NASA’s first trip to Mercury in 30 years — and the
closest look ever at the innermost planet — starts in August
with the predawn launch of the MESSENGER spacecraft from Cape
Canaveral Air Force Station, Fla.
MESSENGER will conduct an in-depth study of the sun’s closest
neighbor, the least explored of the terrestrial (“rocky”)
planets that also include Venus, Earth and Mars. After a
scheduled 2:16 a.m. EDT liftoff aboard a Delta II launch
vehicle on Aug. 2, the first day of a 13-day launch period,
MESSENGER’s voyage includes three flybys of Mercury in 2008
and 2009 and a year-long orbit of the planet starting in
March 2011.
“Our missions to Mars and Venus have produced exciting data
and new theories about the processes that formed the inner
planets,” said Orlando Figueroa, director of the Solar System
Exploration Division at NASA Headquarters, Washington. “Yet
Mercury still stands out as a planet with a fascinating story
to tell. MESSENGER should complete the detailed exploration
of the inner solar system — our planetary backyard — and
help us to understand the forces that shaped planets like our
own,” he added.
MESSENGER (short for MErcury Surface, Space ENvironment,
GEochemistry, and Ranging) is only the second spacecraft to
set sights on Mercury. Mariner 10 sailed past it three times
in 1974 and 1975 and gathered detailed data on less than half
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 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.
MESSENGER’s science team will shape its investigation around
several questions, including: 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 near 450 degrees Celsius (840 F), have what
appears to be ice in its polar craters?
“For nearly 30 years we’ve had questions that couldn’t be
answered until technology and mission designs caught up with
our desire to go back to Mercury,” said Dr. Sean C. Solomon,
MESSENGER principal investigator, from the Carnegie
Institution of Washington. “Now we are ready. The answers to
these questions will not only tell us more about Mercury, but
illuminate processes that affect all the terrestrial
planets,” he said.
Mercury’s proximity to the sun makes it both a fascinating
subject and an unprecedented mission design challenge. The
sun can be up to 11 times brighter than what we see on Earth,
and surface temperatures at Mercury’s equator can reach 450
C, but MESSENGER will operate at room temperature behind a
sunshade of heat-resistant ceramic fabric. The 1.2-ton
spacecraft also features a heat-radiation system and will
pass only briefly over Mercury’s hottest regions, limiting
exposure to the intense heat bouncing back from the broiling
surface.
“We’re doing something no one has ever tried before,” said
MESSENGER Project Manager David G. Grant, of the Johns
Hopkins University Applied Physics Laboratory (APL), Laurel,
Md. “After launch and a long trip through the inner solar
system, we still face the risky and difficult job of orbiting
the planet next to the sun. The team is confident the
spacecraft they designed, built and tested is ready for this
journey and its mission to Mercury,” he added.
On a 4.9-billion mile (7.9-billion kilometer) journey that
includes 15 loops around the sun, the solar-powered MESSENGER
will fly past Earth once, Venus twice and Mercury three times
before easing into orbit around its target planet. The Earth
flyby, a year after launch, and the Venus flybys, in October
2006 and June 2007, use the pull of the planets’ gravity to
guide MESSENGER toward Mercury’s orbit. The Mercury flybys in
January 2008, October 2008 and September 2009, fine-tune and
slow MESSENGER’s track while allowing the spacecraft to
gather data critical to planning the mission’s orbit phase.
The MESSENGER project is the seventh in NASA’s Discovery
Program of lower-cost, scientifically focused space missions.
Solomon leads the mission as principal investigator; APL
manages the mission for NASA’s Office of Space Science and
designed, built and will operate the MESSENGER spacecraft.
For additional information about MESSENGER on the Internet,
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