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Science Forum Index » Astro Forum » STEREO Spacecraft Swing Past Moon, Preparing for 3-D Solar S
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 Posted: Tue Jan 23, 2007 6:27 pm |
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The Johns Hopkins University Applied Physics Laboratory
Office of Communications and Public Affairs
Media Contacts: Kristi Marren (JHU/APL)
(240) 228-6268 / Kristi.Marren@jhuapl.edu
Rani Chohan Gran (NASA Goddard Space Flight Center)
(301) 286-2483 / Rani.D.Chohan@nasa.gov
January 23, 2007
FOR IMMEDIATE RELEASE
Photos and the electronic version of this release are at
http://www.jhuapl.edu/newscenter/pressreleases/2007/070123.asp
TWIN APL-BUILT SPACECRAFT SWING PAST MOON, PREPARING FOR 3-D SOLAR
STUDIES
NASA's twin STEREO (Solar TErrestrial RElations Observatory)
spacecraft,
built and operated by the Johns Hopkins University Applied Physics
Laboratory (APL), in Laurel, Md., completed a series of complex
maneuvers
yesterday to position the spacecraft in their mission orbits. The
spacecraft will be in position to produce the first 3-D images of the
sun
by April.
Spacecraft trajectories and lunar swingby maneuvers were created by
mission
design engineers at APL. "STEREO is the first mission to use the moon's
gravity to redirect multiple spacecraft, launched aboard a single
rocket,
to their respective orbits," says Ron Denissen, APL STEREO project
manager.
During the initial weeks following launch, mission operations personnel
at
APL guided both spacecraft through a series of four highly elliptical
phasing orbits around Earth to position them for their lunar
gravitational
assists that propelled them into their respective mission orbits.
On Dec. 15, 2006, STEREO's "A" observatory flew past the moon at a
distance
of approximately 4,550 miles (7,340 kilometers) above its surface,
using
lunar gravity to redirect the spacecraft away from Earth and into its
orbit
"ahead" of Earth.
The "B" observatory passed approximately 7,300 miles (11,776
kilometers)
above the lunar surface where gravity is slightly weaker. Although the
"B"
observatory's orbit was slightly boosted, the spacecraft didn't undergo
its
full lunar gravitational assist until January 21 when it re-encountered
the
moon. The spacecraft then came within approximately 5,468 miles (8,818
kilometers) of the surface, swinging past the lunar body in the
opposite
direction of the "A" spacecraft and into an orbit "behind" Earth.
The two observatories will orbit the sun from this perspective,
separating
from each other by approximately 45 degrees per year. Just as the
slight
offset between your eyes provides you with depth perception, this
mirror-image-like positioning of the spacecraft will allow them to take
3-D
images and particle measurements of the sun.
First Images
During post-launch instrument checkouts, scientists got a close-up view
of
some intense solar activity from our nearest star, the sun, when the
"A"
observatory sent back its first images in early December.
When the cover to the "A" observatory's SECCHI Extreme Ultraviolet
Imager
telescope was removed on Dec. 4, 2006, it captured images of a very
powerful active region on the sun known as AR903 that produced a series
of
intense flares last month. SECCHI (Sun-Earth Connection Coronal and
Heliospheric Investigation), built by the Naval Research Laboratory
(NRL)
in Washington, D.C., is the imaging instrument suite aboard both
observatories.
A few days later during an unusually active solar period, the "A"
observatory captured images of a coronal mass ejection with one of
SECCHI's
two white-light coronagraphs.
Coronal mass ejections are giant clouds of plasma shot into space from
the
sun's atmosphere. One of the largest explosions in the solar system,
they
can equal the force of a billion megaton nuclear bombs. When they
collide
with Earth at speeds approaching one million mph, CMEs can produce
spectacular auroras and trigger severe magnetic storms. The energetic
particles associated with these storms can cause electrical power
outages,
disrupt and/or damage communications satellites, and are often
hazardous to
astronauts.
Each STEREO observatory is carrying more than a dozen instruments per
observatory. APL designed and built the spacecraft platform housing the
instruments. When combined with data from observatories on the ground
or in
space, STEREO's data will allow scientists to track the buildup and
liftoff
of magnetic energy from the sun and the trajectory of Earth-bound
coronal
mass ejections in 3-D.
STEREO's instruments were built by numerous organizations worldwide
with a
principal investigator, or PI, leading each instrument team. The
instruments and PIs are as follows: SECCHI - Russell Howard, NRL; In
situ
Measurements of PArticles and CME Transients (IMPACT) - Janet Luhmann,
University of California, Berkeley; PLAsma and SupraThermal Ion
Composition
(PLASTIC) - Antoinette Galvin, University of New Hampshire; and
STEREO/WAVES (S/WAVES) - Jean-Louis Bougeret, Paris Observatory,
Meudon.
STEREO is the third mission in NASA's Solar Terrestrial Probes Program.
STEREO is sponsored by NASA's Science Mission Directorate, Washington,
D.C.
NASA Goddard's Solar Terrestrial Probes Program Office, in Greenbelt,
Md.,
manages the mission, instruments and science center. APL designed and
built
the spacecraft and is operating them for NASA during the mission.
For more information about STEREO or to download additional images,
visit
stereo.jhuapl.edu or http://stereo.gsfc.nasa.gov/gallery/gallery.shtml
###
The Applied Physics Laboratory (APL) is a not-for-profit laboratory and
division of the Johns Hopkins University. APL conducts research and
development primarily for national security and for nondefense projects
of
national and global significance. APL is located midway between
Baltimore
and Washington, D.C., in Laurel, Md. |
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