X-ray and Cryogenic Facility

National Aeronautics and Space Administration
X-ray and Cryogenic Facility
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The X-ray and Cryogenic Facility at NASA’s Marshall
General Facility Description
Space Flight Center in Huntsvil e, Ala., is a unique,
The X-ray and Cryogenic Facility consists of a
f
a
world class optical, cryogenic and X-ray test
1,700-foot-long X-ray guide tube, a horizontal
facility — in fact, the world’s largest X-ray telescope
cylindrical vacuum chamber cal ed the Instrument
test facility. Built in 1975 to perform ground tests
Chamber, and two clean rooms.
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and calibration of the High Energy Astronomy
Observatory-2, the X-ray Calibration Facility, as it
For instruments headed to space, the word “clean”
was first known, was extensively modified in 1989–
takes on a new emphasis. Cal ing a room “clean” at
1991 to perform ful -scale calibration tests for the
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the X-ray and Cryogenic Facility means that room
Chandra X-ray Observatory. Chandra is the most
has a low level of environmental pol utants like dust,
sophisticated X-ray observatory built to date — an
airborne microbes, aerosol particles and chemical
instrument that is providing unprecedented views
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vapors. A clean room’s contamination level,
of the universe. In 1999, the X-ray facility was
indicated by the room’s classification, is control ed
upgraded to perform cryogenic, or extremely low
to a specified number of particles per cubic foot at
temperature, testing without compromising X-ray
a specified particle size. For example, class 2000
N
calibration test capability and was renamed the
means the room’s contamination level is less than
X-ray and Cryogenic Facility.
2,000 particles ½ micron and larger in diameter per
cubic foot.
Today, the X-ray and Cryogenic Facility supports
the James Webb Space Telescope program.
The X-ray and Cryogenic Facility’s instrument
Scheduled for launch in 2013, the Webb telescope
chamber opens into a 5,400-square-foot class
is an infrared telescope, meaning it senses the
2000 clean room in which the test article is
heat of stars and galaxies which are mil ions and
prepared for thermal vacuum testing and placed
even bil ions of light years away. The telescope
onto a test stand. Another clean room, this one a
itself must be kept extremely cold in order to pick
2,000-square-foot and class 10000 facility, serves
up incredibly faint signs of warmth. It will operate in
space at a temperature of minus 396 F (35 Kelvin).
To prepare the Webb structures and mirrors to meet
the extreme temperatures of space, engineers will
careful y examine telescope components inside a
vacuum chamber that simulates the hyper-cold of
space, chil ing the hardware from room temperature
down to frigid minus 414 F. Results will reveal
any distortion that happens to the components
so changes can be made if needed. Testing and
calibration of instruments prior to launch can help
reduce unexpected and costly problems before
they happen in space.
JWST Mirror Simulators in Clean Room

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as an airlock for the larger clean room. This clean room has
Cryogenic and Cryogenic Optical Test Capability
direct access to the X-ray and Cryogenic Facility unloading
The X-ray and Cryogenic Facility is equipped with a helium-
dock. The clean rooms and unloading area are outfitted with
cooled enclosure that provides a test environment from
a lift platform, forklifts and overhead cranes, and staffed with
ambient to minus 414 F (25 Kelvin). Two helium refrigerators
highly skil ed personnel for handling large optics and other
cool the enclosure by expansion of pre-cooled helium gas.
test hardware.
The outside of the enclosure is insulated like the wal s of
a home refrigerator, but with 30 layers of insulation. The
The extremely clean instrument chamber test vacuum —
combination of the vacuum environment and insulated wal s
20 feet in diameter and 60 feet long — has several electrical
al ows the enclosure to reach a temperature of less than minus
and fluid interfaces needed for running tests. Cryogenic and
414 F (25 Kelvin). The inside of the enclosure has provisions to
vacuum pumps provide typical test pressures of less than
hold a test article that is vibration isolated from the enclosure
10–6 Torr. Torr is a unit of pressure, and 10–6 Torr equals
wal s and the chamber. The facility has a variety of enclosures
about one-bil ionth atmospheric pressure.
that can be connected to the refrigerators in several shapes
and sizes. Temperature can be control ed in 0.1 Kelvin
A sophisticated control system monitors and records more
increments from 300 to 15 Kelvin, and programmed profiles
than 2,000 channels of temperatures, pressures and other
are possible.
data. The instrument chamber’s main test volume can be
thermal y control ed in an operating range of minus 180 F
The X-ray and Cryogenic Facility can test mirrors up to
to 180 F.
13.12 feet in diameter. The facility has two interferometers
— instruments for optical y measuring structural distortions
Two remotely operated motion tables are available for
that occur during cryogenic testing of telescope mirrors.
mounting test articles in the vacuum environment. Both
Both interferometer systems offer fast, quantitative surface
the Five Axis Mount typical y used for X-ray testing, and
figure measurement that is relatively insensitive to the effects
the Mirror Table used for cryogenic testing, can precisely
of vibration. These instruments can detect thermal distortions
position a test article at any angle desired.
as small as a few nanometers (bil ionths of a meter). More
than 30 cryogenic test operations have been completed since
X-ray Test Capability
1999 — most in support of the James Webb Space Telescope.
The X-ray and Cryogenic Facility’s X-ray source system,
used to simulate emissions from distant celestial objects,
Additional Capabilities
is located on the end of the X-ray guide tube 1,700 feet from
In addition to the large vacuum chamber, the facility has a
the instrument chamber. The source system produces a
smal er, more cost-effective cryogenic and cryogenic optical
57.5-inch X-ray beam at the chamber entrance. The X-ray
testing chamber. The helium-cooled test volume in the small
detectors monitor the X-ray beam and provide feedback
chamber is a horizontal cylinder 40 inches in diameter and
to the X-ray generator. An adjustable optical mount on a
88 inches deep. This chamber achieves test pressures and
moveable stage at the instrument chamber entrance traces
temperatures comparable to those of the large chamber, but
incoming X-ray beams. Detectors also are mounted on
in about one-tenth the time. It uses control and data acquisi-
motion stages, al owing them to be moved in or out of focus
tion systems similar to those of the larger chamber and uses
and/or to scan across the X-ray image. An array of pinholes
the same interferometer systems. More than 25 cryogenic test
and slits can be remotely inserted between the detectors
operations have been completed in the small chamber since
and the mirror under test to redirect X-ray beams as needed.
it was commissioned in 2001.
More than 20 X-ray mirror, instrument and telescope
calibrations have been completed since 1991, including
Chandra, five Solar X-ray Imagers for a series of National
Oceanic and Atmospheric Administration meteorological
satel ites, and Hinode’s X-ray Telescope — a project that is
exploring the magnetic fields of the sun.
National Aeronautics and Space Administration
George C. Marshall Space Flight Center
Huntsville, AL 35812
www.nasa.gov/marshall
Cryogenic Optical Test Configuration
www.nasa.gov
FS–2009–01–11–MSFC
NASA Facts
8–405855

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