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MESSENGER Lines Up For Its Second Venus Flyby

Subject: MESSENGER Lines Up For Its Second Venus Flyby
From:
Date: 3 Dec 2006 20:39:06 -0800
Newsgroups: sci.astro, alt.sci.planetary
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 today
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 41.7B0 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 5B0 of sky and fits within the
approximate 6B0 field of view of ordinary binoculars.

Space.com <http://www.space.com/spacewatch/061201_night_sky.html>  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 1B0 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 August 3, 2004, and
after flybys of Earth, Venus, and Mercury will start a yearlong study
of
its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie
Institution of Washington, leads the mission as principal investigator.

The Johns Hopkins University Applied Physics Laboratory built and
operates the MESSENGER spacecraft and manages this Discovery -class
mission for NASA.


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