PASADENA, Calif. -- NASA's Nuclear Spectroscopic Telescope Array, or
NuSTAR, has successfully deployed its lengthy mast, giving it the
ability to see the highest energy X-rays in our universe. The mission is
one step closer to beginning its hunt for black holes hiding in our
Milky Way and other galaxies.
"It's a real pleasure to know that the mast, an accomplished feat of
engineering, is now in its final position," said Yunjin Kim, the NuSTAR
project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Kim was also the project manager for the Shuttle Radar Topography
Mission, which flew a similar mast on the Space Shuttle Endeavor in 2000
and made topographic maps of Earth.
NuSTAR's mast is one of several innovations allowing the telescope to
take crisp images of high-energy X-rays for the first time. It separates
the telescope mirrors from the detectors, providing the distance needed
to focus the X-rays. Built by ATK Aerospace Systems in Goleta, Calif.,
this is the first deployable mast ever used on a space telescope.
On June 21 at 10:43 a.m. PDT (1:43 p.m. EDT), nine days after launch,
engineers at NuSTAR's mission control at UC Berkeley in California sent a
signal to the spacecraft to start extending the 33-foot (10-meter)
mast, a stable, rigid structure consisting of 56 cube-shaped units.
Driven by a motor, the mast steadily inched out of a canister as each
cube was assembled one by one. The process took about 26 minutes.
Engineers and astronomers cheered seconds after they received word from
the spacecraft that the mast was fully deployed and secure.
The NuSTAR team will now begin to verify the pointing and motion
capabilities of the satellite, and fine-tune the alignment of the mast.
In about five days, the team will instruct NuSTAR to take its "first
light" pictures, which are used to calibrate the telescope.
Why did NuSTAR need such a long, arm-like structure? The answer has to
do with the fact that X-rays behave differently than the visible light
we see with our eyes. Sunlight easily reflects off surfaces, giving us
the ability to see the world around us in color. X-rays, on the other
hand, are not readily reflected: they either travel right through
surfaces, as is the case with skin during medical X-rays, or they tend
to be absorbed, by substances like your bone, for example. To focus
X-rays onto the detectors at the back of a telescope, the light must hit
mirrors at nearly parallel angles; if they were to hit head-on, they
would be absorbed instead of reflected.
On NuSTAR, this is accomplished with two barrels of nested mirrors, each
containing 133 shells, which reflect the X-rays to the back of the
telescope. Because the reflecting angle is so shallow, the distance
between the mirrors and the detectors is long. This is called the focal
length, and it is maintained by NuSTAR's mast.
The fully extended mast is too large to launch in the lower-cost rockets
required for relatively inexpensive Small Explorer class missions like
NuSTAR. Instead NuSTAR launched on its Orbital Science Corporation's
Pegasus rocket tucked inside a small canister. This rocket isn't as
expensive as its bigger cousins because it launches from the air, with
the help of a carrier plane, the L-1011 "Stargazer," also from Orbital.
NuSTAR is a Small Explorer mission led by the California Institute of
Technology in Pasadena and managed by JPL for NASA's Science Mission
Directorate in Washington. The spacecraft was built by Orbital Sciences
Corporation, Dulles, Va. Its instrument was built by a consortium
including Caltech; JPL; the University of California, Berkeley; Columbia
University, New York; NASA's Goddard Space Flight Center, Greenbelt,
Md.; the Danish Technical University in Denmark; Lawrence Livermore
National Laboratory, Livermore, Calif.; and ATK Aerospace Systems,
Goleta, Calif. NuSTAR will be operated by UC Berkeley, with the Italian
Space Agency providing its equatorial ground station located at Malindi,
Kenya. The mission's outreach program is based at Sonoma State
University, Rohnert Park, Calif. NASA's Explorer Program is managed by
Goddard. JPL is managed by Caltech for NASA.
Image credit: NASA/JPL-Caltech
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