Updates MESSENGER Mission News

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MESSENGER Mission News
October 15, 2008
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MESSENGER Gains Speed

Shortly after 4 a.m. this morning, MESSENGER reached its greatest speed relative to the Sun. The spacecraft, nearly 70% closer to the Sun than Earth, was traveling nearly 140,880 miles per hour (62.979 kilometers per second) relative to the Sun. At this speed MESSENGER would traverse the distance from Earth to Earth’s Moon in only 1.7 hours!

Even at this great speed MESSENGER is slightly slower than the fastest spacecraft: Helios 2. That spacecraft – launched into a solar orbit on January 15, 1976 – reached a top speed of 157,078 miles per hour (70.220 kilometers per second) relative to the Sun in April of 1976.
Because of MESSENGER’s near-perfect Mercury flyby trajectory on October 6, the mission design and navigation team decided that a trajectory-correction maneuver (TCM) scheduled for October 28 will not be needed. The next maneuver for the mission, scheduled to be carried out in two parts on December 4 and December 8, will re-target the spacecraft for the third and final encounter with Mercury in just under a year on September 29, 2009.

New Color Images of Mercury Available

The MESSENGER Science Team has released five new images from the probe’s second flyby of Mercury. To the human eye, Mercury shows little color variation, especially in comparison with a colorful planet like Earth. But when images taken through many color filters – such as the 11 narrow-band color filters on the Mercury Dual Imaging System’s Wide Angle Camera (WAC) – are used in combination, differences in the properties of Mercury’s surface can create a strikingly colorful view of the innermost planet.

Here are four images of Mercury. The image in the top left is the previously released grayscale monochrome image taken with a single (430 nanometer) WAC filter; the remaining three images are three-color composites, produced by placing the same three WAC filter images with peak sensitivities at 480, 560, and 630 nanometers in the blue, green, and red channels, respectively. Shown here are two color images of Thākur, named for the Bengali poet, novelist, and Nobel laureate influential in the late 19th and early 20th centuries.

In both the optical navigation images and the full-planet WAC approach frame, a bright feature is clearly visible in the northern portion of the crescent-shaped Mercury. This Narrow Angle Camera (NAC) image resolves details of this bright feature, showing that it surrounds a small crater about 30 kilometers (19 miles) in diameter, seen nearly edge on.

This pair of images illustrates the dramatic effect that illumination and viewing geometry (i.e., the angle at which Sunlight strikes the surface, and the angle from which the spacecraft views the surface) has on the appearance of terrain on Mercury. And this NAC image, taken about 85 minutes after MESSENGER’s closest approach during the mission’s second Mercury flyby, shows a view of Astrolabe Rupes, named for the ship of the French explorer Jules Dumont d’Urville. Rupes is the Latin word for cliff.



Additional information and features from this encounter will be available online at http://messenger.jhuapl.edu/mer_flyby2.html, so check back frequently to see the latest released images and science results!

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

 

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The top one looks straight monochrome. NASA have a true colour picture from the January flyby:
It's color, but not true color. Read the corresponding text. They chose color filters that have scientific interests, not filters that match the primary colors of the human eye.

Anyway, I still think the "gray" Mercury is more realistic than the "brown" Mercury. "Gray" means there isn't much difference between the amplitude in different colors. If there isn't much difference between the colors they used, there probably isn't much difference either between the three colors of the human eye (which are closer to each other).

Do we now have a complete map of the surface of Mercury?
 

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For Immediate Release
October 29, 2008


Media Contact:
Paulette Campbell
(240) 228-6792
[email protected]
MESSENGER Reveals More “Hidden” Territory on Mercury

Gliding over the battered surface of Mercury for the second time this year, NASA’s MESSENGER spacecraft has revealed even more previously unseen real estate on the innermost planet, sending home hundreds of photos and measurements of its surface, atmosphere, and magnetic field.
The probe flew by Mercury shortly after 4:40 a.m. EDT on October 6, 2008, completing a critical gravity assist to keep it on course to orbit Mercury in 2011 and unveiling 30 percent of Mercury’s surface never before seen by spacecraft.
“The region of Mercury’s surface that we viewed at close range for the first time this month is bigger than the land area of South America,” says Sean Solomon, MESSENGER principal investigator and the director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. “When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95% of the planet.”
MESSENGER’s science instruments worked feverishly through the flyby – cameras snapped more than 1,200 pictures of the surface, while topography beneath the spacecraft was profiled with the laser altimeter. We have completed an initial reconnaissance of the solar system’s innermost planet, enabling us to gain a global view of Mercury’s geological history and internal magnetic field geometry for the first time,” Solomon continues.
The comparison of magnetosphere observations from MESSENGER’s first flyby in January with data from the probe’s second pass has provided key new insight into the nature of the planet’s internal magnetic field and revealed new features of Mercury’s magnetosphere.
“The previous flybys by MESSENGER and Mariner 10 provided data only on Mercury’s eastern hemisphere,” explains Brian Anderson, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. “The most recent flyby gave us our first measurements on Mercury’s western hemisphere, and with them we discovered that the planet’s magnetic field is highly symmetric.”
“This seemingly simple result is significant for the planet’s internal field because it implies that the dipole is even more closely aligned with the planet’s rotation axis than we could conclude before the second flyby,” says Anderson, who is deputy project scientist. “Even though the rigorous analyses of these data are ongoing, we expect that this result will allow us to limit the theories of planetary magnetic field generation to those that predict a strongly rotationally aligned moment.”
The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) observed the extended tail, night side, and day side regions of Mercury’s thin atmosphere – known as an exosphere – searching for emission from sodium, calcium, magnesium, and hydrogen atoms.
“The MASCS observations of magnesium are the first-ever detection of this species in Mercury’s exosphere,” explains MESSENGER participating scientist Ron Vervack of APL. Preliminary analysis of the sodium, calcium, and magnesium observations suggests that the spatial distributions of these three species are different and that the distribution of sodium during the second flyby is noticeably different from that observed during the first flyby.
“The spatial distributions of sodium, calcium, and magnesium are a reflection of the processes that release these species from Mercury’s surface,” Vervack adds. “Now that we were finally able to measure them simultaneously, we have an unprecedented window into the interaction of Mercury’s surface and exosphere.”
The probe’s Mercury Laser Altimeter (MLA) measured the planet’s topography, allowing scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images.
“During the last flyby, the Mercury Laser Altimeter acquired a topographic profile in a hemisphere of the planet for which there were no spacecraft images,” explains Maria Zuber, MESSENGER co-investigator and head of the Department of Earth, Atmospheric, and Planetary Sciences at the Massachusetts Institute of Technology. “During the second flyby, in contrast, altimetry was collected in regions where images from MESSENGER and Mariner 10 are available, and new images were obtained of the region sampled by the altimeter in January. These topographic measurements now improve considerably the ability to interpret surface geology.”
Now that MESSENGER’s cameras have imaged more than 80 percent of Mercury, it is clear that, unlike the Moon and Mars, the planet lacks hemispheric-scale geologic differences. “On the Moon, dark volcanic plains are concentrated on the near side and are nearly absent from the far side,” says MESSENGER co-investigator Mark Robinson of Arizona State University. “On Mars, the southern hemisphere consists of older, cratered highlands, whereas the northern hemisphere consists of younger lowlands. Mercury’s surface is more homogeneously ancient and heavily cratered, with large extents of younger volcanic plains lying within and between giant impact basins.”
Color imaging also shows that Mercury’s crust is compositionally heterogeneous. “Although definitive compositional interpretations cannot yet be made, the distribution of different components varies both across the surface and with depth – Mercury’s crust is more analogous to a marbled cake than a layered cake,” Robinson adds. “Once MESSENGER’s suite of science instruments returns a host of data from the orbital phase of the mission, compositions will be determined for the newly discovered color units.”
“The first two Mercury flybys have returned a rich dividend of new observations,” says Solomon. “But some of the observations we are most eager to make – such as the chemical make-up of Mercury’s surface and the nature of its enigmatic polar deposits – will not be possible until MESSENGER begins to orbit the innermost planet. Moreover, the very dynamic nature of Mercury’s interaction with its interplanetary environment has taught us that continuous observations will be required before we can claim to understand our most sunward sister planet.”



MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

The Applied Physics Laboratory, a division of the Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.


 

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MESSENGER Mission News
November 26, 2008
http://messenger.jhuapl.edu




Second Group of Mercury Craters Named

The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to name 15 craters on Mercury. All of the newly named craters were imaged during the mission’s first flyby of the solar system’s innermost planet in January 2008.
The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for craters on Mercury, all of the craters are named after famous deceased artists, musicians, or authors.
“We’re pleased that the IAU has again acted promptly to approve this new set of names for prominent craters on Mercury,” says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. “These latest names honor a diverse suite of some of the most accomplished contributors to mankind’s higher aspirations. They also make it much easier for planetary scientists to refer to major features on Mercury in talks and publications.”
The newly named craters include:


Amaral, after Tarsila do Amaral of Brazil, considered one of the leading Latin American modernist artists.

Dalí, after Salvador Dalí, a Spanish painter and leader of the Surrealist Movement.

Enwonwu, after sculptor and painter Benedict Chukwukadibia Enwonwu, the most renowned Nigerian artist of the 20th century.

Glinka, after Mikhail Glinka, a Russian composer considered to be the “father” of genuinely Russian music.

Hovnatanian, after Hakop Hovnatanian, an Armenian painter known for his portraits.

Beckett, after Clarice Beckett, recognized as one of Australia's most important modernist artists.

Moody, after Ronald Moody, a self-taught, Jamaica-born sculptor and painter who found success in mid-20th-century London and Paris.

Munch, after Edvard Munch, a Norwegian Symbolist painter, printmaker, and draftsman, perhaps most well-known for his painting The Scream.

Navoi, after Alisher Navoi, a 15th century Uzbek poet, considered by many to be the founder of early Turkic literature.

Nawahi, after Joseph Nawahi, a self-taught artist, lawyer, educator, publisher, member of the Hawaiian legislature for many years, and principal adviser to Hawaii’s Queen Lili'uokalani.

Oskison, after John Milton Oskison, a Cherokee author who served as editor and editorial writer for the New York Evening Post.

Poe, after Edgar Allan Poe, American poet, critic, editor, and author. Best known for his tales of mystery and the macabre.

Qi Baishi, after Qi Baishi, a renowned Chinese painter known for his whimsical water colors.

Raden Saleh, after Raden Saleh, a 19th century Javanese naturalist painter considered to be the first modern artist from what is now Indonesia.

Sher-Gil, after Amrita Sher-Gil, an eminent Indian painter, today considered an important female painter of 20th-century India.



“It was quite enjoyable to consider candidate names from among the world's most accomplished people in the arts and humanities,” says MESSENGER Participating Scientist Dave Blewett, of the Johns Hopkins University Applied Physics Laboratory, in Laurel, Md. “It's also gratifying to have the IAU approve names that have meaning to the team members. For example, the crater Poe (named for Edgar Allan Poe) was a popular choice, as he happens to be a local favorite because of his Baltimore ties.
“Having names for many of the prominent craters will help us to remember and discuss specific locations in this previously ‘undiscovered country,’” adds Blewett.
An image of Mercury showing the locations of the newly named features is available online at http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=276.
The addition of these craters, along with the 12 features named in April, brings the total to 27 newly named surface features for Mercury in 2008. In September 2009 MESSENGER will complete a third and final flyby of Mercury before becoming the first spacecraft to orbit the planet, beginning in March 2011.




MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
 
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MESSENGER Mission News
December 4, 2008
http://messenger.jhuapl.edu/


Deep-Space Maneuver Positions MESSENGER for Third Mercury Encounter

The Mercury-bound spacecraft MESSENGER completed the first part of a two-part deep-space maneuver today, providing the expected 90% of the velocity change needed to place the spacecraft on course to fly by Mercury for the third time in September 2009. A 4.5-minute firing of its bi-propellant engine increased the probe’s speed relative to the Sun by 219 meters per second (489 miles per hour) to a speed of about 30.994 kilometers per second (69,333 miles per hour).

MESSENGER was 237.9 million kilometers (147.8 million miles) from Earth when today’s maneuver began at 3:30 p.m. EST. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 13 minutes, 14 seconds later, when the first signals indicating spacecraft thruster activity reached NASA’s Deep Space Network tracking station outside Goldstone, Calif.

“It was a perfect maneuver,” said APL’s Eric Finnegan, MESSENGER Mission Systems Engineer. “Initial data analysis indicates an extremely accurate maneuver execution. After sifting through all the post-burn data I expect we will find ourselves right on target.” The remaining 10% of this deep-space-maneuver’s velocity change will be imparted to the spacecraft during the second part, which will occur on December 8, 2008. The total planned velocity change is 247 meters per second.

MESSENGER is travelling at 109,435 kilometers per hour (68,864 miles per hour) relative to the Sun. One final deep-space maneuver on November 29, 2009, will target the probe for Mercury orbit insertion in March 2011, making it the first spacecraft to orbit the planet closest to the Sun.



MESSENGER Web Tool Wins Association Award

The Association of Marketing and Communications Professionals (AMCP) has awarded the MESSENGER Mercury Flyby Visualization Tool a “Gold” award in the “Web interactive capabilities” category of its MarCom Awards, an international competition for marketing and communication professionals involved in the concept, writing and design of marketing and communication programs and print, visual and audio materials.

The Web-based tool, available at http://messenger.jhuapl.edu/encounters/, offers a unique opportunity to see simulated views of Mercury from MESSENGER’s perspective, during approach, flyby, and departure, or in real-time (as the observations actually occur).


MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
 

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A curious picture here, from the Planetary Society's blog:



MESSENGER's trip to Mercury requires a total of six gravity assists (one of Earth, two of Venus, and three of Mercury) to permit it to enter orbit at the small planet close to the Sun. This animation shows that journey and the motions of Venus and Mercury using a frame of reference that holds the Earth-Sun line fixed. The maneuver I'm talking about in this blog entry is the one labeled "DSM-4" on the orbit diagram and timeline.

Credit: NASA / JHUAPL / Carnegie Institution of Washington
 

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MESSENGER Mission News
December 8, 2008
http://messenger.jhuapl.edu/


MESSENGER Completes Two-Part Maneuver; Poised for Third Mercury Encounter

MESSENGER completed the second part of a two-part deep-space maneuver today, providing the remaining 10% velocity change needed to place the probe on course to fly by Mercury for the third time in September 2009.

Unlike most maneuvers, this one was conducted in a so-called “open loop,” explained MESSENGER Project Manager Peter Bedini. “In closed-loop maneuvers, the accelerometers are used to trim the burn, and thrusters are employed as needed to adjust the direction as perceived by the accelerometers,” said Bedini, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. “To test the unlikely scenario that we will not have accelerometer data for the huge Mercury orbit insertion, we did this second part without using those data as feedback.”

The first part of the maneuver, which occurred on December 4, increased the probe’s speed relative to the Sun by 219 meters per second (489 miles per hour) to about 30.994 kilometers per second (69,333 miles per hour). Today’s maneuver, which began at 3:30 p.m. EST, increased MESSENGER’s speed by an additional 24.7 per second, for a total velocity change of 247 meters per second. Mission controllers at APL verified the start of the maneuver about 13 minutes, 18 seconds later, when the first signals indicating spacecraft thruster activity reached NASA’s Deep Space Network tracking station in Canberra, Australia.

“We are now on target for the third Mercury flyby next September,” Bedini said. “The fifth deep-space maneuver two months later will position MESSENGER for Mercury orbit insertion in March 2011,” enabling it to become the first spacecraft to orbit the innermost planet.



MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
 

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MESSENGER Mission News
December 23, 2008
http://messenger.jhuapl.edu/




MESSENGER Approaches Three Billion Miles, Enters Fourth Solar Conjunction

On December 26, the MESSENGER spacecraft will have traveled three billion miles since its launch, marking somewhat more than 60 percent of the probe’s journey toward its destination to be inserted into orbit about Mercury.

“That MESSENGER’s odometer reading has reached another major milestone reminds us of the long and complex route that our spacecraft must follow,” offers Principal Investigator Sean Solomon, of the Carnegie Institution of Washington “The year now ending has seen the first two spacecraft flybys of the innermost planet in more than three decades, encounters that have yielded a rich lode of new observations. The journey is far from over, but MESSENGER has a skilled team to guide it the rest of the way.”

Mercury orbits deep within the Sun’s gravity well. So, even though the planet can be as close as 82 million kilometers (51 million miles) from Earth, getting the probe into orbit around Mercury depends on an innovative trajectory using the gravity of Earth, Venus, and Mercury itself to slow and shape the probe's descent into the inner solar system. On its 4.9 billion-mile journey to becoming the first spacecraft to orbit the planet Mercury, MESSENGER has flown by Earth once, Venus twice, and Mercury twice. Still to come is one more flyby of Mercury in late September 2009.

Today the spacecraft entered its fourth superior solar conjunction of the mission, placing it on the opposite side of the Sun from Earth. (To see where MESSENGER is now, visit http://messenger.jhuapl.edu/whereis/index.php.) The Sun-Earth-probe angle will be between 2° and 3° until January 6, 2009, so during the next two weeks there will be no communication with the spacecraft.

To support the conjunction period, the MESSENGER team performed several activities to prepare the spacecraft and keep it safe, explains MESSENGER Mission Operations Manager Andy Calloway. Examples include extension of the onboard command detection timer and inclusion of attitude alternations to avoid an autonomous propulsive burn to unload spacecraft angular momentum. In addition, all instruments have been turned off except for the Gamma-Ray Spectrometer sensor, which will remain in a maintenance mode to control closely the temperature of its cryogenic cooler.

“The team will gather for a spacecraft health assessment on the first contact after the conjunction, and then the payload will be powered on again, timers will be restored, and nominal operations will resume,” says Calloway, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “The next superior solar conjunction lasts only five days – from June 6 to June 10 – and will therefore not require such extensive preparations.” The next long conjunction spans about two weeks beginning on November 2, 2009.

The MESSENGER spacecraft is a little more than two years from reaching its final destination, but the mission Science Team has been collecting data and sharing it with the larger scientific community. Those plans and results are available online at http://messenger.jhuapl.edu/soc/index.html.



MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
 

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MESSENGER Continues Hunt for Ever-Elusive Vulcanoids

MESSENGER reaches its orbital perihelion today and passes within 0.31 astronomical units (AU) of the Sun (one AU is nearly 150 million kilometers or 93 million miles). The mission’s imaging team is taking advantage of the probe’s proximity to the fiery sphere to continue their search for vulcanoids – small, rocky asteroids that have been postulated to circle the Sun in stable orbits inside the orbit of Mercury.

Vulcanoids are named after Vulcan, a planet once proposed to explain unusual motions in Mercury’s orbit. Scientists have long suspected that these small, faint “space rocks” exist. There is a gravitationally stable region between the orbit of Mercury and the Sun, which means that any objects that originally formed there could have remained for billions of years and might still be there today. All other such regions in the solar system are occupied by some type of debris (e.g., Trojan asteroids at stable points along the orbits of Jupiter and Neptune and Kuiper Belt objects near and beyond the orbit of Pluto).

The so-called vulcanoid region between the orbit of Mercury and the Sun is the main gravitationally stable region that is not known to be occupied. The region is, however, the most difficult to observe. Any vulcanoids would be difficult to detect from Earth because of the strong glare of the Sun. Previous vulcanoid searches have revealed no bodies larger than 60 kilometers in diameter. But MESSENGER’s travels in near-Mercury space enable a search for vulcanoids from a vantage never before attempted, says MESSENGER Science Team Member Clark Chapman, who is spearheading the team’s search along with his associate, William Merline.

“With MESSENGER, we can search for vulcanoids as small as 15 kilometers across,” said Chapman, a senior scientist at the Southwest Research Institute in Boulder, Colorado. Between February 7 and 11, the wide-angle camera of MESSENGER’s Mercury Dual Imaging System will have snapped 256 images in the areas east and west of the Sun. Because of the danger of the Sun’s glare, the camera will have to peek just past the probe’s sunshade to capture images.

“We are making the same observations on each day,” MESSENGER team member Nancy Chabot explained. “This cadence will allow us to reject cosmic rays and to distinguish, by its motion, the class of each object imaged” (e.g., vulcanoid vs. near- or inner-Earth asteroid).

The team carried out a similar imaging campaign over a nine-day period in June 2008, capturing 240 images of the outer portions of the would-be vulcanoid belt. “This sequence was designed to refine our observing techniques, assess limiting magnitudes, verify detectability of known objects, and make an initial search,” Chapman explained.

“Vulcanoids, should they be found, may provide scientists with insights into the conditions prevalent in the early solar system,” Chapman said. “In particular, if they exist or once existed, they would represent an additional population of impactors that would have cratered no other planet but Mercury, implying that the geological processes on Mercury have happened more recently than we would calculate if we assumed that Mercury’s craters formed at rates equivalent to cratering on the Moon and Mars.”

If vulcanoids are found not to exist, then we could be more confident that most of Mercury’s volcanic plains formed billions of years ago, as on the Moon, according to Chapman. The absence of vulcanoids would also focus scientists’ thinking on why vulcanoids never formed or, if they did form, why they are no longer there.


MESSENGER Thermal Engineer Maintains Cool in Extreme Environs

The Mercury-bound MESSENGER spacecraft will be assaulted by temperatures as high as 700°F as it orbits the planet closest to the Sun, and the only thing that will stand between its room-temperature science instruments and the blistering heat is a handmade ceramic-cloth quilt just one-quarter of an inch thick. Carl Jack Ercol, the man largely responsible for making sure that MESSENGER will be able to stand up to such harsh heat once imagined he’d make his living in a darker, much cooler environment: the coal mining industry. Read more about Ercol at http://messenger.jhuapl.edu/who_we_are/member_focus.html.



MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
 

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Anyway, I still think the "gray" Mercury is more realistic than the "brown" Mercury.
I'm confused.
Mercury has been portrayed as brown in many publications, including Orbiter, yet grey in others.
What is the true colour of Mercury?
 

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Sad news.

MESSENGER Mission News
March 20, 2009
http://messenger.jhuapl.edu



MESSENGER Team Remembers Dr. Mario H. Acuña

Mario H. Acuña, a senior astrophysicist at NASA Goddard Space Flight Center and Co-Investigator on the MESSENGER mission, died on March 5, 2009, after a long battle against multiple myeloma. During his four decades at NASA, he played a critical role in many NASA endeavors, serving as principal investigator or key developer of experiments flown on more than 30 missions to every planet in the solar system, as well as the Sun.

Acuña had been involved in the MESSENGER from its inception, 13 years ago. “He became an enthusiastic participant as soon as I mentioned MESSENGER to him, when it was just an idea without an acronym,” notes Stamatios M. Krimigis,chair of MESSENGER’s Atmosphere and Magnetosphere Group. “His deep technical knowledge and scientific insight, coupled with his absolute honesty and integrity made him an indispensable member of any technical review and a critical player when hard decisions had to be made.”

Acuña contributed to the development of the Magnetometer (MAG) and the analysis of MAG observations from MESSENGER's first two flybys of Mercury. “He brought with him a wealth of experience that was truly irreplaceable,” says Brian Anderson, MESSENGER’s Deputy Project Scientist. “He was a fountain of knowledge about anything concerning magnetic fields and magnetometer instrumentation. His breadth of understanding was astonishing. From arcane properties of materials to the intricacies of the electronics design in his instruments, you could count on Mario to have gems of wisdom to offer. To work with Mario on any project was to learn from him. We did our best to be good students, but it will be difficult knowing that we can no longer pick up the phone when we feel the need of his advice.”

Born in Córdoba, Argentina, in 1940, Acuña also brought with him a certain “Argentinean spice,” Anderson says. “Whether it was a novel scientific interpretation that he was determined to get you to take seriously or an engineering detail for calibrating or operating the magnetometer, you always knew where Mario stood, and he was anything but bashful about making his point. Debate was something he loved - the hotter the better! But you could always catch a twinkle in his eye and knew that his heart was with you, and if he was passionate it was because he felt strongly about science and exploration.”

MESSENGER Project Scientist Ralph McNutt knew Acuña since the 1970s, having worked with him on the Voyager 1 mission. “Here you had this brilliant research scientist, but he never had ‘airs’ about him; no pretentions,” McNutt says.

Richard Starr, instrument scientist for the MESSENGERX-Ray Spectrometer, worked with Acuña on several projects, “but the one that stands out the most for me is our collaboration on the X-Ray Spectrometer for the Clark mission.”

Originally scheduled for launch in mid-1996, the Clark spacecraft was to scan Earth with a sophisticated high-resolution camera to provide environmental data. “The Clark mission never launched,” Starr says. “It was canceled by NASA due to cost overruns. But for me personally it was still a great success because of what I learned and accomplished working with Mario. We delivered our instrument on time and on budget.”

Starr also points out that Acuña bridged the gap between scientist and engineer. “For him there really was no difference; it was all part of the same job,” he said. “At Goddard we have the John C. Lindsay Memorial Award for Space Science and the Moe I. Schneebaum Memorial Award for Engineering. As far as I know, Mario is the only person to have won both.”

MESSENGER will enter Mercury’s orbit in less than two years, on March 18, 2011. “While the journey will continue, it won’t be nearly as enjoyable without Mario,” Anderson says. “Perhaps his memory is best served by recalling his devotion to inquiry and advancing human understanding and making sure that the science we do with the MESSENGER magnetometer is up to the Mario Acuña standard.”

For more details, including a blog posted by his family that chronicles the struggle with his illness, visit: http://supermarioAcuña.wordpress.com/.



MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.


 

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NASA will host a media teleconference on Thursday, April 30, at 2 p.m. EDT.


Dwayne Brown
Headquarters, Washington
202-358-1726
[email protected]
Paulette Campbell
Johns Hopkins University Applied Physics Laboratory, Laurel, Md. 240-228-6792 [email protected]
MEDIA ADVISORY: M09-069
NASA TO HOLD BRIEFING TO DISCUSS NEW FINDINGS ABOUT PLANET MERCURY
WASHINGTON -- NASA will host a media teleconference on Thursday, April 30, at 2 p.m. EDT to discuss new data and findings revealed by the Mercury Surface, Space Environment, Geochemistry, and Ranging spacecraft known as MESSENGER.
The spacecraft is the first mission designed to orbit the planet closest to the sun. The probe flew past Mercury on Jan. 14, 2008, and Oct. 6, 2008, conducting the first up-close measurements of the planet since Mariner 10's final flyby on March 16, 1975.
The briefing participants are:
- Marilyn Lindstrom, program scientist, NASA Headquarters in Washington, D.C.
- William McClintock, co-investigator, University of Colorado, Laboratory for Atmospheric and Space Physics in Boulder, Colo.
- James Slavin, co-investigator and chief, Laboratory for Solar and Space Physics, NASA's Goddard Space Flight Center in Greenbelt, Md.
- Thomas Watters, participating scientist, Smithsonian Institution in Washington, D.C.
- Brett Denevi, imaging team member and postdoctoral researcher, Arizona State University in Phoenix
Reporters who would like to participate in the call should submit requests for dial-in instructions to Sonja Alexander at [email protected]. A replay of the teleconference will be available until May 7 by dialing 800-846-6758.
Supporting visuals will be available online April 30 at the start of the teleconference at:
http://messenger.jhuapl.edu/news_room/presscon043009.html
Audio of the teleconference will be streamed live at:
http://www.nasa.gov/newsaudio
-end-
N.

---------- Post added at 08:19 ---------- Previous post was Yesterday at 08:48 ----------

April 30, 2009

Media Contact:
Paulette Campbell
240-228-6792
[email protected]
MESSENGER Reveals Mercury as a Dynamic Planet
Analyses of data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft’s second flyby of Mercury in October 2008 show that the planet’s atmosphere, magnetosphere, and geological past are all characterized by much greater levels of activity than scientists first suspected.

On October 6, 2008, the probe flew by Mercury for the second time, capturing more than 1,200 high-resolution and color images of the planet unveiling another 30 percent of Mercury’s surface that had never before been seen by spacecraft and gathering essential data for planning the remainder of the mission.

“MESSENGER’s second Mercury flyby provided a number of new findings,” says MESSENGER Principal Investigator Sean Solomon at the Carnegie Institution of Washington. “One of the biggest surprises was how strongly the planet’s magnetospheric dynamics changed from what we saw during the first Mercury flyby in January 2008. Another was the discovery of a large and unusually well preserved impact basin that was the focus for concentrated volcanic and deformational activity. The first detection of magnesium in Mercury’s exosphere and neutral tail provides confirmation that magnesium is an important constituent of Mercury’s surface materials. And our nearly global imaging coverage of the surface after this flyby has given us fresh insight into how the planet's crust was formed.”

These findings are reported in four papers published in the May 1 issue of Science magazine.

An Abundance of Magnesium

The probe’s Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, detected significant amounts of magnesium in the planet’s atmosphere, reports William McClintock of the University of Colorado at Boulder’s Laboratory for Atmospheric and Space Physics. “Detecting magnesium was not too surprising, but seeing it in the amounts and distribution we recorded was unexpected,” said McClintock, a MESSENGER co-investigator and lead author of one of the four papers. “This is an example of the kind of individual discoveries that the MESSENGER team will piece together to give us a new picture of how the planet formed and evolved.”

The instrument also measured other exospheric constituents during the October 6 flyby, including calcium and sodium, and he suspects that additional metallic elements from the surface including aluminum, iron, and silicon also contribute to the exosphere.

Radically Different Magnetosphere

MESSENGER observed a radically different magnetosphere at Mercury during its second flyby, compared with its earlier January 14 encounter, writes MESSENGER co-investigator James Slavin, of the NASA Goddard Space Flight Center, lead author of another paper. “During the first flyby, MESSENGER entered through the dusk side of the magnetic tail, measuring relatively calm dipole-like magnetic fields closer to the planet, and then exited the magnetosphere near dawn,” Slavin says. “Important discoveries were made, but scientists didn’t detect any dynamic features, other than some Kelvin-Helmholtz waves along its outer boundary, the magnetopause.”

But the second flyby was a totally different situation, he says. “ MESSENGER measured large magnetic flux leakage through the dayside magnetopause, about a factor of 10 greater than even what is observed at the Earth during its most active intervals. The high rate of solar wind energy input was evident in the great amplitude of the plasma waves and the large magnetic structures measured by the Magnetometer throughout the encounter.”

The magnetospheric variability observed thus far by MESSENGER supports the hypothesis that the great day-to-day changes in Mercury’s atmosphere may be due to changes in the shielding provided by the magnetosphere.

The Rembrandt Basin

One of the most exciting results of MESSENGER’s second flyby of Mercury is the discovery of a previously unknown large impact basin. The Rembrandt basin is more than 700 kilometers (430 miles) in diameter and if formed on the east coast of the United States would span the distance between Washington, D.C., and Boston.

The Rembrandt basin formed about 3.9 billion years ago, near the end of the period of heavy bombardment of the inner Solar System, suggests MESSENGER Participating Scientist Thomas Watters, lead author of another of the papers. Although ancient, the Rembrandt basin is younger than most other known impact basins on Mercury.

“This is the first time we’ve seen terrain exposed on the floor of an impact basin on Mercury that is preserved from when it formed” says Watters. “Landforms such as those revealed on the floor of Rembrandt are usually completely buried by volcanic flows.”

Mercury’s Crustal Evolution

Just over a year ago, half of Mercury was unknown. Globes of the planet were blank on one side. With image data from MESSENGER, scientists have now seen 90 percent of the planet’s surface at high resolution and can start to assess what this global picture is telling us about the history of the planet's crustal evolution, says Brett Denevi, a MESSENGER team member at Arizona State University and lead author of one of the papers.

“After mapping the surface, we see that approximately 40 percent is covered by smooth plains,” she says. “Many of these smooth plains are interpreted to be of volcanic origin, and they are globally distributed (in contrast with the Moon, which has a nearside/farside asymmetry in the abundance of volcanic plains). But we haven’t yet seen evidence for a feldspar-rich crust, which makes up the majority of the lunar highlands and is thought to have formed by flotation during the cooling of an early lunar magma ocean. Instead, much of Mercury's crust may have formed through repeated volcanic eruptions in a manner more similar to the crust of Mars than to that of the Moon.”

Scientists continue to examine data from the first two flybys and are preparing to gather even more information from a third flyby of the planet on September 29, 2009.

“The third Mercury flyby is our final ‘dress rehearsal’ for the main performance of our mission: insertion of our probe into orbit around Mercury in March 2011 and the continuous collection of information about the planet and its environment for one year,” adds Solomon. “The orbital phase of our mission will be like staging two flybys per day. We’ll be drinking from a fire hose of new data, but at least we’ll never be thirsty. Mercury has been coy in revealing its secrets slowly so far, but in less than two years the innermost planet will become a close friend.”


MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

 

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MESSENGER Mission News
May 5, 2009
http://messenger.jhuapl.edu



MESSENGER Co-Investigator Peale Elected to National Academy of Sciences

MESSENGER Co-Investigator Stanton J. Peale, a professor emeritus renowned for his work in planetary science and astrophysics at University of California, Santa Barbara, was among the 72 new members elected to the National Academy of Sciences. The election was held April 28 during the business session of the 146th annual meeting of the Academy. Those elected bring the total number of active members to 2,150, now including four members of the MESSENGER Science Team.

Peale is a leading expert on planetary dynamics. He developed the technique by which MESSENGER will measure the size and state of Mercury's core, and he will lead the interpretation of Mercury Laser Altimeter (MLA) measurements of Mercury's rotation and physical libration.


His theory for Mercury’s forced libration, equivalent to small variations in Mercury's spin rate, was recently utilized to interpret Earth-based radar measurements of Mercury’s motions. Those observations can be explained only if Mercury's core is at least partially molten, a finding that has helped scientists better understand Mercury’s thermal history and the generation of the planet’s intrinsic magnetic field.

As a member of the Academy, Peale will help advise the federal government on science and technology issues. Additional information about the Academy and its members is available online at http://www.nasonline.org.



Mercury Flyby 2, Planned and Actual Images

The April 2009 release to the Planetary Data System of MESSENGER data acquired during the second Mercury flyby offered anew an opportunity to view returned Mercury images adjacent to the simulated version of the same images planned before the flyby. A new version of the Flyby Visualization Tool, called "Mercury Flyby 2, Planned and Actual Images," is available from http://messenger.jhuapl.edu/the_mission/gallery.html and http://messenger.jhuapl.edu/the_mission/visualization.html.

Comparing the planned and acquired images reveals: (1) new details of surface features, (2) different illumination conditions (extent of visible shadows), and (3) the precision of pre-flyby image sequence plans (including camera pointing and prediction of spacecraft location). To simplify use of this tool, no color images are displayed. Each version of the tool utilizes images taken only through one filter out of the full set of 11 filters used for color images with the wide-angle camera.

This version of the Flyby Visualization Tool displays images at 1/4-scale (256-by-256 pixels). The time period highlighted for image sequences shown with this tool, from about 1.5 hours before to 2 hours after closest approach, does not include pre-flyby navigation images and post-flyby "departure movie" images acquired when the spacecraft was far from Mercury.




MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.



 

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MESSENGER Mission News
June 26, 2009
http://messenger.jhuapl.edu



Three New Co-Investigators Added to MESSENGER Team

Brian Anderson, Louise Prockter, and Thomas Zurbuchen have been appointed MESSENGER Co-Investigators by NASA Science Mission Directorate Associate Administrator Edward Weiler.

“Each of these individuals has served admirably as MESSENGER Instrument Scientists, and each has led an important aspect of the analysis and interpretation of MESSENGER observations from the first two Mercury flybys,” notes MESSENGER Principal Investigator Sean Solomon.

As a MESSENGER Deputy Project Scientist, Anderson, of the Johns Hopkins University Applied Physics Laboratory (APL), oversees the orbital operations planning to ensure that observations from all of the instruments are coordinated to meet the mission objectives. He formerly served as the Magnotometer Instrument Scientist. In his additional role as Co-Investigator, Anderson will provide scientific direction to the operation of the Magnetometer instrument in orbit, including in-flight calibration, data validation, science product generation, and coordination with the operation of and data returned from other instruments closely related to investigation of Mercury's magnetic field. In addition, he will lead aspects of the science analysis of data from the Magnetometer and other instruments in understanding Mercury's internal magnetic field and magnetosphere, particularly efforts to identify and quantify the magnetospheric contributions to the observations so as to recover the structure of Mercury's internal magnetic field to the highest fidelity possible.

Prockter, also of APL, serves as the Instrument Scientist for the Mercury Dual Imaging System (MDIS). In her new role as Co-Investigator, she will provide scientific direction to the operation of MDIS in Mercury orbit, including instrument calibration, data validation, science product generation, and coordination with the operation of and data returned from other instruments related to observations of Mercury's surface. In addition, she will lead aspects of the science analysis of MDIS observations to improve our understanding of the geological evolution of Mercury, particularly the study of impact melting during the formation of large craters and basins on Mercury and the contribution of impact melts to smooth plains deposits.

Zurbuchen, of the University of Michigan, is the Instrument Scientist for the Energetic Particle and Plasma Spectrometer. As a Co-Investigator, he will provide scientific direction to the operation of the Fast Imaging Plasma Spectrometer (FIPS) sensor in orbit, including calibration, data validation, science product generation, and coordination with the operation of and data returned from other instruments sensitive to the exosphere and magnetosphere. He will also lead aspects of the science analysis of data from FIPS and other instruments in understanding Mercury's charged particle environment, particularly the analysis of the distribution of plasma ions in Mercury's vicinity and the implications of their energies and compositions for magnetosphere-solar wind interaction at Mercury.

“MESSENGER is one of the most important things I am working on and has accompanied me and my team for over 10 years,” Zurbuchen says. “We look forward to the next 10 years of science data and breakthroughs that will come from MESSENGER, and particularly from the Fast Imaging Plasma Spectrometer.”



MESSENGER Engineer Helps Manage Probe’s Data

Like many young boys of his generation, MESSENGER Team Member Ray Espiritu grew up wanting to fly through space and to design video games. A lack of perfect vision and color blindness prevented him from becoming an astronaut. So, armed with a B.S. in mechanical engineering and a master’s in astronautical engineering, he set to make his mark as a satellite missions operations engineer. To read about how Espiritu and his colleagues at Applied Coherent Technology (ACT), Inc., help preserve the science that fulfills objectives of the MESSENGER mission, click here.



MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
 

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MESSENGER Mission News
August 3, 2009
http://messenger.jhuapl.edu



MESSENGER Mission Passes Five-Year Mark

It’s been five years since MESSENGER was launched atop a Delta II rocket on August 3, 2004, and they have been busy years. It has been a long journey, says MESSENGER Mission Operations Manager Andy Calloway, “not just in distance travelled – just over 3.5 billion miles so far – but also in terms of significant milestones and accomplishments.”

MESSENGER has executed five planetary flybys – one of Earth on August 2, 2005; two of Venus, on October 24, 2006, and June 5, 2007; and two of Mercury, on January 14, 2008, and October 6, 2008. “These were not merely gravity assists, but also major science data collection endeavors that required months of detailed planning,” says Calloway of the Johns Hopkins University Applied Physics Laboratory (APL).

The probe has completed four major deep-space maneuvers (DSMs) and 12 trajectory-correction maneuvers, and mission controllers have been able to forgo six additional planned course corrections by using MESSENGER’s solar panels creatively, harnessing solar radiation pressure to adjust the spacecraft’s trajectory.

Because of the implementation of solar sailing, the MESSENGER team has not used propellant to correct the cruise trajectory of the spacecraft since December 19, 2007, in advance of the first Mercury flyby,” says MESSENGER Mission Systems Engineer Eric Finnegan, of APL. He credits a solar sailing team of engineers – Ken Williams in navigation, Jim McAdams in trajectory design, and Dan O’Shaughnessy in guidance and control – “for increasing mission performance while lowering mission risk by making this technique operational.”

Over the years, MESSENGER’s circuitous journey has presented opportunities within challenges. “We’ve been through periodic extended communication outages as the spacecraft travels on the far side of the Sun from Earth during superior solar conjunctions and frequent close passages by the Sun during perihelion crossings,” Calloway says. “But MESSENGER has traveled as close to the Sun as only three tenths of the Earth-Sun distance during these crossings, providing valuable information and experience in preparation for orbital operations, which begin following the critical Mercury orbit insertion maneuver in 2011.”

In addition to nine major instrument software loads during these five years (with two more planned this month), the third main processor flight software update of the mission was successfully completed on July 14, 2009.

“This new software significantly increases the spacecraft's capabilities for the upcoming orbital phase,” Calloway says. “These processor loads require months of testing, and then once the software is loaded to the spacecraft, the processor has to be rebooted for it to take effect. This rebooting results in a transition to a Sun-safe rotisserie mode in which the spacecraft transmits a beacon signal as it rotates slowly every 3.5 hours. Operators in the control center monitored the signal as it briefly swept through the ground station's field of view one rotation after the reboot, and seven hours later they sent a command with precise timing to halt the rotation and begin restoring the spacecraft to its nominal operational mode.”

More than 90% of Mercury’s surface has now been imaged after MESSENGER's flybys, including territory never seen before by spacecraft, and planning is in full swing for the orbital phase of the mission. Up next is a third pass by Mercury on September 29, 2009, a fifth DSM on November 24, 2009, and then on March 18, 2011, MESSENGER will become the first spacecraft to enter into orbit around the innermost planet.

“When MESSENGER launched five years ago, even our first encounter with Mercury seemed far off,” recounts MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. “Our first two Mercury flybys last year produced an explosion of new and exciting observations, and our cruise through the inner Solar System as of this important anniversary is more than 75% complete. The entire MESSENGER team is eagerly awaiting the first observations of Mercury from orbit.”



MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
 
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