MESSENGER Gains Speed

http://messenger.jhuapl.edu/news_room/details.php?id=113

MESSENGER Mission News
October 15, 2008

MESSENGER Gains Speed

Shortly after 4 a.m. this morning, MESSENGER reached its greatest
speed
relative to the Sun. The spacecraft, nearly 70% closer to the Sun than
Earth, was traveling nearly 140,880 miles per hour (62.979 kilometers
per second) relative to the Sun. At this speed MESSENGER would
traverse
the distance from Earth to Earth's Moon in only 1.7 hours!

Even at this great speed MESSENGER is slightly slower than the fastest
spacecraft: Helios 2. That spacecraft - launched into a solar orbit on
January 15, 1976 - reached a top speed of 157,078 miles per hour
(70.220
kilometers per second) relative to the Sun in April of 1976.

Because of MESSENGER's near-perfect Mercury flyby trajectory on
October
6, the mission design and navigation team decided that a
trajectory-correction maneuver (TCM) scheduled for October 28 will not
be needed. The next maneuver for the mission, scheduled to be carried
out in two parts on December 4 and December 8, will re-target the
spacecraft for the third and final encounter with Mercury in just
under
a year on September 29, 2009.

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

New Color Images of Mercury Available

The MESSENGER Science Team has released five new images from the
probe's
second flyby of Mercury. To the human eye, Mercury shows little color
variation, especially in comparison with a colorful planet like Earth.
But when images taken through many color filters - such as the 11
narrow-band color filters on the Mercury Dual Imaging System's Wide
Angle Camera (WAC) - are used in combination, differences in the
properties of Mercury's surface can create a strikingly colorful view
of
the innermost planet.

Here are four images
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
gallery_id=2&image_id=234>
of Mercury. The image in the top left is the previously released
grayscale monochrome image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
page=2&gallery_id=2&image_id=214>
taken with a single (430 nanometer) WAC filter; the remaining three
images are three-color composites, produced by placing the same three
WAC filter images with peak sensitivities at 480, 560, and 630
nanometers in the blue, green, and red channels, respectively. Shown
here <
http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=235>
are two color images of Tha-kur, named for the Bengali poet, novelist,
and Nobel laureate influential in the late 19th and early 20th
centuries.

In both the optical navigation images
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
page=3&gallery_id=2&image_id=213>
and the full-planet WAC approach frame
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
page=2&gallery_id=2&image_id=216>,
a bright feature is clearly visible in the northern portion of the
crescent-shaped Mercury. This Narrow Angle Camera (NAC) image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
gallery_id=2&image_id=236>
resolves details of this bright feature, showing that it surrounds a
small crater about 30 kilometers (19 miles) in diameter, seen nearly
edge on.

This pair of images
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
gallery_id=2&image_id=237>
illustrates the dramatic effect that illumination and viewing geometry
(i.e., the angle at which Sunlight strikes the surface, and the angle
from which the spacecraft views the surface) has on the appearance of
terrain on Mercury. And this NAC image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
gallery_id=2&image_id=238>,
taken about 85 minutes after MESSENGER's closest approach during the
mission's second Mercury flyby, shows a view of Astrolabe Rupes, named
for the ship of the French explorer Jules Dumont d'Urville. Rupes is
the
Latin word for cliff.

________________________________________

Additional information and features from this encounter will be
available online at http://messenger.jhuapl.edu/mer_flyby2.html, so
check back frequently to see the latest released images and science
results!

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

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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