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Posted by baalke on June 6, 2007, 11:52 am
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http://messenger.jhuapl.edu/news_room/status_report_06_05_07.html
Media Contact:
Paulette W. Campbell
(240) 228-6792 or (443) 778-6792
paulette.campbell@jhuapl.edu
This press release has been updated from the original version issued
6-5-07.
------------------------------------------------------------------------
MESSENGER Completes Second Flyby of Venus,
Makes Its Way toward First Flyby of Mercury in 33 Years
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging
(MESSENGER) spacecraft swung by Venus for the second time early this
evening for a gravity assist that shrank the radius of its orbit
around
the Sun, pulling it closer to Mercury. At nearly 15,000 miles per
hour,
this change in MESSENGER's velocity is the largest of the mission.
Mission operators at the Johns Hopkins University Applied Physics
Laboratory (APL) in Laurel, Md., said MESSENGER's systems performed
flawlessly as the spacecraft sped over the cloud tops of Venus at a
relative velocity of more than 30,000 miles per hour, passing within
210
miles of the surface of the planet at 23:08 UTC (7:08 p.m. EDT).
For 20 minutes during this closest approach, MESSENGER was within the
shadow of Venus, and in the absence of solar power the probe relied
solely on its internal battery. By 1:32 UTC (9:32 p.m. EDT) the
battery
had fully recharged, and the spacecraft was operating as planned. "The
biggest milestone for mission operations was first acquisition of
telemetry following closest approach, and confirmation that the
battery
was fully recharged following the 20-minute solar eclipse," said APL's
Andy Calloway, MESSENGER's mission operations manager. "We will be
monitoring recorder playback beginning June 7 to make sure all of the
files and images are fully downlinked. Next stop, Mercury on January
14,
2008!"
This second Venus flyby was a critical mission milestone in the
probe's
circuitous journey toward Mercury orbit insertion, declared MESSENGER
principal investigator Sean Solomon, from the Carnegie Institution of
Washington. "Not only did the maneuver sharpen the spacecraft's aim
toward the first encounter with Mercury in more than three decades, it
presented a special opportunity to calibrate several of our science
instruments and learn something new about Earth's nearest neighbor."
PAYLOAD WORKOUT
According to APL's Eric Finnegan, MESSENGER systems engineer, the
spacecraft's approach geometry is similar to that for the first
Mercury
flyby, allowing - for the first time in flight - the craft's seven
instruments to be turned on and operated collectively in
science-observing mode, just as they will be for Mercury. "Gathering
approximately six gigabits of data, the spacecraft will take more than
630 images, as well as make other scientific observations over the
next
few days," Finnegan said.
The team plans to image the upper cloud layers at visible and
near-infrared wavelengths for comparison with earlier spacecraft
observations. Magnetic field and charged particle observations will be
made to characterize solar wind interaction and search for solar wind
pick-up ions. Ultraviolet (UV)-visible and X-ray spectrometry will
permit detailed observations of the composition of the upper
atmosphere,
and MESSENGER will search for lightning on the Venus night side.
"We are very excited with this next step in reaching our ultimate
destination, Mercury," says APL's Ralph McNutt, MESSENGER project
scientist. "The data acquired with all of the instruments should begin
arriving back at the Deep Space Network tracking stations just after
12
p.m. EST on June 7, with more data coming down during the next few
days.
By June 8, we should have our color mosaic, as well as our laser
altimeter observations; and these will be critical to beginning
several
of the collaborative studies with our scientific colleagues on the
Venus
Express team."
During this Venus encounter, MESSENGER joined forces with the European
Space Agency's Venus Express spacecraft, currently orbiting Venus, to
make joint observations of the Venus environment. "Although Venus'
atmospheric interaction with the solar wind was studied extensively by
Pioneer Venus Orbiter in the 1980s, there has never before been an
opportunity to measure simultaneously both interplanetary conditions
and
the particle-and-field characteristics at Venus," says McNutt. "The
combined MESSENGER and Venus Express observations will be the first
opportunity to conduct such two-spacecraft measurements and should
enable advances in our overall understanding of this interaction."
NEXT UP, MERCURY!
Next up for MESSENGER is a trio of swings past Mercury in January and
October 2008 and September 2009. During these flybys, MESSENGER will
map
most of the planet and determine surface and atmospheric composition;
these data will be used to help plan priorities for the yearlong
orbital
mission, which begins in March 2011.
"The spacecraft and its operations team are poised to embark on the
most
intensive period of trajectory activities of the mission," says
Finnegan. "Over the next 18 months, the spacecraft will travel on a
veritable inner-planetary roller coaster. Three passive gravity
assists
will be conducted, one by Venus and two by Mercury. Three Deep Space
maneuvers will also be executed, using the large main engine of the
spacecraft. In addition, 13 maneuvers utilizing smaller thrusters are
possible in the event that periodic corrections to the trajectory are
necessary along the way. All told, this adds up to a very high tempo
of
operations."
MESSENGER Project Manager Dave Grant, of APL, says the work of the
MESSENGER team of engineers and scientists in completing this second
Venus flyby has been outstanding. "Our adherence to the designed
mission
trajectory and demonstrated performance of the science payload lends
confidence to the ultimate success of the MESSENGER mission, and
critical experience has been gained for managing future flybys and
eventual orbit insertion at Mercury," Grant says.
The MESSENGER project is the seventh in NASA's Discovery Program of
lower-cost, scientifically focused space missions. APL built and
operates the MESSENGER spacecraft and manages the mission for NASA's
Science Mission Directorate, Washington. For the latest news and
images
about the MESSENGER mission, visit:http://messenger.jhuapl.edu/.
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