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August
10, 2007: The road to the Marshall Space Flight Center
is mighty dark at 3:30 a.m. There are no streetlights or buildings
along this long stretch of rural highway. Only the gleaming
eyes of raccoons and skunks peer out from among thick-set
pines. Once you get to the Marshall complex, the buildings
are all dark too, except for one -- the X-Ray Calibration
Facility (XRCF). Here, the lights are on all night and someone
is home.
Barry
Hale (lead technician) and Jay Carpenter (facility engineer)
are working the night shift. At least two people man this
facility every night, monitoring screens on a large panel
in the control room. Twelve people have alternated shifts
24/7 since late May.
 Why
have all these people become "all-nighters?" The
success of NASA's next great space telescope depends upon
it: "We're testing the James Webb Space Telescope,"
explains XRCF team leader Jeff Kegley.
Right:
An artist's concept of the James Webb Space Telescope. [Larger
image] [JWST
home]
Scheduled
for launch in 2013, the Webb telescope is widely regarded
as the premier observatory of the next decade. It is an infrared
telescope, which means it senses the heat of stars and galaxies
millions and even billions of light years away. To pick up
those incredibly faint signs of warmth, the telescope itself
must be kept extremely cold—and that is why everyone is staring
at screens.
The
Webb telescope will operate in space at a temperature of -238
deg Celsius (-396 deg Fahrenheit). Such extreme cold may cause
the telescope's structures and mirrors to change shape. Before
that happens, the telescope is being tested at the XRCF, piece
by piece, inside a vacuum chamber that simulates the hyper-cold
of space. Results reveal any distortion that happens to the
components so changes can be made if needed.
But
there's a lot more to the night shift than staring at control
panel test data. Like most night crews, Hale and Carpenter
make "rounds." These rounds include going outdoors
to check the "nitrogen farm," where huge white tanks
of liquid nitrogen loom in the darkness like dairy cattle
in a pasture. The nitrogen is used to cool the vacuum chamber
where components are tested, and the men check for leaks each
night.
Hale
and Carpenter have also caught glimpses of some real animals
out on the farm. One night, Hale had a close encounter of
the UNkind with a skunk – giving new meaning to the term "skunk
works."
Above:
Scenes from the XRCF, from left to right: (1)
By day, the road leading to the test facility; (2)
all-nighter Dr. Joseph Geary monitors test data; (3)
The portal to the test chamber; (4)
Barry Hale at the XRCF control panel; (5)
Jay Carpenter tours the nitrogen farm at dawn. Click on the
parenthetical numbers to view larger images.
By
making these "dangerous" field surveillance rounds
and watching the control room screens, the night crew ensures
that all equipment pressures, flow rates, temperatures, and
valve positions stay in proper range for the tests. They also
manipulate helium refrigeration systems, vacuum chamber pressure,
and liquid nitrogen zones for the vacuum chamber to keep the
test article on a particular test plan profile.
"Tonight's
test article is a section of the ISIM Breadbox," says
Carpenter. "That's our nickname for the Integrated Science
Instrument Module support structure, which holds the telescope's
four main science instruments." (For instrument wonks,
their names are Mid-Infrared Instrument, Near-Infrared Camera,
Near-Infrared Spectrograph, and Fine Guidance Sensor.)
Right:
The cryogenic vacuum chamber at the XRCF where components
of the James Webb Telescope are being tested. [Larger
image]
 As
the Breadbox in the test chamber endures the transition from
room temperature down to -233 deg Celsius (-387 deg Fahrenheit),
an Electronic Speckle Pattern Interferometer optically measures
the structural distortion. No, this is not a rare salamander,
but it is a rare instrument. "This is one of only two
instantaneous phase-shift speckled interferometers in the
world," says Joseph Geary of the University of Alabama-Huntsville
who, by the way, is also working night shift on this particular
night. The interferometer is being used to detect thermal
distortions of the Breadbox as small as a few nanometers (billionths
of a meter).
In
a few days, after the Breadbox testing draws to a close, the
crew will reconfigure the facility for mirror segment verification
tests. The Webb telescope consists of 18 individual mirror
segments that will ultimately form a 6.5-meter mirror assembly.
In the spring, engineers will begin testing the optical quality
of each individual mirror segment. The 24/7 testing will continue
through 2010. That's a lot of testing, a lot of night shifts,
and a lot of skunks.
Carpenter
comments that he doesn't really mind working nights, but says
"It's a little hard on my family to be quiet during the
day when I have to sleep. My granddaughter wants to play,
but she isn't allowed to knock on my door. That's a little
hard for me, too."
Kegley
says he likes to work the night shift occasionally because
it’s a good chance to catch up on work. "You don't get
many calls or e-mails to interrupt you at 3 o'clock in the
morning."
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The
Goddard Space Flight Center manages development of the JWST
and provides the ISIM. Marshall Space Flight Center's Science
and Mission Systems Office manages the JWST components testing
at the XRCF.
Author: Dauna Coulter | Editor:
Dr. Tony Phillips | Credit: Science@NASA
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