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Posted by baalke on April 2, 2007, 12:29 pm
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http://messenger.jhuapl.edu/news_room/status_report_04_02_07.html
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
<http://ser.sese.asu.edu/MESSENGER_20050802/list_movie_01.html>, 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.
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