Tower Extension Test a Success for NASA's James Webb Space Telescope

To test the James Webb Space Telescope's readiness for
its journey in space, technicians successfully commanded
it to deploy and extend a critical part of the observatory
known as the Deployable Tower Assembly.
The primary purpose of the deployable tower is to create a
large gap between the upper part of the observatory that
houses its iconic gold mirrors and scientific instruments,
and the lower section known as the spacecraft bus which
holds its comparatively warm electronics and propulsion
systems. By creating a space between the two, it allows
for Webb's active and passive cooling systems to bring its
mirrors and sensors down to staggeringly cold
temperatures required to perform optimal science.
Webb was designed to look for faint traces of infrared
light, which is essentially heat energy. To detect the
extremely faint heat signals of astronomical objects that
are incredibly far away, the telescope itself has to be very
cold and stable.
During the test, the tower was slowly extended 48 inches
(1.2 meters) upward over the course of several hours, in
the same maneuver it will perform once in space.
Simulating the zero-gravity environment Webb will operate
in, engineers employed an innovative series of pulleys,
cOunterbalances and a special crane called a
gravity-negation system that perfectly offloaded all of the
effects of Earth's gravity on the observatory. Now that
Webb is fully assembled, the difficulty of testing andproperly simulating a zero-gravity environment has
increased significantly.
"The Deployable Tower Assembly worked beautifully
during the test" said Alphonso Stewart the Webb
deployment systems lead for NASA's Goddard Space
Flight Center in Greenbelt, Maryland. "It performed exactly
as predicted, and from our expectations from previous
tests before the full observatory was assembled. This was
the first time that this part of Webb was tested in its
flight-like configuration to the highest level of fidelity we
possibly could. This test provides the opportunity to
assess all interfaces and interactions between the
instrument and bus sections of the observatory."
In addition to helping the observatory cool down, the
Deployable Tower Assembly is also a big part of how
Webb is able to pack down into a smaller size to fit inside
an Ariane 5 rocket for launch. Webb is the largest space
science observatory ever built, but to fit a telescope that
big into a rocket, engineers had to design it to fold down
into a much smaller configuration. Webb's Deployable
Tower Assembly helps Webb to just barely fit inside a
17.8-foot (5.4-meter) payload fairing. Once in space, the
tower will extend to give the rest of Webb's deployable
parts, such as the sunshield and mirrors, the necessary
amount of room needed to unpack and unfold into a fully
functional infrared space observatory.
For more information about Webb, visit www.nasa.gov/
webb
Music credit: Universal Production Music, "Timelapse
Clouds" by Blythe Joustra