MESSENGER: Three Days to Mercury!

http://messenger.jhuapl.edu/news_room/status_report_01_11_08.html

MESSENGER Mission News
January 11, 2008

Three Days to Mercury!

The countdown to the first flyby of Mercury by the MESSENGER
spacecraft
has begun. Sunday morning, MESSENGER will start recording the evidence
of this historic event. At 8 a.m. EST on January 13 - 30 hours before
the closest approach to Mercury - the spacecraft will turn its main
antennas away from Earth and automatically begin executing the 5,000
on-board stored commands.

"The entire instrumentation suite will be operating during this flyby,
taking more than 1,200 images and gathering other scientific
observations, filling the on-board data recorder with more than 700
megabytes of history-making measurements, within a period of 55
hours,"
said MESSENGER Systems Engineer Eric Finnegan of the Johns Hopkins
University Applied Physics Laboratory (APL) in Laurel, Md. "Fifty
minutes prior to closet approach, signals from the spacecraft will go
quiet as MESSENGER passes behind Mercury, out of Earth's view.
Forty-eight minutes later, engineers and scientists on the ground will
attempt to witness the gravitational pull of the planet first-hand by
re-acquiring the transmitted signal from the spacecraft within minutes
of the closet approach point."

On Tuesday, January 15, at noon EST, 22 hours after the flyby,
MESSENGER
will take one last look at Mercury before turning back to Earth to
start
returning the treasures stored on-board. "Complicating this sequence
of
events is the demanding requirement to conduct all observations by the
spacecraft behind the safety of MESSENGER's sunshade," Finnegan said.
"Conducting this encounter at 30 million miles from the Sun, almost
two-thirds closer than the Earth, would have been impossible in the
era
of Mariner 10. But thanks to advances in material sciences,
MESSENGER's
electronics and sensitive instruments can run at room temperature
behind
the sunshade, while the front surface temperature rises to more than
600° F."

Notwithstanding the operational and scientific importance of this
flyby,
MESSENGER is only slightly more than halfway along its six-and-one-
half
year, 4.9 billion-mile journey between its launch in August 2004 and
orbit insertion around Mercury in March 2011. "Over the next 12-month
period, the MESSENGER team will engage in the most grueling year of
operations since launch, executing two planetary encounters, two deep
space maneuvers, and possibly six additional maneuvers - using the
smaller thrusters of the on-board propulsion system - to keep the
spacecraft on course," added Finnegan.

The primary goal of this flyby is to obtain a gravity assist from the
planet, which will reduce the arrival velocity of the spacecraft for
orbit insertion in March 2011. "Slowing the spacecraft by 5,000 miles
per hour, MESSENGER's orbital period around the Sun will be decreased
by
11 days, thus setting up a planetary car race with Mercury," Finnegan
said. "Using its internal engine and future gravity assists, the
spacecraft, after being lapped by Mercury many times in this race
around
the Sun, will ultimately match the 88-day orbital period of the
innermost planet."

To facilitate this change in velocity, the spacecraft will speed over
the uncharted surface of Mercury at a relative velocity of more than
16,000 miles per hour and pass within 124 miles of the surface, the
closest any man-made object has been to this planet. During this
close
approach, the spacecraft will experience a period of 14 minutes
without
solar power, where operations will rely only on the spacecraft's
internal batteries.

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

New Optical Navigation Image of Mercury Available

MESSENGER continues to speed toward Mercury, preparing for its closest
approach to the planet on Monday, January 14, 2008, at 19:04:39 UTC
(2:04:39 pm EST). This image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
gallery_id=2&image_id=109&preview=Y>
was snapped with the Narrow Angle Camera, one half of MESSENGER's
Mercury Dual Imaging System (MDIS), on January 10, 2008, when
MESSENGER
was less than 2 million kilometers (1.2 million miles) from the
planet.
Mercury is about 4,880 kilometers (3,030 miles) in diameter, and this
image has a resolution of about 50 kilometers/pixel (31 miles/pixel).

As the spacecraft continues toward closest approach, additional
information and features will be available online at
http://messenger.jhuapl.edu/mer_flyby1.html, so check back frequently.
Following the flyby, be sure to check back to see the latest released
images and science results!

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

An Ode to MESSENGER's First Mercury Pass

Stuart Atkinson, a writer and amateur astronomer from the Lake
District
of England, has written a poem, "The MESSENGER Approaches
<http://messenger.jhuapl.edu/poem.html>," to commemorate MESSENGER's
first flyby of Mercury. Atkins is the author of six children's
astronomy
books - with more to be published this year. He is also the secretary
of
the Cockermouth Astronomical Society, which he founded 10 years ago,
and
is a regular commentator on BBC Radio Cumbria's
<http://www.bbc.co.uk/england/radiocumbria> Friday evening show.

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

Farewell to a Fellow Explorer

The MESSENGER team notes with sadness the passing earlier today of Sir
Edmund Hillary, who with Tenzing Norgay climbed to the summit of Mount
Everest for the first time in 1953. "We have lost one of the world's
great explorers," offers MESSENGER Principal Investigator Sean Solomon
of the Carnegie Institution of Washington. "But we take some comfort
in
that fact that we are poised nearly on the eve of exploring huge
portions of the surface of one of Earth's neighboring planets that
have
never before been seen at close range. Clearly the spirit of
exploration
that Hillary and Norgay epitomized lives on today."

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

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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