A NASA spacecraft is currently on it's way to Mercury. MErcury Surface Space ENvironment GEochemistry and Ranging spacecraft (MESSENGER for short) was launched from Cape Canaveral Air Force Station on 3rd August 2004.

MESSENGER made a gravity assist flyby of the Earth on 21st July 2005. MESSENGER will make two flybys of Venus in October 2006 and June 2007. It will then make 3 flybys of Mercury in January 2008, October 2008 and September 2009. These flybys will correct it's orbit around the sun so that the spacecraft can slip into Mercury orbit in March 2011. It will then map virtually all of Mercrys surface.

The Europe Space Agency (ESA) and the Japanese Space Exploration Agency (JAXA) have plans for a mission called BepiColombo. To be launched in 2013 BepiColombo will place two satellites in obit around Mercury 6 years later.

Only one other spacecraft has visited Mercury, Mariner 10 was launched in 1973 and made three flybys of the planet on 29th March and 21st September 1974, and 16th March 1975.



MESSENGER Mission News
June 21, 2006

MESSENGER Flips Sunshade Toward the Sun

The MESSENGER spacecraft performed its final "flip" maneuver for the mission on June 21. Responding to commands sent from the MESSENGER Mission Operations Center at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., through NASA's Deep Space Network antenna station near Goldstone, Calif., the spacecraft rotated 180°, pointing its sunshade toward the Sun.

The 16-minute maneuver, designed to keep MESSENGER operating at safe temperatures as it moves closer to the Sun, wrapped up at 9:34 a.m. EDT, with successful reacquisition of signal from MESSENGER’s front-side antenna. The spacecraft was 196.5 million kilometers (122.1 million miles) from Earth and 144.6 million kilometers (89.8 million miles) from the Sun when the maneuver occurred.

MESSENGER had been flying with its back to the Sun since a March 8 “flop,� allowing it to maintain temperatures within safe operating ranges at Sun distances greater than 0.95 astronomical units (1 AU is Earth’s distance from the Sun). Mission plans call for the spacecraft to keep its sunshade facing the Sun for the remainder of its cruise and science orbital operations around Mercury.

"Initial indications look very good� says MESSENGER Mission Operations Manager Mark Holdridge, of APL. "Spacecraft temperatures are coming down as expected and all systems and instruments are nominal."�

The team will now turn its attention to preparing for the first Venus flyby on October 24. "We have mission simulations and flight tests coming up to test particular operations that will have to occur during the Venus flyby,"� Holdridge says. "There will be a 57-minute solar eclipse during the October operation, so we will so be testing the flight systems in the flyby configuration to verify they will behave properly during the eclipse period."�

On August 11, for instance, the team will conduct a flight test of the new autonomy that will power off components prior to the solar eclipse, allow the battery to discharge by approximately the same amount as during the real eclipse, and then power on components again once the battery is recharged, all in a more controlled setting with real-time visibility. This test will be combined with a battery reconditioning.

Later in August and through September, during the approach to Venus, MESSENGER’s navigation team will use the Mercury Dual Imaging System cameras onboard the spacecraft to take a series of optical navigation pictures. These images are not required for the Venus flyby but will be used by the MESSENGER navigation team for calibration and as practice for the optical navigation imaging to be utilized at Mercury.

Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
August 3 , 2006

Happy Anniversary, MESSENGER!

Today marks the second anniversary of MESSENGER’s launch. “It’s still more than four and a half years to Mercury Orbit Insertion in March 2011, and there are many milestones between now and then,” says Dr. Sean C. Solomon, of the Carnegie Institution of Washington, who leads the mission as principal investigator. “But it’s worth pausing for a few moments today to appreciate how far we’ve come.”

And just how far has the spacecraft traveled since its Aug. 3, 2004, launch from Cape Canaveral Air Force Station, Fla.? Nearly 1.2 billion miles. MESSENGER’s computers have executed 180,271 commands since liftoff, a time interval that includes seven major trajectory correction maneuvers.

“It’s been a busy two years,” says MESSENGER Mission Operations Manager Mark Holdridge, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. “We’ve been by Earth and now we are headed for Venus, another major milestone in this mission.”

MESSENGER team members have been running tests all summer to make sure the spacecraft will operate as intended during the Venus flyby – the first of two swings past the clouded planet –scheduled for Oct. 24, 2006. There will be a 57-minute solar eclipse during that operation. So on Aug. 11, engineers will turn the spacecraft solar panels edge-on to the Sun and discharge the battery, much in the same manner that the power system will function during the Venus flyby, to verify that the system will respond appropriately.

Two weeks later, on Aug. 21, engineers will conduct a “star-poor” region test, pointing the spacecraft’s star tracker in a region of the sky that might be utilized during the Venus operations. Holdridge says a similar test was conducted on July 26, “and we got a positive result from that test; the preliminary results look good.”

All in all, Holdridge says, all systems are functioning very well. “The spacecraft is very healthy, and the team is working hard to make this first flyby of Venus a success!”

For encounter details and graphics associated with the October maneuver, go online to http://messenger.jhuapl.edu/the_mission/MESSENGERTimeline/VenusFlyby1.html.

MESSENGER Engineer Named AIAA Engineer of the Year

APL’s T. Adrian Hill, the fault protection and autonomy lead for MESSENGER, was recently named Engineer of the Year by the Baltimore chapter of the American Institute of Aeronautics and Astronautics (AIAA). Each year, local AIAA chapters present this award to a member who has made significant contributions to the field of engineering. For more information, go online to http://www.jhuapl.edu/newscenter/pressreleases/2006/060623b.asp.

Where is Mercury?

Mercury's orbit is so close to the Sun that we can only see it from Earth either just before sunrise or just after sunset. For a diagram of the orbits of the inner planets, as they appear today, go online to http://btc.montana.edu/messenger/wheremerc/wheresmerc.php


Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
September 15, 2006

MESSENGER Tweaks Its Route to Mercury

The MESSENGER trajectory correction maneuver 11 (TCM 11) on September 12 lasted just under four minutes and adjusted the spacecraft’s velocity by about 1.68 meters per second (5.5 feet per second). The short-duration maneuver kept MESSENGER on track for next month’s Venus flyby.

Tuesday’s maneuver started at 7 p.m. EDT; mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 12 minutes later, when the first signals indicating thruster activity reached NASA's Deep Space Network tracking station outside Canberra, Australia.

While MESSENGER has used all 17 of its thrusters in completing several successful maneuvers, TCM 11 was the first course correction to require two sets of primary thrusters. Part A of the maneuver began at 7 p.m. EDT and lasted 23 seconds; Part B began at 7:10 p.m. and lasted 202 seconds.

Operators moved MESSENGER in two perpendicular movements during the maneuver – instead of on a straight path – to protect the spacecraft’s heat-sensitive electronics from direct sunlight. The movements kept the sunshade in position to block the blinding sunlight, which warms the spacecraft nearly three times faster now than if MESSENGER were orbiting Earth.

The next TCM – the last chance for mission controllers to tweak the spacecraft’s route prior to the Venus flyby – will take place no later than October 12. For graphics of MESSENGER's orientation during the maneuver, visit the "Trajectory Correction Maneuvers" section of the mission Web site at http://messenger.jhuapl.edu/the_mission/mission_design.html.

MESSENGER Team to Share Notes with Venus Express

The primary goal of MESSENGER’s October flyby of Venus is to receive a gravity assist that will put it on course to its final destination: Mercury. None of its instruments will be powered on near the time of closest approach, because Venus will be on the opposite site of the Sun from the Earth and the spacecraft will be out of direct communication for approximately three weeks.

MESSENGER will fly by Venus a second time, on June 6, 2007, and during that event all payload instruments will be trained on the planet before, during, and after closest approach. The MESSENGER team is working closely with the team operating Europe’s Venus Express mission to take advantage of the fact that two spacecraft will be in the vicinity of Venus at the same time.

The European Space Agency (ESA) launched the Venus Express mission in November 2005; the spacecraft entered Venus orbit in April and in June began its primary science mission to unveil the source of the planet’s dense, turbulent and toxic atmosphere. Venus Express carries seven primary instruments, many of which were spares left over from previous ESA missions, such as the agency's Mars Express and comet-bound Rosetta programs.

For the October flyby, MESSENGER mission managers will exchange trajectory information with the Venus Express team. For the second flyby in June 2007, a range of coordinated observations of Venus is now being planned.

“As it is with any mission to the other planets in the solar system, when you have the opportunity to make multiple observations from different spacecraft at the same time you are giving yourself the opportunity to learn more than you would learn from either one operation on its own,” says Ralph McNutt, MESSENGER’s project scientist, from the Applied Physics Laboratory.

For information about Venus Express, go online to http://sci.esa.int/science-e/www/area/index.cfm?fareaid=64.

MESSENGER Added to Solar System Simulator Web Site

This summer the MESSENGER spacecraft was added to NASA Jet Propulsion Laboratory’s (JPL) Solar System Simulator Web site. This highly capable, award-winning site features numerous options for viewing the planets, 24 selected planetary satellites, and the solar system using a variety of fields of view. The orbits of eleven interplanetary spacecraft are also featured.

JPL uses the Solar System Simulator as the sole tool for its "Where is Cassini?" feature (see http://saturn.jpl.nasa.gov/operations/present-position.cfm). The Solar System Simulator features the full-mission reference trajectory (reconstructed orbit as well as predicted orbit through the nominal end of mission) for the MESSENGER spacecraft.

The see the MESSENGER feature, go online to http://space.jpl.nasa.gov, and highlight “MESSENGER spacecraft,” within the “Show me” prompt.

Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
October 24, 2006

MESSENGER Completes Venus Flyby

NASA’s Mercury-bound MESSENGER spacecraft came within 2,990 kilometers (1,860 miles) of the surface of Venus early this morning during its second planetary encounter. The spacecraft used the tug of the planet's gravity to change its trajectory significantly, shrinking the radius of its orbit around the Sun and bringing it closer to Mercury.

MESSENGER swung by Venus at 8:34 UTC (4:34 a.m. EDT), according to mission operators at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. About 18 minutes after the approach, an anticipated solar eclipse cut off communication between Earth and the spacecraft. Contact was reestablished at 14:15 UTC (10:15 a.m. EDT) through NASA's Deep Space Network, and the team is collecting data to assess MESSENGER’s performance during the flyby.

Shortly before the Venus flyby the spacecraft entered superior conjunction, placing it on the exact opposite side of the sun as Earth, making communication between MESSENGER and Mission Operations difficult, if not impossible. “So we are not making any scientific observations at the time of this flyby,” says Sean C. Solomon, the mission's principal investigator, from the Carnegie Institution of Washington. “We shall conduct a full suite of observations surrounding the second flyby in June 2007.”

In late November, when routine radio contact with the spacecraft is re-established, the team will collect data to determine how closely MESSENGER followed its plans and to update knowledge of its orbit. This information will enable operators to plan for the December 12 trajectory correction maneuver that will target the spacecraft for the second Venus flyby.

The spacecraft is relying on multiple planetary flybys to “catch” Mercury and begin orbiting the planet. Another flyby of Venus in June of 2007 will further alter the spacecraft’s orbit so that it will fly by Mercury in January of 2008. Three close approaches to Mercury will be required to bring the velocity of MESSENGER close enough to the orbital velocity of Mercury such that its main engine can brake the spacecraft into Mercury orbit in March of 2011.

Earlier this month, the MESSENGER Dual Imaging System (MDIS) snapped pictures of Venus from a distance of about 16.5 million kilometers (10.3 million miles). Those images are available online at http://messenger.jhuapl.edu/the_mission/pictures/pictures.html. Despite the low resolution of the images, it’s possible to see that Venus is shrouded in a thick blanket of clouds that hides its surface. Also available online are updated animations, one showing Venus from the spacecraft from 90 minutes before to 90 minutes after the flyby, including the time of the eclipse. Those images are online at http://messenger.jhuapl.edu/the_mission/movies.html.

MESSENGER will conduct the first orbital study of Mercury, the least explored of the terrestrial ("rocky") planets that also include Venus, Earth and Mars. Over one Earth year— or four Mercury years — MESSENGER will provide the first images of the entire planet and collect detailed information on the composition and structure of Mercury's crust, its geologic history, the nature of its atmosphere and magnetosphere, and the makeup of its core and polar materials.

MESSENGER, short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging, is the seventh mission in NASA's Discovery Program of lower cost, scientifically focused exploration projects. APL designed, built and operates the MESSENGER spacecraft and manages the mission for NASA's Science Mission Directorate.

For more information, visit the MESSENGER Web site at http://messenger.jhuapl.edu.

Source: JHUAPL - MESSENGER - Status Report

Approaching Venus

On Oct. 24, 2006, the MESSENGER spacecraft came within 2,990 kilometers (1,860 miles) of Venus during its second planetary encounter. Twenty days before closest approach to Venus the MESSENGER Dual Imaging System snapped pictures of the planet from a distance of about 16.5 million kilometers (10.3 million miles). Despite the low resolution of the image on the left, one can see that Venus is shrouded in a thick blanket of clouds that hides its surface. The picture on the right is the same image expanded four times, clearly showing the dense Venusian cloud cover.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington


Source: JHUAPL - MESSENGER - Photos

MESSENGER Mission News
November 6, 2006

Upcoming Mercury/Sun Transit Whets the Appetite for MESSENGER Discoveries

On Wednesday, November 8, the planet Mercury will make a rare trek across the face of the Sun, beginning at 2:12 p.m. EST and lasting for nearly five hours. Observers in North and South America, Australia, and parts of Asia will have a good view; the transit also will be captured via a live Webcast that will include discussions on the science, technology, and history of the transit, as well as current knowledge of the Sun and space weather.

Mercury transits don't happen very often. The last was on May 7, 2003, and the next doesn't come until May 9, 2016. The event underscores the importance of the NASA’s Mercury-bound MESSENGER spacecraft, which will conduct the first orbital study of Mercury, the least explored of the terrestrial ("rocky") planets that also include Venus, Earth, and Mars.

“There is still so much that we don’t know about Mercury,” says Deborah Domingue, MESSENGER’s deputy project scientist and a planetary astronomer at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. The mission will attempt to answer several questions about the innermost planet, such as: Why is Mercury – the densest planet in the solar system – mostly made of iron? Why is it the only inner planet besides Earth with a global magnetic field? How can the planet closest to the Sun, with daytime temperatures as high as 840° degrees Fahrenheit, have what appears to be ice in its polar craters?

“The last time we set our sights on Mercury was 30 years ago,” Domingue notes, referring to NASA’s Mariner 10 spacecraft, which sailed past the planet three times in 1974 and 1975 and gathered detailed data on less than half the surface. MESSENGER, carrying seven scientific instruments on its compact and durable composite frame, will provide the first images of the entire planet. The mission will also collect detailed information on the composition and structure of Mercury's crust, its geologic history, the nature of its thin atmosphere and active magnetosphere, and the makeup of its core and polar materials.

Domingue will talk about MESSENGER (short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging) during the transit Webcast, which is geared toward middle school students. “I’m going to talk about MESSENGER’s science goals, the Mariner missions, and why it’s so difficult to send a spacecraft into the inner solar system,” she says. “So while this is geared to students, the general public should tune in if only to be reminded that NASA is still actively involved in exploration, and not just the outer planets. We are still boldly going where no one has gone before!”

The hour-long “Transit of Mercury Webcast,” hosted by the NASA Digital Learning Network, will begin at 1:30 p.m. EST. In addition to APL’s Domingue, the event will feature:

• panel discussions with scientists from NASA’s Goddard Space Flight Center, educators and an amateur astronomer from NASA Langley Research Center;
• two NASA “Explorer” schools, connected for a live questions-and-answer session;
• a telescope “'safety viewing”' demonstration with instructions on how to view the transit using a classroom solarscope;
• live images of the transit from two NASA satellites, SOHO and TRACE; and
• live ground-based images from the Kitt Peak National Observatory in Arizona and the University of Hawaii’s Mauna Kea telescopes.

To view the Web cast, go online to http://sunearthday.nasa.gov/2007/events/mercurytransit.php.

MESSENGER Team Member Highlight: Stan Peale

Stan Peale, professor emeritus and research professor of physics at the University of California, Santa Barbara, developed the technique by which MESSENGER will measure the state of Mercury's core. He is well-known for his contributions to the dynamics of solar-system bodies and has been published in scores of scientific journals. But if you want to find out about his very early work with truck gardens, read his profile online at http://messenger.jhuapl.edu/who_we_are/member_focus.html.

Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
November 10, 2006

A MESSENGER SCIENCE TEAM MEMBER GETS A PREVIEW OF DISCOVERIES TO COME
(A report on Mercury transiting the Sun, by Clark R. Chapman, of the Southwest Research Institute, Boulder, Colo.)

Mercury is a very difficult planet to see in the twilight or dawn skies, because it stays so close to the Sun. This innermost planet, and the smallest one (if you accept the recent demotion of Pluto), is occasionally easy to see, by special means, when it passes directly between the Earth and the Sun. These events, called "transits of Mercury," occur about a dozen times a century. They are visible from somewhere on the Earth, but require a small telescope, equipped with special filters, so that the observer isn't blinded by the Sun. They can also be viewed by projecting an image of the Sun onto a white card.

I had the good fortune to be in Tucson, Ariz., on November 8, when the most recent transit occurred with the Sun high in the cloudless Arizona skies. This was the best Mercury transit opportunity in North America since I saw my first transit of Mercury in 1960. My wife and I visited famed comet discoverer David Levy at his home in the desert near Tucson. Also attending were Eli Maor, author of the book "Venus in Transit," which is about the even rarer transits of Venus (these occur only twice a century; the last one was in 2004, the next one in 2012, and then not again until the 22nd century). Maor and his had wife traveled from Chicago to be assured of sunny skies. Several other amateur astronomers also converged on Levy's "telescope farm" for the event.

Levy is one of the co-discoverers of Comet Shoemaker-Levy 9, which famously split into about 20 fragments — each of which crashed into Jupiter — during a one-week period in 1994. Although he has discovered many comets in earlier years (21 to be exact) professionally operated search programs are claiming most of the comet discoveries these days. But on this day, Levy was still smiling about find number 22, his first comet discovery in a dozen years. Just a few weeks before the Mercury transit, he had found a fuzzy blob next to Saturn in his telescope's field-of-view. He feared it was simply a strange optical reflection of Saturn, but it turned out to be a real comet!

On Wednesday, Mercury started to cross the face of the Sun around mid-day, Tucson time. We arrived mid-afternoon to find the planet already two-thirds of its way across the Sun. Looking through a telescope equipped with a hydrogen-alpha filter, I was startled by the deep red color of the Sun's chromo sphere, mottled by the gas jets called spicules. Then I noticed the solid-black disk of Mercury, perfectly round in shape, silhouetted in front of the Sun. From minute-to-minute, it slowly crawled from spicule to spicule.

Levy's back-yard hospitality extended beyond his dozen fellow astronomers and friends onsite; as a SkyGuide for Slooh.com, he hosted thousands of virtual transit watchers. He was leading a live broadcast featured on AOL, in association with Slooh.com, an online portal for live astronomy that offers its members an opportunity to explore space live in real time, seeing many objects difficult to view with typical backyard telescope equipment through its easy to use web interface.

Levy provided commentaries during the five-hour event while live images of the transit were being net cast on AOL. As Mercury approached the end of its transit, he interviewed me about MESSENGER. I told the audience about MESSENGER's recent pass by Venus, and I described the spacecraft's future path and plans for exploring Mercury.

One of the most beautiful features of the Sun, when viewed through a hydrogen-alpha filter, are the enormous, wispy "prominences" projecting beyond its edge. The looping structures visible on November 8, confined by the Sun's magnetic field, were larger than Earth. As Mercury slowly approached the edge of the Sun, it became apparent that it might pass in front of a particularly large prominence just after leaving the edge of the Sun.

Levy described to Slooh.com listeners the optical illusion called the "black-drop effect," just before the leading side of little Mercury's disk reached the edge of the Sun. And then, suddenly, Mercury became a notch in the solar profile, rather than a complete disk. The notch dwindled in size and, at about 5:10 p.m. MST, the transit was over.

Or was it? Maybe we could watch the planet's disk faintly framed by the prominence. But, unfortunately, the Sun was lowering toward the horizon, and the telescope was now peering through branches of a desert Palo Verde tree, so the viewing was obscured.

A few minutes later, we watched for the "green flash" as the top edge of the Sun finally blinked out behind a distant mountain range, but I saw nothing special as the light began to fade and the air quickly cooled. Later, as the group enjoyed supper at the Levy's home, we talked about the miracles of shadows. In a sense, we had just been in Mercury's shadow, as cast on Earth. But, like the "shadow" of a stratospheric jetliner, Mercury's shadow only infinitesimally dimmed the sunlight on Earth. But by using the proper telescopic equipment, we were rewarded with a good view of the entire circumference of the planet, which will soon to be orbited (in 2011) by the MESSENGER spacecraft.

Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
December 2, 2006

MESSENGER LINES UP FOR ITS SECOND VENUS FLYBY

MESSENGER’s Trajectory Correction Maneuver 13 (TCM-13), its first since its maiden pass at Venus in October, was successfully executed December 2 and will help keep the spacecraft on track for its second flyby of Venus on June 5, 2007. This maneuver changed MESSENGER’s velocity by 25.6 meters per second (84.1 feet per second) in a direction oriented 41.7° from the spacecraft-to-Sun direction.

For the first time, the burn was conducted in three parts – called “components” – to protect sensitive portions of the spacecraft from overheating by direct exposure to sunlight. Three rather than two components were required in order to maintain sufficient fuel reserves in the smallest fuel tank. MESSENGER is now about 81.8 million miles from the Sun, but during all three components of TCM-13 the sunshade protected heat-sensitive parts of the spacecraft from direct sunlight.

Mission controllers at The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., monitored the maneuver, communicating with MESSENGER through NASA's Deep Space Network tracking station outside Goldstone, Calif. The separate components of the maneuver, lasting about 1,670 seconds, 97 seconds, and 1,640 seconds, began at 4 p.m., 5 p.m., and 10 p.m. EST, respectively.

With TCM-13 complete, the team now turns its attention to preparing for scientific observations of Venus during the June 2007 flyby. Over the coming months, the team will have at least three more opportunities to tweak MESSENGER’s route before the Venus encounter.

MERCURY DANCES WITH JUPITER AND MARS IN UNUSUAL PLANETARY TRIO

Between December 7 and 14, Mercury observers will be able to witness the planet in a rare dance with Jupiter and Mars. The event is known as a planetary trio, referring to three planets residing within a circle whose diameter spans less than 5° of sky and fits within the approximate 6° field of view of ordinary binoculars.

Space.com says the best time to look for the trio will be around 6:30 a.m. local standard time, when they will be hovering very low over the east-southeast horizon in the brightening dawn twilight. The trio’s low altitude and proximity to glare of the rising Sun will probably render Mars invisible to the unaided eye; Mercury and Jupiter should be readily visible with only slight difficulty, as they respectively will appear about three and 19 times brighter than Mars.

The trio will be most compact – fitting within just a 1° circle – on December 10. On this morning, the three planets will resemble a compact arrowhead pointing west, with Mars at the tip. There will also be separate conjunctions between Mercury and Mars (December 9), Mercury and Jupiter (December 10), and Mars and Jupiter (December 11).

Also, on the morning of December 10, Mercury will appear to lie very close below and to the right of the second-magnitude star Graffias in Scorpius, the Scorpion.

Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
February 5, 2007

A Day in the Life of Mercury’s Orbit

MESSENGER isn’t due to begin its orbit of Mercury until March 2011, but engineers and scientists at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., are already rehearsing for the year-long observation of the “swiftest planet,” through a series of Day-in-the-Life (or “DitL”) tests.

“The system that we’ll use for orbiting Mercury will be significantly different from what we use for cruise and flybys,” explains APL’s Mark Holdridge, a member of the MESSENGER mission operations team. “These exercises put the flight team and ground systems through their paces during a realistic simulation to provide some practice for readiness, to shake down the systems and procedures, and to try to uncover flaws or areas for improvement.”

The team recently completed the first test, which was based on a relatively benign orbit scenario, Holdridge explains. “This first one wasn’t meant to be a stress test—there were no solar eclipses, no encounters of hot-pole regions, nothing that required special attention. But it allowed us to work out tools and instruments and procedures, and we learned a lot of lessons that we’ve folded into the next exercise.”

The team is now building command sequences for DitL 2, which tackles a dusk-to-dawn orbit in which the spacecraft always faces the Sun while riding above the line that separates day from night. “This scenario, while still not particularly stressful, is very interesting for radio science purposes,” Holdridge says. “There are times during that orbit when the Sun is between Mercury and Earth, and we can’t communicate with the spacecraft when that happens. The radio science team wants to trek through those periods.”

The team will conduct several of these one-day exercises before tackling more complicated week-long scenarios. Fitting these crucial dry runs in a schedule that involves real-time monitoring of the spacecraft and preparations for the second Venus flyby in June is challenging. “It’s like working in three different time zones,” Holdridge says. “But we have to plan far ahead enough to work through any kinks and make sure we are ready to make the most of our stay at Mercury. We have just one year in orbit around the planet, and we want to hit the ground running.”


Preview of Upcoming Venus Flyby

Preview what MESSENGER's second Venus flyby on June 5 will look like with this featured animation of the event. The mission gallery, available online at http://messenger.jhuapl.edu/the_mission/gallery.html, contains a variety of images, photos, animation, and movies about all aspects of the mission—from pre-launch preparations, to images returned from the planetary flybys, to artists' renditions of the MESSENGER spacecraft on its voyage to the inner solar system. Check back often; new materials are added as the mission progresses.

Web Profile: Robin Vaughan

Though Robin Vaughan has nearly 20 years of experience with interplanetary missions, MESSENGER has presented her with a host of new challenges. As the lead engineer for the mission’s guidance and control (attitude control) subsystem, Vaughan coordinated, planned and conducted tests for spacecraft integration through launch, and now continues to monitor the craft’s performance in flight. Meet Robin and learn about her critical role on the MESSENGER team at http://messenger.jhuapl.edu/who_we_are/member_focus.html.


Mercury Makes an Appearance

Mercury is the most difficult of the five bright “naked eye” planets to see from Earth. But for those living in the Northern Hemisphere, a great window of opportunity for viewing the planet is about to open. Mercury will reach greatest eastern elongation from the Sun at 18° on February 7. Elongation is an astronomical term that refers to the angle between the Sun and a planet, as viewed from Earth.

The planet will be visible about 7° degrees below and to the right of Venus in the western evening sky about 40 minutes after sunset. This opportunity remains through at least March 19. Mercury will emerge at sunset two more times this year: on June 2 and September 29. On three other occasions—March 22, July 20, and November 8—the planet will reach greatest western elongation and materialize in the morning sky. For a diagram of the orbits of the inner planets, as they appear today, go online to http://btc.montana.edu/messenger/wheremerc/wheresmerc.php.

Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
February 20, 2007

PRIMING INSTRUMENTS TO MAP MERCURY’S CRUST

Understanding if ice exists on the surface of Mercury, and if so what types, will mark an important component of the investigations by the MESSENGER spacecraft about the origin and evolution of the solar system’s inner planets. This month, instrument engineers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., turned on the Neutron Spectrometer (NS)—one of several sensors aboard MESSENGER that will be key to sorting out the mystery of Mercury’s surface.

The NS will collect data about the composition of the uppermost tens of centimeters of Mercury’s crust by measuring the numbers and energies of neutrons that reach the MESSENGER probe as it passes near the planet. The NS together with a gamma ray sensor make up the Gamma-Ray and Neutron Spectrometer (GRNS) instrument.

The NS will map variations in the fast, thermal, and epithermal neutrons Mercury’s surface emits when struck by cosmic rays. “Fast” neutrons shoot directly into space; others collide with neighboring atoms in the crust before escaping. If a neutron collides with a small atom (like hydrogen), it will lose energy and be detected as a slow (or thermal) neutron. Scientists can look at the ratio of thermal to epithermal (slightly faster) neutrons across Mercury’s surface to estimate the amount of hydrogen—possibly locked up in water molecules—and other elements.

Subtracting the Background Noise

APL’s Edgar Rhodes, an instrument scientist on the MESSENGER mission, says the current NS calibration will “tweak the electronic thresholds and voltages for the detectors to assure that the most interesting parts of the neutron spectra are within the energy ranges of the instrument before the upcoming second Venus flyby on June 5.”

In space, the spacecraft is bombarded continuously from all directions by galactic cosmic rays, high-energy particles (mostly protons) thought to originate from remnants of supernovae in our galaxy, explains APL’s John Goldsten, the GRNS instrument engineer.

“On Earth, we are protected from these penetrating rays by our atmosphere; but in the vacuum of space they collide directly with spacecraft materials, smashing into atomic nuclei, and sending off energetic neutrons,” he says. “These energetic neutrons, in turn, collide with other atoms and produce a host of lower-energy neutrons and gamma rays. These signals pose a serious background in the instrument that needs to be ‘subtracted out’ from the total signal measured near a planet. After all, it’s the composition of the planet and not the spacecraft we are trying to measure.”

To make matters more difficult, Goldsten adds, some components of this induced spacecraft background build up over time, “and so it is important to make periodic measurements to characterize this background to perform a proper analysis and interpretation of the science data.”

Searching for Solar Neutrons

The NS will remain on during most of MESSENGER’s cruise phase and return data from Venus flyby 2 in June, three Mercury flybys in 2008 and 2009, and one Earth year in Mercury orbit starting in 2011.

The NS is a low-power instrument that can safely be powered on indefinitely, Goldsten says. “We plan to take special advantage of the unique measurements the NS can produce as it journeys through the inner solar system; a region of space never before studied with this type of instrument.”

“Looking for the presence of energetic neutrons streaming away from the Sun during solar flares is of particular scientific interest to physicists trying to model and understand the underlying mechanisms of solar activity,” he continues. “Solar neutrons are very difficult to observe from Earth because these sub-atomic particles by themselves—not bound inside an atomic nucleus—are not stable and decay away in about ten minutes, so only the most energetic (fastest moving) neutrons reach Earth before disintegrating, and these are very few. But as the MESSENGER spacecraft journeys closer to the Sun and gets inside the orbit of Venus, the likelihood of observing solar neutrons increases dramatically because we get a chance to capture them before they can decay away.”

Another reason to operate the NS during the long cruise to Mercury is to help the Interplanetary Network of satellites detect and locate Gamma Ray Bursts—the most energetic events known in the Universe—which produce monstrous flashes of gamma rays that appear in the sky at random times and from random locations.

“Detecting these gamma ray bursts simultaneously at distant spacecraft helps to triangulate their direction so that observatories can quickly aim powerful telescopes to study the optical counterpart or ‘afterglow’ of these colossal events, hypothesized to mark the collapse of stars into black holes or the collision of super dense neutron stars,” Goldsten says. “While the NS is optimized to detect neutrons, gamma rays appear as a steady background signal, so any sudden changes in this background signal can be used as a gamma-ray burst monitor. Gamma-ray bursts are typically detected about once a day, and no two are exactly alike; some last milliseconds, while others may continue for minutes.”

From an engineering point of view, the GRNS is a flexible instrument with many controls and settings that can be adjusted remotely via commands to the spacecraft. “This flexibility is important as we cannot easily simulate the galactic cosmic ray environment on the ground,” Goldsten says. “Optimizing the in-flight settings is usually an iterative process where we make small changes and then analyze the results. We then collect long-term data with the final settings to establish the instrument baseline prior to an encounter such as the upcoming Venus flyby.”

More information about the GRNS is available online at
http://btc.montana.edu/messenger/instruments/grns.php

STAT CORNER: Now 931 days after launch, MESSENGER is about 71.9 million miles (115.7 million kilometers) from the Sun and 162.3 million miles (261.2 kilometers) from Earth. At that distance, a signal from Earth reaches the spacecraft in 14 minutes and 31 seconds. The spacecraft is moving around the Sun at 73,111 miles (117,661 kilometers) per hour. MESSENGER's onboard computers have executed 225,580 commands from mission operators since launch on August 3, 2004.


Preview of Upcoming Venus Flyby

Preview what MESSENGER's second Venus flyby on June 5 will look like with this featured animation of the event. The mission gallery, available online at http://messenger.jhuapl.edu/the_mission/gallery.html, contains a variety of images, photos, animation, and movies about all aspects of the mission—from pre-launch preparations, to images returned from the planetary flybys, to artists' renditions of the MESSENGER spacecraft on its voyage to the inner solar system. Check back often; new materials are added as the mission progresses.

Source: JHUAPL - MESSENGER - Status Report

The BepiColombo mission consists of two individual orbiters: the Mercury Planetary
Orbiter (MPO), that will map the planet, and the Mercury Magnetospheric Orbiter
(MMO), that will investigate its magnetosphere.

BepiColombo will help reveal information on the composition and history of Mercury,
and the history and formation of the inner planets in general, including Earth.

Credits: EADS Astrium

26 February 2007
BepiColombo, ESA's mission to explore planet Mercury, has been definitively 'adopted' by the Agency’s Science Programme Committee (SPC) last Friday. The mission will now start its industrial implementation phase, to prepare for launch in August 2013.

BepiColombo is the next European planetary exploration project, and will be implemented in collaboration with Japan. A satellite 'duo' – consisting of an orbiter for planetary investigation and one for magnetospheric studies – will reach Mercury after a six-year journey towards the inner Solar System, to eventually perform the most extensive and detailed study of the planet ever performed so far.

The 'Mercury Planetary Orbiter' (MPO) will be under ESA responsibility, while the Mercury Magnetospheric Orbiter (MMO) will be under the responsibility of the Japan Aerospace Exploration Agency (JAXA). The Mercury Transfer Module (MTM), also under ESA responsibility, will provide the electrical and chemical propulsion required to perform the cruise to Mercury. These three modules assembled together for the launch and cruise phase make up a single composite spacecraft.


This artist’s impression shows ESA’s BepiColombo’s Mercury Planetary Orbiter (MPO) that, together with a second spacecraft, the Japanese Mercury Magnetospheric Orbiter (MMO), makes the BepiColombo mission at Mercury.

The MPO will study the planet itself and, among several investigations, it will make a
complete map of Mercury at different wavelengths. It will also map the planet's
mineralogy and elemental composition and determine whether the interior of the
planet is molten or not.

Credits: ESA - C.Carreau

The MPO will carry a highly sophisticated suite of eleven scientific instruments, ten of which will be provided by Principal Investigators through national funding by ESA Member States and one from Russia.

The MMO will carry five advanced scientific experiments that will also be provided by nationally funded Principal investigators, one European and four from Japan. Significant European contributions are also provided to the Japanese instruments.

After a competitive definition phase started in 2001, ESA is now ready to award Astrium GmbH (Friedrichshafen, Germany) with the prime contract for the BepiColombo implementation phase, consisting of the mission design and of the design, development and integration of the 'cruise-composite' spacecraft. Astrium GmbH will also provide engineering support to the launch campaign and the in-orbit commissioning phase.


This artist’s view shows the two BepiColombo orbiters (MPO and MMO) mounted on
top of their transfer module (cruise configuration).

For its journey to destination BepiColombo will cleverly use the gravity of the Moon,
Earth, Venus and Mercury itself in combination with the thrust provided by solar-electric
propulsion (SEP). During the voyage to Mercury, the two orbiters and transfer module,
consisting of solar-electric propulsion and chemical propulsion units, will form one single composite spacecraft.

Once approaching Mercury, the transfer module will be separated and the composite
spacecraft will use conventional rocket engines and the so-called 'weak stability
boundary capture technique' to bring it into polar orbit around the planet. When the
MMO orbit is reached, the MPO will separate and lower its altitude by means of
chemical propulsion to its operational orbit. Scientific investigations will go on for at
least one Earth year.

Credits: ESA - C.Carreau

Reaching Mercury and placing a spacecraft in a stable orbit around it is a difficult task due to the gravity of the Sun. BepiColombo will reach the planet - visited only by NASA's Mariner 10 in the mid seventies - in a truly novel way.

During the cruise, the mission will make clever use of the gravity of the Moon, Earth, Venus and Mercury itself in combination with the thrust provided by solar-electric propulsion. This innovative combination of low thrust space propulsion and gravity assist has been demonstrated by ESA's technology mission, SMART-1.

When approaching Mercury, the transfer module will be separated and the two-spacecraft composite will use conventional rocket engines and the so-called 'weak stability boundary capture technique' to bring it into polar orbit around the planet. When the MMO orbit is reached, the MPO will separate and lower its altitude by means of chemical propulsion to its operational orbit. Observations from orbit will go on for at least one Earth year.


This artist’s impression provides a view of the two BepiColombo spacecraft, the Mercury
Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO), in their elliptical,
polar orbits around Mercury.

The MPO will circle the planet along an orbit ranging between 400 and 1500 kilometres
distance from the surface. The MMO orbit ranges between 400 and 12000 kilometres
from the surface. The inclination and the eccentricity of these orbits are optimised for
the study of the planet and of its magnetosphere in the very-high-temperature
environment around Mercury.

Credits: ESA - C.Carreau

Operating a spacecraft in the harsh environment of Mercury represents a true technological challenge. Mercury is the closest planet to the Sun, and the direct solar radiation hitting the spacecraft is about ten times more intense than in Earth's proximity.

Furthermore Mercury's surface, whose temperature can reach up to 470°C, not only reflects solar radiation but also emits thermal infrared radiation. Therefore, the probe will have to withstand extreme thermal conditions.

This will be one of the driving factors in the probe's design - for instance, it will drive the design of the multi-layer blanket to insulate the spacecraft and of its heat radiators.


This exploded view shows BepiColombo in its cruise configuration. Visible from the bottom
are: the BepiColombo transfer module, the Mercury Planetary Orbit (MPO), the sun
shield and the Mercury Magnetospheric Orbiter (MMO).

The transfer module is provided with solar-electric propulsion and chemical propulsion
units. The former will be used during the cruise to destination; the latter will be used
after launch to boost up the orbit to the Moon's altitude for the planned lunar gravity-assist.

Credits: EADS Astrium

Note

On ESA's behalf, Astrium GmbH (Germany) is prime contractor for the procurement of the entire 'cruise- composite' spacecraft. Furthermore it provides the design and development of the attitude and orbit control subsystem, and the integration of the engineering model. Alcatel Alenia Space Italy (AAS-I) will be the co-prime contractor for the development of the MPO electrical power, thermal control and communications systems and for the integration and test activities. In the UK, EADS Astrium Ltd is co-prime contractor for the electrical and chemical propulsion system as well as the complete MPO spacecraft structure. EADS Astrium in France will develop the on-board software on the basis of the in-orbit spacecraft Rosetta, Mars Express and Venus Express.

Further to the MPO, ESA is also responsible for the whole mission design, for the launch with a Soyuz Fregat vehicle from Kourou, French Guyana, and for the cruise operations up to the insertion of the MPO and MMO into their dedicated orbits planned in 2019. Finally, ESA is responsible for the mission and scientific operations of the MPO in its orbit around Mercury.

Source: ESA - News

BepiColombo in a nutshell

A mission to Mercury

Name BepiColombo is named after Giuseppe (Bepi) Colombo (1920-1984), a scientist who studied Mercury's orbital motion in detail as well as orbits and interplanetary travel in general.

Description Consisting of two orbiting spacecraft, BepiColombo will provide the most complete exploration yet of Mercury, the innermost planet of our Solar System. The Mercury Planetary Orbiter (MPO) will map the planet, while the Mercury Magnetospheric Orbiter (MMO) will investigate its magnetosphere.


Launch Launch is scheduled for August 2013 (when the launch window will open).


Status In development.


Journey Both orbiters will be launched together on a single Soyuz-Fregat rocket from ESA's Spaceport in Kourou, French Guiana. For its journey, BepiColombo will exploit the gravity of the Moon, Earth, Venus and Mercury itself in combination with solar-electric propulsion (SEP).

During the voyage to Mercury the two orbiters and the transfer module, consisting of electric propulsion and chemical propulsion units, form one single composite spacecraft. Arrival at Mercury will be in late summer 2019, six years after launch.


Notes Most of ESA's previous interplanetary missions have been to relatively cold parts of the Solar System. BepiColombo will be the Agency's first experience of sending a planetary probe to very 'hot' regions.

The journey from Earth to Mercury is also special - the spacecraft must brake against the Sun's gravity, which increases with proximity to the Sun, rather than accelerate away from it, as it is the case with journeys to the outer Solar System.

When approaching Mercury, the side of BepiColombo facing the Sun will have to withstand incredibly high temperatures, while that facing away from the Sun incredibly cold temperatures, all at the same time.

The day side of Mercury is very hot while the night side is very cold. BepiColombo will attempt to find out if there is water ice in permanently shadowed areas (craters in polar regions).

BepiColombo is ESA's first mission in co-operation with Japan.

Source: ESA - Space Science - BepiColombo

Status
In development

Objective
One of ESA’s Cornerstone missions, it will study and understand the composition, geophysics, atmosphere, magnetosphere and history of Mercury, the least explored planet in the inner Solar System.

Mission


The BepiColombo mission consists of two individual orbiters: the Mercury Planetary
Orbiter (MPO), that will map the planet, and the Mercury Magnetospheric Orbiter
(MMO), that will investigate its magnetosphere.

BepiColombo will help reveal information on the composition and history of Mercury,
and the history and formation of the inner planets in general, including Earth.

Credits: EADS Astrium

BepiColombo will provide the best understanding of Mercury to date. It consists of two individual orbiters: the Mercury Planetary Orbiter (MPO), that will map the planet, and the Mercury Magnetospheric Orbiter (MMO), that will investigate its magnetosphere.


What’s special?

Most of ESA's previous interplanetary missions have been to relatively cold parts of the Solar System. BepiColombo will be the Agency's first experience of sending a planetary probe to very 'hot' regions. BepiColombo is an especially challenging mission because Mercury's orbit is very close to the Sun. This makes the planet difficult to observe from a distance, because the Sun is so bright. Furthermore, it is difficult to reach it and to place a spacecraft in a stable orbit around it, due to the gravity of the Sun. Scientists want to study Mercury because of the valuable clues it can provide about how planets form and interact with the Sun.

Only NASA's Mariner 10 has visited Mercury so far. It provided the only existing close-up images of the planet when it flew past three times in 1974-1975. Once BepiColombo arrives, it will help reveal information on the composition and history of Mercury, and the history and formation of the inner planets in general, including Earth.

With two spacecraft, BepiColombo is a large and costly mission - it is one of the 'cornerstones' in ESA's long-term science programme. The mission presents enormous, but exciting challenges.


Spacecraft

The BepiColombo mission is based on two spacecraft:

• a Mercury Planetary Orbiter (MPO); and
• a Mercury Magnetospheric Orbiter (MMO)

Among several investigations, BepiColombo will make a complete map of Mercury at different wavelengths. This will allow to map the planet's mineralogy and elemental composition and determine whether the interior of the planet is molten or not.


Journey

Several launch methods have been extensively studied. In the selected scenario, for its journey to destination BepiColombo will cleverly use the gravity of the Moon, Earth, Venus and Mercury itself in combination with the thrust provided by solar-electric propulsion (SEP). During the voyage to Mercury, the two orbiters and transfer module, consisting of electric propulsion and chemical propulsion units, will form one single composite spacecraft.

When approaching Mercury, the transfer module will be separated and the composite spacecraft will use conventional rocket engines and the so-called 'weak stability boundary capture technique' to bring it into polar orbit around the planet. When the MMO orbit is reached, the MPO will separate and lower its altitude by means of chemical propulsion to its operational orbit. Observations from orbit will go on for one Earth year.


History

As the nearest planet to the Sun, Mercury has an important role in showing us how planets form. Mercury, Venus, Earth and Mars make up the family of terrestrial planets, each carrying essential information to trace the history of the whole group.

The knowledge of how they originated and evolved is a key to understanding how conditions supporting life arose in the Solar System, and possibly elsewhere. As long as Earth-like planets orbiting other stars remain inaccessible to astronomers, the Solar System is the only laboratory where scientists can test models applicable to other planetary systems.

Exploring Mercury is therefore fundamental to answer important astrophysical and philosophical questions such as 'Are Earth-like planets common in the Galaxy?'

A European mission to Mercury was first proposed in May 1993. Although an assessment showed it to be too costly for a medium-size mission, ESA made a Mercury orbiter one of the three new Cornerstones missions when the Horizon 2000 science programme was extended in 1994.

Gaia competed with BepiColombo for the fifth Cornerstone mission. In October 2000, ESA approved a package of missions for 2008–2013 and both BepiColombo and Gaia were approved.


Partnerships

BepiColombo is an ESA mission in co-operation with Japan..

Source: ESA - Space Science - BepiColombo

The EADS Astrium press release is reproduced below:

© EADS Astrium

Friedrichshafen, February 26th 2007 – Astrium is set to build the Mercury probe BepiColombo on behalf of the European Space Agency, ESA. ESA’s scientific programme decision-making body, the “Science Programme Committee” (SPC) agreed to award this order to Astrium, Europe’s largest space company, following the decision of ESA’s Industrial Policy Committee in January this year. The industrial contract is worth approximately 330 million euros. BepiColombo is scheduled to begin its journey to Mercury in 2013.

BepiColombo will consist of three modules: a European orbiter, a Japanese orbiter and a transfer module carrying the two spacecraft to Mercury. The complete unit will have a height of approximately five meters and a mass of about three tonnes, of which about 50% is propellant.

The European “Mercury Planetary Orbiter“(MPO) will be equipped with eleven sophisticated scientific instruments. Flying in a polar orbit, it will study Mercury for at least a year, imaging the planet’s surface, generating height profiles, and collecting data on Mercury’s composition and atmosphere. The Japanese “Mercury Magnetospheric Orbiter” (MMO) will investigate the planet’s magnetic field with its five on-board instruments.

Astrium in Germany as prime contractor is responsible for the entire “three-section” spacecraft, leading an industrial core-team including Astrium Ltd in the UK and Alcatel Alenia Space in Italy. Attitude and orbit control design and development is also under German responsibility and the integration of the engineering model will also take place in Friedrichshafen, Germany. In the U.K., Astrium is responsible for the electrical and chemical propulsion system as well as the complete MPO spacecraft structure. Alcatel Alenia Space will develop the MPO electrical power, thermal control and communications systems and is responsible for the integration and test activities. Astrium in France will develop the on-board software building on experienced gained on Rosetta, Mars Express and Venus Express.

One of the greatest challenges facing Astrium engineers is preparing BepiColombo for the extreme temperatures it will encounter - close to Mercury, solar radiation is up to ten times stronger than on Earth, with temperatures of up to 470 degrees Celsius on the planet’s surface.

Experts at Astrium and at Alcatel Alenia Space will use a variety of techniques to protect the electronics and scientific instruments from the extreme heat including a newly designed insulating multi-layer blanket whose top layer is likely to be made using ceramic-fibres. and a radiator to release the heat from the probe’s interior into space, whose design makes it less sensitive to the thermal infared radiation emitted by the planet’s surface. In addition the spacecraft will use special solar arrays capable of supplying power even when temperatures reach 250 degrees Celsius.

The combination of a conventional chemical propulsion system with an innovative ion propulsion system will provide the required thrust on BepiColombo’s long journey. Several swing-by manoeuvres are planned to reach Mercury. During these manoeuvres, BepiColombo will be accelerated using the gravity fields of the Moon, Earth and Venus. BepiColombo is scheduled to reach its destination in 2019 and enter into a polar orbit after two further swing-by manoeuvres at Mercury.

Schedule to explore Mercury for at least 12 months, the spacecraft’s mission may be extended by a further year. To date, planetary researchers know very little about the hottest planet in our solar system. Most of the detailed data comes from NASA’s Mariner 10 spacecraft which performed three flybys in the seventies and was able to image part of the planet.

EADS Astrium, a wholly owned subsidiary of EADS, is dedicated to providing civil and defence space systems. In 2005, Astrium had a turnover of €2.7 billion and 11,000 employees in France, Germany, the United Kingdom, Spain and the Netherlands. Its three main areas of activity are: the business units Astrium Space Transportation for launchers and orbital infrastructure, and Astrium Satellites for spacecraft and ground segment, and its wholly owned subsidiary Astrium Services for the development and delivery of satellite services.

EADS is a global leader in aerospace, defence and related services. In 2005, EADS generated revenues of €34.2 billion and employed a workforce of more than 113,000.

Source: EADS Astrium

MESSENGER Mission News
March 19, 2007

MESSENGER GEARING UP TO UNDERSTAND MERCURY’S MAGNETOSPHERE

Among the primary questions driving NASA’s MESSENGER mission to Mercury are the nature and dynamics of the planet’s small, Earth-like magnetosphere and its interaction with the solar wind and Mercury’s tenuous atmosphere. The probe’s Energetic Particle and Plasma Spectrometer (EPPS) instrument will play a key role in unraveling these complex topics. For the first time in nearly two years, engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., have turned on the instrument for testing and calibration.

The team hasn’t operated the EPPS since the Earth flyby for a variety of operational reasons, including the spacecraft orientation and the available data rate during the mission cruise phase. Initially, following the Earth flyby in August 2005, the spacecraft was flying “backward” to the Sun to minimize heater power. “That put the Sun directly in the instrument’s field of view, and operating the instrument with the Sun’s ultraviolet rays shining on the detectors could damage the instrument, so EPPS was turned off,” says APL’s George Ho, the EPPS instrument scientist. “Since the first Venus flyby in October 2006, we’ve had limited telemetry; but now we are in a position to capture important data.”

PLANETARY MAGNETISM

EPPS consists of an Energetic Particle Spectrometer (EPS) sensor for energetic ions and electrons and a Fast Imaging Plasma Spectrometer (FIPS) sensor for thermal plasmas. MESSENGER’s scientists will use data collected by EPPS to understand the structure and dynamics of Mercury’s magnetosphere, critical to separating the planet’s intrinsic magnetic field from fields associated with the interaction of the magnetosphere with the solar wind.

When Mariner 10 passed by Mercury more than 30 years ago, it discovered an internal magnetic field 1% as strong as Earth’s. The source of this field is not yet understood, however, and resolving this issue is a key objective of the MESSENGER mission. As at Earth, the planet’s magnetic field diverts the solar wind to form a magnetosphere, within which Mercury’s magnetic field governs the dynamics of charged particles.

Because electric currents flowing at magnetospheric boundaries also give rise to magnetic fields, an understanding of Mercury’s magnetosphere is necessary to describe the planetary magnetic field accurately. This step is particularly important at Mercury because the planet’s field is comparatively weak and the magnetospheric contribution near the planet is comparable in strength to the intrinsic field. The energetic particle sensors provide a powerful means to map the magnetospheric boundaries and achieve this objective.

MAPPING THE MAGNETOSPHERE

EPPS will measure the mix and characteristics of charged particles in and around Mercury’s magnetosphere using EPS and FIPS, both of which are equipped with time-of-flight and energy-measurement technologies to determine particle velocities and elemental species.

From its vantage point near the top deck of the spacecraft, the APL-built EPS will observe ions and electrons accelerated in the magnetosphere. EPS has a 160° by 12° field of view for measuring the energy spectra and pitch-angle distribution of these ions and electrons.

Mounted on the side of the spacecraft, FIPS—built by the University of Michigan in Ann Arbor—will observe low-energy ions coming from Mercury’s surface and sparse atmosphere, ionized atoms picked up by the solar wind, and other solar wind components. FIPS provides nearly full hemispheric coverage.

FIPS TEST AND EPS ENERGY CALIBRATION

On March 2, instrument engineers at APL conducted a FIPS “trip point” test to ensure that the spectrometer’s temperature alarm worked. “Everything went well, the instrument did exactly what it was supposed to do,” says Ho.

Over the next several weeks, engineers will calibrate the EPS’s solid-state detectors. “It is essential that we determine the energy threshold of these detectors in the interplanetary environment,” Ho explains. “The interplanetary environment provides us a known particle distribution to put the instrument through its paces.”

Practicing at Venus

As with most MESSENGER instruments, EPPS will get a workout during the upcoming Venus flyby 2. While Venus, unlike Mercury and Earth, has no internal magnetic field, it does have an “induced magnetosphere” produced by the interaction of the solar wind with the planet’s highly conducting ionosphere. During MESSENGER’s second Venus encounter, EPPS will observe the acceleration of energetic charged particles at the planet’s bow shock and elsewhere, measurements that are used to identify the primary plasma boundaries and characterize the near-tail region.

“We’ll be getting pretty close to Venus with this flyby, to within about 300 kilometers of the surface, close enough to observe all of the regions resulting from the solar wind-Venus interaction,” says Ho. This opportunity will allow the EPPS team to try out their operations and analysis techniques for mapping Mercury’s magnetosphere prior to the first encounter with Mercury in January 2008.
FOUR YEARS AND COUNTING!

March 18 marked fours years to the day before Mercury orbit insertion. To become the first spacecraft to orbit Mercury, MESSENGER must follow a circuitous path through the inner solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury. This impressive journey will return the first spacecraft data from Mercury in more than 30 years. To explain our mission further we’ve updated the details of this journey, the MESSENGER spacecraft, and the Mission Operations Center on a redesigned section of the MESSENGER Web site, http://messenger.jhuapl.edu/the_mission/index.html. This section features the most recently completed flight path adjustment, an item that will be changed as the mission proceeds and future events are completed.

Source: JHUAPL - MESSENGER - Status Report

MESSENGER Mission News
April 2, 2007

MESSENGER COMPLETES FORTY PERCENT OF CRUISE PHASE
On March 28, MESSENGER completed 40% of its five-year cruise phase, as measured by travel time. The probe has completed one-third of its flight distance on its trip to Mercury, and its average cruise speed will continue to increase as it homes in on its ultimate target: Mercury, the closest planet to the Sun. MESSENGER’s average speed will top out at a spacecraft record of close to 63 kilometers per second (141,000 miles per hour) in mid-October 2008.

The cruise phase has been used to commission the spacecraft systems and instruments, as well as to fine tune the mission operations procedures of the team at the Johns Hopkins University Applied Physics Lab to ensure that the spacecraft and its instruments perform flawlessly at Mercury.

“The word ‘cruise’ can be misleading, because the time since launch has been quite busy and technically challenging,” says APL’s Andy Calloway, MESSENGER’s mission operations manager. “In the first 2.5 years of the mission, we have had a complete system and instrument commissioning, 10 propulsive trajectory correction maneuvers, two planetary flybys, a major processor software load, five instrument software loads, a long-duration solar conjunction period, numerous autonomy system loads, not to mention the anomalies that accompany any mission, such as an unexpected processor reset.”

An Earth flyby one year after launch and a large propulsive maneuver in December 2005 set the spacecraft on course for the first Venus flyby in October 2006. The Mercury Dual Imaging System (MDIS) acquired spectacular images of the Earth during the flyby, available at http://ser.sese.asu.edu/MESSENGER_20050802/close.html; as well as a ‘film’ of Earth as it receded in the distance, on the Web at http://ser.sese.asu.edu/MESSENGER_20050802/list_movie_01.html.

Planning is now underway to use the second Venus flyby on June 5 to complete final rehearsals for three Mercury flybys. Those flybys, assisted by four deep space maneuvers, will slow the spacecraft sufficiently for Mercury orbit injection on March 18, 2011.

The upcoming planetary encounter also offers a variety of opportunities for making new observations of Venus’ atmosphere and cloud structure, space environment, and, perhaps even the surface. All of the MESSENGER instruments will be trained on Venus during the encounter.

• The MDIS will image the night side in near-infrared bands, and color and higher-resolution monochrome mosaics will be made of both the approaching and departing hemispheres.
• The UltraViolet and Visible Spectrometer, part of the probe’s Mercury Atmospheric and Surface Composition Spectrometer (MASCS), will capture profiles of emissions from atmospheric species versus altitude on both the day and night sides as well as observations of the exospheric tail on departure.
• MASCS’s Visible and InfraRed Spectrograph will observe the planet near closest approach to assess the chemical composition of clouds. It may also detect near-infrared returns from the surface.
• The MESSENGER Laser Altimeter (MLA) will measure Venus’ brightness at 1064-nm by using its pulse return detector as a passive sensor. MLA will also pulse its laser in an attempt to measure the range to one or more cloud decks for several minutes near closest approach.
• The Magnetometer will characterize the magnetic structure of the Venus bow shock and draping of the interplanetary magnetic field over Venus’ ionosphere while the Energetic Particle and Plasma Spectrometer will observe charged particle acceleration and plasma flows associated with the bow shock.

The Venus Express mission of the European Space Agency is currently operating in an elliptical polar orbit about Venus, and MESSENGER’s June planetary encounter together with the ongoing observations by Venus Express will permit unique observations of the Venus-solar wind interaction. To understand fully how the solar wind plasma affects and controls the Venus ionosphere and nearby plasma dynamics, simultaneous measurements are needed of the interplanetary conditions and the particle-and-field environment at Venus. The combined MESSENGER and Venus Express observations will be the first opportunity to conduct such two-spacecraft measurements.

The Mercury flybys, in January and October 2008 and September 2009, will be used to provide initial maps of the hemisphere of the planet never before seen by spacecraft, as well as the first mineralogical data on Mercury's surface.

Calloway says the remaining sixty percent of the cruise phase will be equally challenging, “But even more rewarding because now we will be collecting information at Mercury that no one has ever seen before.”

A PLANETARY GEOLOGIST KEEPS HER EYE ON THE PLANETS

As the lead instrument scientist for MESSENGER’s Mercury Dual Imaging System (MDIS), Louise Prockter is all set to train her keen eye on images of Venus during the spacecraft’s second flyby of that planet in June that will send it onward to Mercury. But in her early years, studying the surface of planets was the farthest thing from her mind. Find out how she got her start in geophysics in her profile, online at http://messenger.jhuapl.edu/who_we_are/member_focus.html.

STAT CORNER

Now 972 days after launch, MESSENGER is about 53.4 million miles (86.7 million kilometers) from the Sun and 135.3 million miles (217.7 kilometers) from Earth. At that distance, a signal from Earth reaches the spacecraft in 12 minutes and six seconds. The spacecraft is moving around the Sun at 95,841 miles (154,241 kilometers) per hour. MESSENGER's onboard computers have executed 255,719 commands from mission operators since launch on August 3, 2004.

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.

Source: JHUAPL - MESSENGER - Status Report

I wonder if there is any ice on Mercury?.........B

Photo of planet Mercury, obtained with NASA's Mariner 10 spacecraft
http://www.vt-2004.org/mt-2003/mt-mercury.html

It is not impossible that in some of the polar craters there are regions which are always in shadow. It is possible that there could be some ice there (as has been hypothesised for the Moon).

In 1991 radar signals from 230ft Goldstone radiotelescope suggested that such ice may actually exist at the planet's North Pole. Click here for National Radio Asronomy Obsrvatory article. This is one of the questions that should be answered by MESSENGER and BepiColombo.

However the day time temperature for the rest of Mercury reaches more than 400^oC (750^oF). As these temperatures ar high enough to melt tin and zinc there is no chance of ice elsewhere on the planet.

MESSENGER Mission News
May 2, 2007

MESSENGER LINES UP FOR SECOND PASS AT VENUS
The MESSENGER trajectory correction maneuver (TCM-15) completed on April 25 lasted 140 seconds and adjusted the spacecraft's velocity by 0.568 meters per second (1.86 feet per second). One more course correction will be performed before the probe’s second Venus flyby on June 5 to ensure precise targeting of the gravity assist.

The maneuver started at 1:30 p.m. EDT. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of TCM-15 about 10 minutes later, when the first signals indicating thruster activity reached NASA’s Deep Space Network tracking station outside Madrid, Spain.

Although this maneuver was designed to adjust MESSENGER’s velocity by 0.767 meters per second (2.52 feet per second), mission controllers estimated that about 26% less than the intended velocity change was achieved. There was almost no error in the direction for the velocity change. “The result is that the current trajectory aim point is about 200 kilometers, or 124.3 miles, higher than the ideal target point for the flyby,” explains APL’s Eric Finnegan, the MESSENGER mission systems engineer.

According to Finnegan, the spacecraft orientation began to jitter slightly shortly into the maneuver. The spacecraft responded properly by pulsing other thrusters to maintain accurate pointing through the TCM, but this pulsing reduced the efficiency of the maneuver.

“The spacecraft compensated properly for the attitude oscillation, but because of the additional thrusting activity, the system would have needed more time to produce the commanded velocity adjustment,” he says. “As a safety precaution in all MESSENGER maneuvers, the team determines the maximum expected maneuver time and instructs the spacecraft to shut the maneuver down if that time is exceeded. That’s what happened here, so the maneuver was stopped before it reached 100% of the planned velocity change.”

The flight team is analyzing the data from the attitude control system and tracking data to identify what caused the jitter so they can design future maneuvers to avoid it. Although TCM-15 resulted in a shortfall, it was sufficiently successful that a contingency maneuver, held in reserve for May 5, is not needed. The team can accommodate all adjustments in TCM-16, scheduled for May 25, to direct the spacecraft to the intended aim point 337 kilometers (209 miles) above the surface of Venus.

For graphics of MESSENGER's orientation during the maneuver, visit the “Trajectory Correction Maneuvers” section of the mission Web site at
http://messenger.jhuapl.edu/the_mission/tcm15.html.

MESSENGER CO-INVESTIGATOR NAMED TO NATIONAL ACADEMY OF SCIENCES

MESSENGER Co-Investigator Mario Acuña, a senior astrophysicist and project scientist with the International Solar Terrestrial Physics Program at NASA Goddard Space Flight Center, was among the 72 new members appointed to the National Academy of Sciences. The election was held May 1 during the business session of the 144th annual meeting of the Academy. Those elected bring the total number of active members to 2,025.

Acuña is an expert in planetary magnetic fields and has been involved in numerous space missions. He is a member of MESSENGER’s Atmosphere and Magnetosphere Group and will help analyze data from the probe’s Magnetometer. As a member of the Academy, Acuña he 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.

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.

Source: JHUAPL - MESSENGER - Status Report

Researchers working with high-precision planetary radars, including the Goldstone Solar System Radar of NASA's Jet Propulsion Laboratory, Pasadena, Calif., have discovered strong evidence that the planet Mercury has a molten core. The finding explains a more than three-decade old planetary mystery that began with the flight of JPL's Mariner 10 spacecraft. The research appears in this week's issue of the journal Science.

Launched in Nov. 1973, Mariner 10 made three close approaches to Mercury in 1974 and 75. Among its discoveries was that Mercury had its own weak magnetic field - about one percent as strong as that found on Earth.


Image above: Diagram showing the interior
structure of Mercury. The metallic core
extends from the center to a large fraction
of the planetary radius. Radar observations
show that the core or outer core is molten.
Image credit: Nicolle Rager Fuller,
National Science Foundation
+ Larger view
+ High resolution JPEG (553Kb)

"Scientists had not expected to find a magnetic field at Mercury," said Professor Jean-Luc Margot of Cornell University, Ithaca, N.Y., leader of the research team. "Planetary magnetic fields are associated with molten cores, and the prevailing theory was the planet was too small to have a molten core."

Scientists theorized that Mercury consisted of a silicate mantle surrounding a solid iron core. This iron was considered solid - or so the theory went - because small planets like Mercury cool off rapidly after their formation. If Mercury followed this pattern, then its core should have frozen long ago.

Many believed the Mercury mystery would only be resolved if and when a spacecraft landed on its aggressively toasty surface. Then, in 2002, scientists began pointing some of the most powerful antennas on our planet at Mercury in an attempt to find the answer.

"On 18 separate occasions over the past five years, we used JPL's Goldstone 70-meter [230-foot] antenna to fire a strong radar signal at Mercury," said Planetary Radar Group Supervisor Martin Slade of JPL, a co-author of the paper. "Each time, the radar echoes from the planet were received about 10 minutes later at Goldstone and another antenna in West Virginia."

Measuring the echo of particular surface patterns from the surface of Mercury and how long they took to reproduce at both Goldstone and the Robert C. Byrd Green Bank Telescope in West Virginia allowed scientists to calculate Mercury's spin rate to an accuracy of one-thousandth of a percent. The effect was also verified with three more independent radar observations of Mercury transmitted from the National Science Foundation's Arecibo Observatory in Puerto Rico.


Image above: Artistic rendering of the
observational geometry. A radar signal
(yellow) is transmitted from the Goldstone
antenna in California. Radar echoes (red)
are received at the Goldstone antenna and
at the Robert C. Byrd telescope in Green Bank,
West Virginia.
Image credit: Bill Saxton, NRAO/AUI/NSF
+ Larger view
+ High resolution JPEG (911Kb)

With these data the science team was able to detect tiny twists in Mercury's spin as it orbited the sun. These small variations were double what would be expected for a completely solid body. This finding ruled out a solid core, so the only logical explanation remaining was that the core - or at the very least the outer core - is molten and not forced to rotate along with its shell.

Maintaining a molten core over billions of years requires that it also contain a lighter element, such as sulfur, to lower the melting temperature of the core material. The presence of sulfur supports the idea that radial mixing, or the combining of elements both close to the sun and farther away, was involved in Mercury's formation process.

"The chemical composition of Mercury's core can provide important clues about the processes involved in planet formation," said Margot. "It is fundamental to our understanding of how habitable worlds -- planets like our own -- form and evolve."

Mercury still has its share of mysteries. Some may be solved with the NASA spacecraft Messenger, launched in 2004 and expected to make its first Mercury flyby in 2008. The spacecraft will then begin orbiting the planet in 2011. “It is our hope that Messenger will address the remaining questions that we cannot address from the ground,” said Margot.

The study's other co-authors include Stan Peale of the University of Santa Barbara in California; Raymond Jurgens, a JPL engineer, and Igor Holin of the Space Research Institute in Moscow, Russia.

The Goldstone antenna is part of NASA's Deep Space Network Goldstone station in Southern California's Mojave Desert. Goldstone's 70-meter diameter antenna is capable of tracking a spacecraft traveling more than 16 billion kilometers (10 billion miles) from Earth. The surface of the 70-meter reflector must remain accurate within a fraction of the signal wavelength, meaning that the precision across the 3,850-square-meter (41,400-square-foot) surface is maintained within one centimeter (0.4 inch).

For more information about NASA and agency programs on the Internet, visit:

http://www.nasa.gov


Media contact: DC Agle/Carolina Martinez 818-393-9011/354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown/Tabatha Thompson 202-358-1726/3895
NASA Headquarters, Washington

2007-050

Source: NASA - Exploring the Universe - Our Solar System

MESSENGER Mission News
May 25, 2007
http://messenger.jhuapl.edu

MESSENGER ZEROS IN ON VENUS

The MESSENGER trajectory correction maneuver (TCM-16) completed on May 25 lasted 36 seconds and adjusted the spacecraft’s velocity by 0.212 meters per second (0.696 feet per second). The movement targeted the spacecraft close to the intended aim point 337 kilometers (209 miles) above the surface of Venus for the probe’s June 5 flyby of that planet.

The maneuver started at 12:00 p.m. EDT. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of TCM-16 about 7 minutes later, when the first signals indicating thruster activity reached NASA’s Deep Space Network tracking station outside Madrid, Spain.

“Today’s operation completed just as planned,” says Mission Operations Manager Andy Calloway of APL. “All subsystems were nominal going into the maneuver, and the burn cutoff occurred right at the expected time. Now that TCM-16 is behind us, we are focused on loading the Venus flyby command load to the spacecraft next week.”

For graphics of MESSENGER's orientation during the maneuver, visit the “Trajectory Correction Maneuvers” section of the mission Web site at http://messenger/the_mission/maneuvers.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.

Source: JHUAPL - MESSENGER - Status Report

MEDIA ADVISORY: M07-060
June 1, 2007
http://messenger.jhuapl.edu

WATCH VENUS AND MERCURY THIS WEEK (AND IMAGINE MESSENGER FLYING BY VENUS)

In the coming evenings, sky watchers can acquaint themselves with the MESSENGER spacecraft mission to Mercury. Late afternoon on Tuesday, June 5, 2007, MESSENGER will fly within about 210 miles (340 kilometers) of the surface of the planet Venus, and get a gravity kick toward its ultimate destination, the sun-baked planet Mercury.

Both Venus and Mercury will be well-placed for viewing during dusk the week before MESSENGER's encounter with Venus. Go to a location away from bright lights with a good view of the western and northwestern horizon. Venus is the brilliant "evening star" fairly high above the western horizon. Forty-five minutes after sunset (or between 8:45 p.m. and 9:45 p.m. Daylight Time, depending on your location within your time zone), you should start to see other bright stars and planets as the sky darkens.

To the right of Venus is the star Pollux, and an equal distance farther to the right is Castor. These “twins” are the brightest stars in the constellation Gemini. The planet Mercury will be similar to Pollux in apparent brightness, located close to the horizon almost directly below Castor in the west-northwest. Another way to estimate the location of Mercury is to find the planet Saturn to the upper left of Venus. Mercury is a similar distance away from Venus but to the lower right. Find it quickly, before it sets. (These instructions are roughly correct for the evenings of June 1-5, 2007).

MESSENGER (which is much too small and faint to see) is approaching Venus from the right. You can imagine MESSENGER about a third of the way from Venus to Pollux (about four Moon diameters from Venus) tonight; the Moon will be rising in the east. By the evening of June 4, MESSENGER will be closing in on Venus, just two-thirds of the Moon’s diameter away. MESSENGER flies by Venus before sunset as seen from the United States on June 5. But two hours later, as the sky darkens and Venus gleams in the west, the spacecraft will still be an imperceptible distance to the left of Venus, with its motion slightly changed so that it is accurately on course for its first flyby of Mercury in January 14, 2008.

This is a good time to try to see MESSENGER’s elusive target, Mercury, which is always a challenge to spot since it stays so close to the Sun. Look for it on the first clear evening, because it fades rapidly during the first two weeks of June, moving ever closer to the Sun. (Through a telescope, one can see Mercury’s phase changing from half-phase to crescent.)

MESSENGER will be making scientific measurements of Venus, as well as testing out its instruments for Mercury, as it zooms by Earth’s sister planet late Tuesday afternoon.

Clark R. Chapman, cchapman@boulder.swri.edu
Member, MESSENGER Science Team

Source: JHUAPL - MESSENGER - Status Report

The press release is reproduced below:

June 4, 2007

Tabatha Thompson
Headquarters, Washington
202-358-3895

Paulette Campbell
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-6792

RELEASE: 07-129

NASA Spacecraft Ready for Science-Rich Encounter With Venus

WASHINGTON - NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft will make its closest pass to Venus on Tuesday, June 5. This will place the spacecraft on target for a flyby of Mercury in January 2008. MESSENGER will be the first probe to visit the innermost planet in more than 30 years.

Threading its path through an aim point 209 miles above the surface of Venus, MESSENGER will use the pull of the planet's gravity to guide it closer to Mercury. During this flyby, Venus's gravity will change the spacecraft's direction around the sun and decelerate it from 22.7 to 17.3 miles per second.

"Typically, spacecraft have used planetary flybys to speed toward the outer solar system," said Andy Calloway, MESSENGER mission operations manager, Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md. "MESSENGER, headed in the opposite direction, needs to slow down enough to slip into orbit around Mercury."

This will be MESSENGER's second pass by Venus. During its first flyby of the planet, in October 2006, no scientific observations were made. Venus was at superior conjunction, placing it on the opposite side of the sun from Earth, leading to a two-week radio contact blackout between the spacecraft and its operators. This upcoming encounter offers opportunities for new observations of Venus's atmosphere, cloud structure, space environment and perhaps even its surface. The spacecraft will train most of its instruments on Venus during the upcoming encounter.

"During the flyby we'll ensure that the spacecraft and payload remain healthy, calibrate several of the science instruments, and practice many of the observations planned for the Mercury flybys," said Sean Solomon, MESSENGER principal investigator and planetary scientist at the Carnegie Institution of Washington.

The team plans to image the upper cloud layers at visible and near-infrared wavelengths for comparison with earlier spacecraft observations. Magnetic field and charged particle observations will be made to characterize the solar wind interaction with Venus and search for solar wind pick-up ions. Ultraviolet-visible and X-ray spectrometry will permit detailed observations of the composition of the upper atmosphere, and MESSENGER will search for lightning on the Venus night side.

MESSENGER will join the European Venus Express spacecraft, currently orbiting Venus, to make new observations of the Venus environment. To understand fully how solar wind plasma affects and controls the Venus ionosphere and nearby plasma dynamics, simultaneous measurements are needed of the interplanetary conditions and the particle-and-field characteristics at Venus. The combined MESSENGER and Venus Express observations will be the first opportunity to conduct such two-spacecraft measurements.

"By coordinating and comparing these observations, we will be able to maximize the science from both missions and potentially learn things that would not be revealed by one set of observations alone," said APL's Ralph McNutt, MESSENGER project scientist.

MESSENGER is only the second spacecraft to set sights on Mercury. NASA's Mariner 10 sailed past the planet three times in 1974 and 1975 and took detailed images of about 45 percent of the surface. Carrying seven scientific instruments on its compact and durable composite frame, MESSENGER will provide the first images of the entire planet. The mission also will collect detailed information on the composition and structure of Mercury's crust, its geologic history, the nature of its thin atmosphere and active magnetosphere, as well as the makeup of its core and polar materials.

Launched in August 2004, MESSENGER has completed more than 40 percent of its 4.9-billion mile journey to Mercury, which includes 15 loops around the sun. An Earth flyby one year after launch and a large propulsive maneuver in December 2005 set the spacecraft on course for the first Venus flyby in October 2006.

Next up for MESSENGER is a trio of swings past Mercury, in January and October 2008 and September 2009. During these flybys, the probe will map most of the planet and determine surface and atmospheric composition. These data will be used to help plan priorities for the yearlong orbital mission, which begins in March 2011.

The MESSENGER project is the seventh in NASA's Discovery Program of lower-cost, scientifically focused space missions. The Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages the mission for NASA's Science Mission Directorate, Washington.

For the latest news and images about the MESSENGER mission, visit:

http://www.nasa.gov/messenger

- end -

--------------------------------------------------------------------------------

Source: NASA Press Release 07-129

Media Contact:
Paulette W. Campbell
(240) 228-6792 or (443) 778-6792
paulette.campbell@jhuapl.edu

MESSENGER Completes Second Flyby of Venus,
Makes Its Way toward Fir