The first spacecraft designed to capture 3-D "stereo"
views of the sun and solar wind were shipped last week from
the Applied Physics
Laboratory, where they were designed and built, to NASA
Goddard Space Flight Center in Greenbelt, Md., for their
next round of pre-launch tests.
The two nearly identical observatories, called STEREO
for Solar TErrestrial RElations Observatory, were recently
tested in APL's vibration lab, where engineers used a large
shake table to check their structural integrity. These
tests simulate the ride into space the spacecraft will
encounter aboard a Delta II launch vehicle from Cape
Canaveral Air Force Station, Fla., where they're scheduled
for a spring launch.
"Delivery of the twin observatories to NASA is a
program milestone," Ed Reynolds, APL STEREO project
manager, said. "Building two nearly identical spacecraft
simultaneously was a technical and scheduling challenge,
but one our team welcomed and tackled with extreme
professionalism and dedication. With the design,
construction and now delivery of the observatories to NASA
Goddard, we're very excited to help NASA get one step
closer to launch and capturing the first-ever 3-D images of
the sun."
During the next three months at Goddard Space Flight
Center, the twin observatories will undergo additional
pre-launch checks, including spin tests to check the
spacecraft's balance and alignment, thermal vacuum tests to
duplicate the extreme temperature and airless conditions of
space, and acoustic tests that simulate the noise-induced
vibrations of launch. The mission team plans to transport
the spacecraft to Florida in March for final launch
preparations.
During the two-year STEREO mission, the space-based
observatories will explore the origin, evolution and
interplanetary consequences of coronal mass ejections.
These powerful solar eruptions are a major source of the
magnetic disruptions on Earth and a key component of space
weather, which can greatly affect satellite operations,
communications, power systems and the lives of humans in
space.
To obtain "stereo" views of the sun, the observatories
must be placed into different orbits where they're offset
from each other and the Earth. One observatory will be
placed ahead of Earth in its orbit around the sun and the
other behind. Just as the slight offset between your eyes
provides you with depth perception, this placement will
allow the STEREO observatories to obtain 3-D images and
particle measurements of the sun.
"This is the first time lunar swingbys will be used to
place multiple spacecraft into their respective orbits,"
APL's Andy Driesman, STEREO system engineer, said. "Mission
designers at APL will use the moon's gravity to redirect
the observatories to their appropriate orbits around the
sun. This innovative mission design allows the use of a
single launch vehicle."
After launch, the observatories will fly in an orbit
from a point close to Earth to one that extends just beyond
the moon. Approximately two months later, mission
operations personnel at APL will synchronize spacecraft
orbits, directing one observatory to its position trailing
Earth in its orbit. Approximately one month later, the
second observatory will be redirected to its position ahead
of Earth.
STEREO is the third mission in NASA's Solar
Terrestrial Probes Program and is sponsored by NASA's
Science Mission Directorate, Washington, D.C. NASA GSFC's
Solar Terrestrial Probes Program Office manages the
mission, instruments and science center. APL designed,
built and will operate the twin observatories for NASA
during the mission.
For more information about the mission, go to
stereo.jhuapl.edu.
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