When the eclipse is over, systems will be powered up once again and science operations will resume for Mapping Cycle 5. Assuming no problems in the extended mission, GRAIL will perform a total of 10 Mapping Cycles (Cycle 4 will only return limited data) instead of 3. To further increase science data return, Teams are currently evaluating a targeted Mission Termination meaning that the GRAIL Orbiters will make a targeted Crash on a picked site on the Lunar Surface that is in sight of instruments on NASA’s Lunar Reconnaissance Orbiter. In the original Mission Plan, the Spacecraft would not have made a targeted impact. A decision on that will be made as the mission progresses and propellant is consumed to support the prime science mission. Meanwhile, the MoonKAM Team has released the first Images that were acquired as part of the MoonKAM Education and Public Outreach Effort. Students from the Emily Dickinson Elementary School in Bozeman, Montana, received the first images the Cameras mounted on both GRAIL Vehicles took. The school received this honor of being the first to pick pictures by winning the GRAIL naming contest giving the two Orbiter the names Ebb and Flow back in January. These first images were acquired between March 15 and 17 and were downlinked on March 20. The MoonKAM Team relayed the images to the school. "MoonKAM is based on the premise that if your average picture is worth a thousand words, then a picture from lunar orbit may be worth a classroom full of engineering and science degrees," said Maria Zuber, GRAIL mission principal investigator from the Massachusetts Institute of Technology in Cambridge, Mass. "Through MoonKAM, we have an opportunity to reach out to the next generation of scientists and engineers. It is great to see things off to such a positive start." MoonKAM is managed by Sally Ride Science. The GRAIL Mission is currently in Mapping Cycle 1 which will conclude on April 3 and transition to MC2. At the End of Mapping Cycle 1, the Ebb Spacecraft that is trailing behind GRAIL-B or Flow, will make a small adjustment of its orbit to close in on GRAIL-B to decrease the distance between the two Orbiters. The current distance between Ebb and Flow is 188 Kilometers as the vehicles orbit the Moon in a 40 by 68-Kilometer Orbit. Photo Gallery: GRAIL MoonKAM Images |
GRAIL Science Phase Underway
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March 7, 2012
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_The Twin GRAIL Spacecraft have officially started the Science Data Acquisition Phase of the Mission on March 7 at 1:15 GMT (March 6, 8:15pm EST) – 178 Days and 12 Hours into the Flight. With that, the Mission is somewhat ahead of the Mission Timeline that shows the Science Phase starting on March 8.
A complex system of communications between the two spacecraft themselves and Stations on Earth will now be busy for at least 84 Days as the Science Phase progresses. GRAIL will track even minute changes in the distance between the two Spacecraft and record this profile. The distance between the spacecraft will change slightly as they fly over areas of greater and lesser gravity caused by visible features such as mountains, craters and masses hidden beneath the lunar surface called Mascons (Mass Concentrations). For a detailed overview of GRAIL’s Science Objectives and Mapping Techniques, please visit our GRAIL Section. With the science phase now underway, mission personnel will be busy tracking the progress the Orbiters make. "The initiation of science data collection is a time when the team lets out a collective sigh of relief because we are finally doing what we came to do," |
_said Maria Zuber, principal investigator for
the GRAIL mission at the Massachusetts Institute of Technology in
Cambridge, "but it is also a time where we have to put the coffee pot
on, roll up our sleeves and get to work." Mission Controllers will be
communicating with the Spacecraft via two 8-hour Deep Space Network
Communication Passes each day. During these Communication Windows,
Science Data and MoonKAM Images will be downlinked while commands will
the uplinked to the vehicles. MoonKAM will start gathering photos of the
Lunar Surface soon after a short commissioning phase to check all cameras which is underway
now. The official date for the beginning of the MoonKAM Mission is March
12. First images of the Moon are expected shortly thereafter. Mission
Personnel is now in the process of evaluating initial data and verifying
that the two spacecraft and all systems are working as expected and
providing the best possible data resolution.
The two spacecraft are currently in a polar, near circular orbit around the Moon with a mean altitude of 54.5 Kilometers. GRAIL-B, also called Flow, is leading the convoy as planned because the instrument construction requires GRAIL-A – or Ebb – to trail behind the other twin so that Science Data can be gathered. Over the course of the Science Phase, the orbit and distance between the Spacecraft will change as scientists want a full picture of the gravitational field of the Moon. Close range lets the spacecraft detect local gravity elements while a bigger distance shows a more global gravity picture to the vehicles. The same rule can be applied to the altitude the twins are flying at. Currently, the Science Phase is expected to last 84 Days and end on May 29, 2012 after three mapping cycles have been completed. In between cycles, the Spacecraft will make small maneuvers to fine-tune their orbits. The extended mission phase that would lead to more mapping cycles is still under evaluation by the Science Team. No official word has been given yet and teams are working according to the pre-planned mission timeline that shows final mission termination in July. For more on the GRAIL Mission Timeline, click here.
The two spacecraft are currently in a polar, near circular orbit around the Moon with a mean altitude of 54.5 Kilometers. GRAIL-B, also called Flow, is leading the convoy as planned because the instrument construction requires GRAIL-A – or Ebb – to trail behind the other twin so that Science Data can be gathered. Over the course of the Science Phase, the orbit and distance between the Spacecraft will change as scientists want a full picture of the gravitational field of the Moon. Close range lets the spacecraft detect local gravity elements while a bigger distance shows a more global gravity picture to the vehicles. The same rule can be applied to the altitude the twins are flying at. Currently, the Science Phase is expected to last 84 Days and end on May 29, 2012 after three mapping cycles have been completed. In between cycles, the Spacecraft will make small maneuvers to fine-tune their orbits. The extended mission phase that would lead to more mapping cycles is still under evaluation by the Science Team. No official word has been given yet and teams are working according to the pre-planned mission timeline that shows final mission termination in July. For more on the GRAIL Mission Timeline, click here.
GRAIL-A returns first Video of the Moon
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February 2, 2012
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_
The first Video taken by the one of the cameras aboard the GRAIL Spacecraft that are part of the MoonKAM Education and Public Outreach Program has been released by NASA. GRAIL-A or ‘Ebb’ acquired the footage during the Checkout of the MoonKAM Payload on January 19, 2012. The short video clip shows the far side of the Moon as the vehicle flies from the north to the south pole. The video is showing remarkable detail of the lunar surface including craters and lunar maria like Mare Orientale, a 900-kilometer impact basin on both the Moon's near and far side. MoonKAM on GRAIL-B (‘Flow’) will be tested later in the mission. The GRAIL Mission is currently in its Period Reduction Phase – adjusting the Orbits of the twin Spacecraft from 11.5-hour highly elliptical orbits to 113-minute circular orbits. GRAIL-A has completed its second cluster of Engine Burns on January 28 and is now in an approximately 37 by 86-Kilometer Orbit (23 by 54 Miles). |
_GRAIL-B is currently making its second
round of Period Reduction Maneuvers seeking to place it in a orbit that will last
3 minutes longer than GRAIL-A’s. From that point on, the Mission Enters its next
Phase, the Transition to Science Phase. In order to begin the science phase, the position
of each vehicle relative to the other has to be calculated and precisely
adjusted. At the start of this phase, GRAIL- is flying higher than A. This
situation enables engineers to perform maneuvers in a timed manner to organize
the spacecraft correctly. A complicated series of rendezvous maneuvers will be
flown to reach the initial separation distance with GRAIL-B leading the ‘convoy’.
The next Mission Phase Transition is planned for February 6.
GRAIL A&B get new Names while adjusting their Orbits
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January 17, 2012
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_ NASA’s
GRAIL Mission is progressing as expected as the twin Spacecraft are in the
middle of their crucial Period Reduction Phase to adjust their respective
orbits around the Moon. The Orbit Adjust Phase started 15 Days ago on January 2, 2012. Each of the Spacecraft have
conducted three Period Reduction Maneuvers to get into lower orbits. GRAIL-A
made its first orbit adjustment burns on January 6 and 7. GRAIL-B followed one
week later and also made three successful engine firings. The MR-106L Main Engines of the individual spacecraft consumed more fuel during these maneuvers than during the large Lunar Orbit Insertion Burns that took
place on December 31, 2011 and January 1, 2012. Currently, GRAIL-A is in a
3.7-hour orbit while GRAIL-B is somewhat higher in a 3.9-hour orbit. Both
spacecraft started with an orbital period of 11.5 hours. GRAIL-A is in a 93 by
1,990-Kilometer Orbit (57.8 x 1,237 Miles) – GRAIL-B in a 108.8 by
2,173-Kilometer Orbit (67.5 x 1,350.4 Miles). Four or more Period Reduction
Maneuvers remain for each of the orbiters to precisely adjust their trajectories
placing them into identical orbits at an altitude of 55 Kilometers (34mi) above
the lunar surface. The Phase will continue until February 6 when the Mission
enters its Transition to Science Phase.
|
_Meanwhile, the Student Contest to name the GRAIL
Spacecraft came to a close and NASA anncounced the new names earlier today.
More than 900 Schools from 45 States participated in the contest. The winning
school is Emily Dickenson Elementary in Bozeman, Montana. GRAIL-A has been
named ‘Ebb’ and GRAIL-B’s new name is ‘Flow’ – reflecting the effect the Moon
has on every-day life here on Earth. The winner of the contest, a 4th grade class at Emily Dickinson
Elementary, will have the privilege of taking the first images of the Moon using
the MoonKam Payload aboard the GRAIL Orbiters.
GRAIL-B in Lunar Orbit and in good Health
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January 1, 2012
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_
Both GRAIL
Orbiters are in Orbit around the Moon after the second Twin, GRAIL-B, completed
its Lunar Orbit Insertion Maneuver today following Spacecraft A that inserted
itself 25 hours earlier on Dec 31.
GRAIL-B was trailing behind its twin since October when a Course Correction Maneuver caused the Orbiter’s ways to part in order to set up this LOI Interval. This has been done to give Mission Controllers and NASA’s Deep Space Network the opportunity to focus on one Spacecraft at a time. Commands for the complex LOI Maneuver had been linked up to GRAIL-B via Deep Space Network Assests several days ago when final trajectory analyses were complete. The execution of these commands started prior to Main Engine Ignition with a Re-Orientation Maneuver. GRAIL-B used its Attitude Control System to make the maneuver to the proper orientation for the LOI Burn. Two Minutes before the scheduled start time, the vehicle was in position for the Burn. At 22:05 GMT (5:05pm EST), the MR-106L Main Engine ingited for a 37.8-Minute Burn to slow the vehicle down just enough so it would enter a highly elliptical orbit. During the Burn, all Vehicle Parameters stayed within limits and the Burn was completed as expected. At 22:44 GMT, the Engine shut down and Mission Personnel quickly announced that the Spacecraft was in a nominal orbit. The LOI Procedure slowed GRAIL-B down by 691 Kilometers per Hour (430mph or 192 Meters per Second). GRAIL-B completed a System Status Poll and Vehicle Health was determined to be pristine. |
_Two healthy vehicles are now in Orbit around the
Moon which means that one crucial Mission Objective has been completed and
teams are one step closer to obtaining never before seen gravitational data
from our nearest neighbor in the Solar System. Inside the Control Center at NASA's Jet Propulsion Laboratory, Congratulations were exchanged between Mission Controllers that spent their New Year's Celebration inside the GRAIL Control Room watching over GRAIL's Systems. Now with both Orbiters where they are supposed to be, teams will have a little breathing room to celebrate the new year and the accomplishments of the past two days.
With both Spacecraft successfully injected into Lunar Orbit, the Mission can proceed to its next Phase. The formal Mission Phase Transition to the Period Reduction Phase, also called Orbit Adjust Phase, is going to take place tomorrow. Over period of several weeks, each of the GRAIL Vehicles will make seven or more maneuvers to change their respective orbits around the Moon. Currently, their Orbits are elliptical with a period of about 11.5 hours. These Orbits will be re-shaped to circular ones that have a duration of only 113 minutes. Once the Orbits are finely tuned, the Mission Team will face the next challenge of placing both Spacecraft into identical Orbits with GRAIL-B in leading the ‘convoy’. Also over that period, activations and checkouts of the Science and Communications Equipment will commence to prepare the Orbiters for data acquisition. All Orbit Operations have to be complete by March 8 for the Science Phase of the Mission to start. A full Flight Plan for the GRAIL Mission can be found on our Mission Design Site.
Videos: GRAIL LOI from Mission Control
With both Spacecraft successfully injected into Lunar Orbit, the Mission can proceed to its next Phase. The formal Mission Phase Transition to the Period Reduction Phase, also called Orbit Adjust Phase, is going to take place tomorrow. Over period of several weeks, each of the GRAIL Vehicles will make seven or more maneuvers to change their respective orbits around the Moon. Currently, their Orbits are elliptical with a period of about 11.5 hours. These Orbits will be re-shaped to circular ones that have a duration of only 113 minutes. Once the Orbits are finely tuned, the Mission Team will face the next challenge of placing both Spacecraft into identical Orbits with GRAIL-B in leading the ‘convoy’. Also over that period, activations and checkouts of the Science and Communications Equipment will commence to prepare the Orbiters for data acquisition. All Orbit Operations have to be complete by March 8 for the Science Phase of the Mission to start. A full Flight Plan for the GRAIL Mission can be found on our Mission Design Site.
Videos: GRAIL LOI from Mission Control
GRAIL-A enters Lunar Orbit
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January 1, 2012
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_
The first of the twin GRAIL Spacecraft has successfully entered Lunar Orbit on New Year’s Eve. GRAIL-A is now orbiting our nearest neighbor while GRAIL-B is still blazing through space to reach its target later today.
GRAIL-A began the Lunar Orbit Insertion Phase on December 28. Commands for the complicated maneuver were linked up to the spacecraft days before their execution. Just after 21:00 GMT (4pm EST), GRAIL-A changed its orientation to the LOI Attitude in preparation for Ignition. The 40-minute Main Engine Burn started on time at 21:21 GMT and GRAIL slammed on the brakes to achieve Orbit. During the long Burn, Vehicle Telemetry was provided by NASA’s Deep Space Network Stations in Goldstone, California and Madrid, Spain. With its engine firing, the Spacecraft had its first close approach to the Lunar Surface passing the Lunar South Pole at an Altitude of just over 100 Kilometers. The Spacecraft performed flawlessly and all vehicle parameters were nominal throughout the burn. Shutdown came on time and shortly thereafter, Confirmation that the Spacecraft entered Orbit was given. The LOI Burn slowed GRAIL-A down by 688 Kilometers per Hour (427mph). Afterwards, the vehicle returned to its normal orientation with its Solar Arrays pointing at Sun. Mission Personnel conducted a vehicle status check and got positive results making sure that the Orbiter was in good condition after the Burn.
GRAIL-A is in a 90 by 8,363-Kilometer Orbit (56x5,197 Miles) with a period of about 11.5 hours.
Maria Zuber, GRAIL’s Principal Investigator, said, "My resolution for the new year is to unlock lunar mysteries and understand how the moon, Earth and other rocky planets evolved. Now, with GRAIL-A successfully placed in orbit around the moon, we are one step closer to achieving that goal."
GRAIL-B is on course and getting ready for its Lunar Orbit Insertion Burn that is planned to start at 22:05 GMT (5:05pm EST) today. Live - real time - coverage of the Event will come via our GRAIL Twitter Profile: @GRAIL_101
The first of the twin GRAIL Spacecraft has successfully entered Lunar Orbit on New Year’s Eve. GRAIL-A is now orbiting our nearest neighbor while GRAIL-B is still blazing through space to reach its target later today.
GRAIL-A began the Lunar Orbit Insertion Phase on December 28. Commands for the complicated maneuver were linked up to the spacecraft days before their execution. Just after 21:00 GMT (4pm EST), GRAIL-A changed its orientation to the LOI Attitude in preparation for Ignition. The 40-minute Main Engine Burn started on time at 21:21 GMT and GRAIL slammed on the brakes to achieve Orbit. During the long Burn, Vehicle Telemetry was provided by NASA’s Deep Space Network Stations in Goldstone, California and Madrid, Spain. With its engine firing, the Spacecraft had its first close approach to the Lunar Surface passing the Lunar South Pole at an Altitude of just over 100 Kilometers. The Spacecraft performed flawlessly and all vehicle parameters were nominal throughout the burn. Shutdown came on time and shortly thereafter, Confirmation that the Spacecraft entered Orbit was given. The LOI Burn slowed GRAIL-A down by 688 Kilometers per Hour (427mph). Afterwards, the vehicle returned to its normal orientation with its Solar Arrays pointing at Sun. Mission Personnel conducted a vehicle status check and got positive results making sure that the Orbiter was in good condition after the Burn.
GRAIL-A is in a 90 by 8,363-Kilometer Orbit (56x5,197 Miles) with a period of about 11.5 hours.
Maria Zuber, GRAIL’s Principal Investigator, said, "My resolution for the new year is to unlock lunar mysteries and understand how the moon, Earth and other rocky planets evolved. Now, with GRAIL-A successfully placed in orbit around the moon, we are one step closer to achieving that goal."
GRAIL-B is on course and getting ready for its Lunar Orbit Insertion Burn that is planned to start at 22:05 GMT (5:05pm EST) today. Live - real time - coverage of the Event will come via our GRAIL Twitter Profile: @GRAIL_101
Artist's Concept of GRAIL-A during LOI
GRAIL enters its Lunar Orbit Insertion Phase
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December 28, 2011
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_ NASA’s twin
GRAIL Spacecraft are on their final leg on a long trajectory to the Moon. The
Mission transitioned to its Lunar Orbit Insertion Phase today that sets the
stage for actual Lunar Orbit Insertion taking place on December 31 and January
1.
Ending its cruise phase that was 108 Days in duration and included several trajectory correction maneuvers for each spacecraft, both Orbiters are now gearing up for entering Lunar Orbit. For LOI (Lunar Orbit Insertion), each GRAIL Spacecraft will make its final approach to the Moon on a path taking it close to the Lunar South Pole. Then, a 40-minute engine burn will be conducted by GRAIL-A (39 Minutes for GRAIL-B) to slow down the Spacecraft by 688 Kilometers per Hour (427mph), 691kph (430mph) respectively, in order to achieve lunar orbit. GRAIL-A will make its LOI Burn at 21:21 GMT (4:21pm EST) on December 31. Just under 25 hours later, GRAIL-B will start its Maneuver to insert itself into Lunar Orbit. The second Maneuver is planned for January 1 at 22:05 GMT (5:05pm EST). This 25-hour interval gives Mission Personnel and Deep Space Network Tracking Stations the opportunity to focus on one Spacecraft at a time. |
GRAIL Cruise Trajectory
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_Two DSN Antennas will be pointed towards the Moon to
provide Data from the Spacecraft making their respective Maneuvers. Both,
Madrid and Goldstone, will be providing data to have a redundant data link
during the crucial maneuver that will be autononously conducted by the
vehicles. Commands for the Insertion Burn have already been uplinked to the Spacecraft and are ready for execution by the on-board computers. Mission Controllers will be watching data coming from the Orbiters and will be ready to take action should any off-nominal telemetry occur during LOI.
The initial Orbits of the Spacecraft will be highly elliptical and have a period of 11.5 hours. Also, the orbits of each GRAIL Spacecraft will be different from one another. Over a period of two months, each GRAIL Vehicle will perform up to 7 maneuvers to reduce its orbital period. Also during that period, the orbits will be reshaped so that the two Spacecraft are in identical orbits flying in formation at a distance of about 100 Kilometers that will vary as the mission progresses.
The initial Orbits of the Spacecraft will be highly elliptical and have a period of 11.5 hours. Also, the orbits of each GRAIL Spacecraft will be different from one another. Over a period of two months, each GRAIL Vehicle will perform up to 7 maneuvers to reduce its orbital period. Also during that period, the orbits will be reshaped so that the two Spacecraft are in identical orbits flying in formation at a distance of about 100 Kilometers that will vary as the mission progresses.
|
_
The targeted orbit is an extremely low and
circular trajectory around the moon with a period of 113 Minutes. On March 8,
2012, the 82-day Science Phase of the Mission is planned to begin with two spacecraft
orbiting in perfect formation. Three mapping cycles will be completed - each with
different ranges between the vehicles and different orbital altitudes to cover
the Moon three times and focussing on different Depth Profiles on the
respective cycles. By the end of May, the Primary Mission of the GRAIL Vehicles
will be over. A short decommissioning period will set the Mission up for Lunar
Impact about 40 days after the final Phase of the Flight. Currently, Mission
Teams are evaluating the possibility of extending the Mission until December
2012 should the Spacecraft survive a Lunar Eclipse on June 4, 2012. The extended Mission would be used to take the Orbiters to an even lower altitude and map fine gravitational properties to further improve knowledge of the Lunar Interior. For that, maneuvers would be conducted to increase chances of the Spacecraft surviving the eclipse. However this is still under evaluation by mission personnel.
|
_ As of 19:00 GMT today,
GRAIL-A was 107,300 Kilometers (66,700 Miles) from the Moon flying at a
relative velocity of 1,205kph (749mph) while GRAIL-B was 128,800km (80,000mi)
from its target moving at a relative speed of 1,240kph (771mph). 23,900
Kilometers (14,850 Miles) were between the two Orbiters at this time.
Both Spacecraft have been checked out during the Cruise Phase and are operating normally as of today.
More on GRAIL’s Mission Design can be found on our Mission Design and Timeline Site.
Both Spacecraft have been checked out during the Cruise Phase and are operating normally as of today.
More on GRAIL’s Mission Design can be found on our Mission Design and Timeline Site.
First Trajectory Control Maneuvers completed
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October 7, 2011
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Both GRAIL Spacecraft are continuing their mission as planned and are in the middle of their long cruise phase to the Moon. About 81 days remain until the Lunar Orbit Insertion Phase begins. The actual LOI Maneuvers will occur on December 31, 2011 and January 1, 2012 when the spacecraft arrive at the Moon 25 hours apart to perform their respective engine burns.
According to the mission team, no anomalies have been noted up to this point in the mission. Both orbiters are performing well and instruments have checked out to be in good health as well.
GRAIL-A performed its first large Trajectory Control Maneuver on September 30 at 2pm EDT. The 127-second Main Engine Burn was nominal and changed the velocity of the vehicle by 31.3mph. GRAIL-B’s first Correction Maneuver was also nominal. It was performed on October 5, at 2pm EDT and provided a change in velocity of 56.1mph. The burn had a duration of 3 minutes and 54 seconds.
Those burns are used to keep the course of each individual spacecraft fine-tuned in order to reach the exact LOI target. Also, this first burn for the Orbiters verified that the engine of the spacecraft is in good shape and ready to execute the major burn to place GRAIL into Lunar Orbit. More Burns are coming up until LOI and those will be executed as needed. An earlier opportunity to perform an initial TCM was waived because the course of the orbiters was in proper shape since the Launch Vehicle placed the spacecraft on a very exact path. A basic schedule of Mission Events can be found here.
According to the mission team, no anomalies have been noted up to this point in the mission. Both orbiters are performing well and instruments have checked out to be in good health as well.
GRAIL-A performed its first large Trajectory Control Maneuver on September 30 at 2pm EDT. The 127-second Main Engine Burn was nominal and changed the velocity of the vehicle by 31.3mph. GRAIL-B’s first Correction Maneuver was also nominal. It was performed on October 5, at 2pm EDT and provided a change in velocity of 56.1mph. The burn had a duration of 3 minutes and 54 seconds.
Those burns are used to keep the course of each individual spacecraft fine-tuned in order to reach the exact LOI target. Also, this first burn for the Orbiters verified that the engine of the spacecraft is in good shape and ready to execute the major burn to place GRAIL into Lunar Orbit. More Burns are coming up until LOI and those will be executed as needed. An earlier opportunity to perform an initial TCM was waived because the course of the orbiters was in proper shape since the Launch Vehicle placed the spacecraft on a very exact path. A basic schedule of Mission Events can be found here.
Both GRAIL Spacecraft in good Shape after first Look |
September 12, 2011 |
After launching on September 10, both GRAIL Spacecraft have already made their first mission phase transition which is only a formal one that does not involve much spacecraft reconfiguration. The Mission transitioned from a 24-hour launch phase to a Cruise Mode of ~109 Days until December 28, 2011 prior to their arrival at the Moon.
GRAIL A and B are both power positive, meaning that their solar arrays deployed as planned and are providing power to the spacecraft and its batteries. Having good solar cell deployment is essential for mission success and meeting mission objectives. Further vehicle status polls and health checks are still indicating that the twins are in good shape after leaving Earth on their Delta II 7920H-20 Launch Vehicle. Over the course of the next week, more checks will be performed to see if all systems are working as expected. Flight Controllers are also looking at the trajectories of the spacecraft. The first TCM (Trajectory Control Maneuver) for each individual orbiter is coming up soon. Timelines show it on Sep. 15 for GRAIL-A and Sep. 16 for B. Those dates are not set in stone and TCMs can be performed as needed. This first TCM is optional as it is only required when a spacecraft is off-course to a certain extent. This could happen when there is a small performance anomaly on second stage sutoff prior to Spacecraft Separation. Such an issue has not been noted. Both trajectories will be analyzed carefully to determine if a Burn of GRAIL’s Engine is needed. There are a total of 5 TCMs that are planned for each GRAIL prior to the big Lunar Orbit Insertion Burn.
GRAIL A and B are both power positive, meaning that their solar arrays deployed as planned and are providing power to the spacecraft and its batteries. Having good solar cell deployment is essential for mission success and meeting mission objectives. Further vehicle status polls and health checks are still indicating that the twins are in good shape after leaving Earth on their Delta II 7920H-20 Launch Vehicle. Over the course of the next week, more checks will be performed to see if all systems are working as expected. Flight Controllers are also looking at the trajectories of the spacecraft. The first TCM (Trajectory Control Maneuver) for each individual orbiter is coming up soon. Timelines show it on Sep. 15 for GRAIL-A and Sep. 16 for B. Those dates are not set in stone and TCMs can be performed as needed. This first TCM is optional as it is only required when a spacecraft is off-course to a certain extent. This could happen when there is a small performance anomaly on second stage sutoff prior to Spacecraft Separation. Such an issue has not been noted. Both trajectories will be analyzed carefully to determine if a Burn of GRAIL’s Engine is needed. There are a total of 5 TCMs that are planned for each GRAIL prior to the big Lunar Orbit Insertion Burn.
GRAIL Takes off to the Moon |
September 10, 2011; 11am EDT |
60 Minutes to T-0 |
September 10, 2011; 7:29am EDT |
Countdown
activities this morning at Space Launch Complex 17 are progressing very well and
are on schedule at the L-1 Hour mark.
Powerup of the Delta rocket was completed prior to L-4 and went smoothly. The countdown started with a planned 60-minute hold at the T-2:30 mark. Terminal Countdown Polls were taken and all stations reported GO to press into Terminal Count on time at 5:29:45am EDT. Major activities included pressurization of the Nitrogen and Helium storage tanks aboard the Delta Rocket and the activation of the RIFCA (Redundant Inertial Flight Control Assembly) that provides processing capabilities for guidance, navigation, flight controls and mission sequencing data. RP-1 Loading began at 5:55am EDT. 9,989 gallons of refined Kerosene were tanked in 19 minutes and 5 seconds. Liquid Oxygen tanking followed at 6:46am EDT. The 25-minute process ended on time. The LOX Tank was topped off to 100% for pressurization test. When that was successfully completed, LOX was dumped to the 95% level. Decay checks on the He and N2 systems were performed and returned nominal results. Next up are Engine Slew Tests on all of the engines. |
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The weather situation looks better than on GRAIL’s previous launch attemtps on Thursday. Forecasters have issued a 80% chance of favorable weather for today’s opportunitities. Concerns are thick clouds as well as cumulus clouds and flight through precipitation. Showers in the vicinity of SLC-17 will not be a concern. Upper Level Winds have been within limits for a large part of the countdown, however RED conditions are currently observed for winds at 0-25,000 feet. Meteorologists will continue to evaluate Weather Balloon Data. Satellite and Radar Data show some activity to the west. Lightning strikes have been recorded. The structures are quickly dissipating after making landfall, so that this system will not be of concern as of now. Space Weather is also rather benign.
The Antigua Ground Station is still facing a Tropical Storm and had to perform intial securing operations. One of two satellite dishes has already been stowed. Should Antigua not be available today, Downrange Communication capabilities will be provided by the TRDSS. Tracking stations further downrange have reported readiness for mission operations. NASA's Deep Space Network is also ready to support the mission.
The Antigua Ground Station is still facing a Tropical Storm and had to perform intial securing operations. One of two satellite dishes has already been stowed. Should Antigua not be available today, Downrange Communication capabilities will be provided by the TRDSS. Tracking stations further downrange have reported readiness for mission operations. NASA's Deep Space Network is also ready to support the mission.
MST rolled back for Launch |
September 10, 2011; 3am EDT |
The Delta II with the twin GRAIL Spacecraft on top of it has been revealed as the Mobile Service Tower was rolled back tonight in preparation for today’s lifoff. Launch is planned for 8:29 or 9:08am EDT. Rolling the Tower occurred without any issues and the Delta Rocket is in good shape for today’s liftoff.
Once again, the weather will be the focus of attention today. Weather Balloons will be released periodically starting at 3:29am EDT. Expected shortly is the confirmation of successful launch pad and MST closeouts in preparation for putting up roadblocks and vacating SLC-17 prior to tanking which should pick up with RP-1 fueling at 5:49am EDT. LOX Loading should begin 55 minutes later. No technical problems have been reported up to this point.
At this time, the launch team is starting their shift on console as well.
Once again, the weather will be the focus of attention today. Weather Balloons will be released periodically starting at 3:29am EDT. Expected shortly is the confirmation of successful launch pad and MST closeouts in preparation for putting up roadblocks and vacating SLC-17 prior to tanking which should pick up with RP-1 fueling at 5:49am EDT. LOX Loading should begin 55 minutes later. No technical problems have been reported up to this point.
At this time, the launch team is starting their shift on console as well.
GRAIL&Delta II cleared for Weekend Launch |
September 9, 2011; 3pm EDT |
GRAIL is clear to launch on one of two attempts tomorrow from SLC-17 at Cape Canaveral Air Force Station.
Managers met today to discuss an anomaly that was observed during detanking after the first launch attempts were scrubbed on Thursday. A heater that is part of the propulsion system stayed on longer than usual causing equipment to exceed red line limits slightly. It was only a minor issue, but managers wanted to give the team additional time to fully understand the situation and make completely sure that no equipment was harmed in the changed thermal environment. The meeting concluded with a decision to press on with launch operations for Saturday. Launch Times:
Weather conditions look better than they did on Thursday. Forecasters have issued a 60% chance of good weather with some concerns. The primary focus will be on cumulus clouds and flight through precipitation. Weather at the Antigua ground station is expected to show the first traces of Tropical Storm Maria, but teams anticipate that the station will be up and running. If that is not the case, communication with the vehicle can be provided by Florida Ground Stations and the Tracking and Data Relay Satellite System. The Launch Team will come in just before 3am EDT and the Mobile Service Tower will be rotated earlier (weather permitting). Countdown timelines show that at around 11pm EDT. Check out the Launch Info Page for updated Countdown Timelines, more Weather Info and Links to Ascent Data&Ground Track. |