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MESSENGER Mission News
December 2, 2006
http://messenger.jhuapl.edu

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.


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 Aug. 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 the Discovery-class mission for NASA.


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