Thermal Core Testing Complete, Data To Be Analyzed
Northrop Grumman Corporation has completed testing on a model of
the "core" section of NASA's James Webb Space Telescope (JWST) to
validate the observatory's sophisticated thermal modeling and
design. The company is leading an industrial team in the design and
development of the Webb Telescope for NASA Goddard Space Flight
Center.
"This test represents JWST's
first large-scale thermal performance and demonstration test after
a decade in development," said Martin Mohan, JWST program manager
for Northrop Grumman's Aerospace Systems sector. "At this early
juncture, it appears that our test objectives were achieved. The
team gathered a tremendous amount of data that we'll review over
the coming months to assess the implications for the current
observatory design."
The Webb Telescope's unique design features a sunshield that
separates the observatory into a warm sun-facing side, and a cold
side facing away from the sun. The warm side will be subjected to
nearly 100,000 thermal Watts of heat from the sun, while the cold,
anti-sun side, where the optical telescope element and science
instrument module are located, will be cooled passively to as low
as -414 degrees Fahrenheit (25 K, or slightly above absolute zero).
These elements come together at the observatory's central, or core,
region.
The core model built by Northrop Grumman is a thermal facsimile
of the Webb Telescope's central region and stands about two stories
tall, or 17.5 feet, and 17 feet wide. It consists of the top
portion of the spacecraft bus, deployable tower, a truncated but
fully tensioned five-layer sunshield, optical telescope element
backplane support frame, integrated science instrument module
(ISIM) compartment, cable trays, thermal management systems, and
ISIM electronics compartment.
Testing was conducted in Northrop Grumman's largest thermal
vacuum chamber at the company's space systems manufacturing
facilities over nearly six weeks. To simulate the extreme cold JWST
will experience in space, Northrop Grumman upgraded the chamber
with a gaseous helium-refrigerated shroud and precisely monitored
the test with 550 individual temperature sensors. The chamber
provided a background operating temperature as low as -435 degrees
F (13K).
The telescope operates at temperatures approaching absolute zero
to best see the near- and mid-infrared light coming from the very
first stars and galaxies.
"I can't overstate how much of a milestone this test represents
and the remarkable achievement it is just getting this large test
article to flight-like temperatures and gathering the needed data,"
said Keith Parrish, NASA Goddard Space Flight Center, JWST Deputy
Observatory/Sunshield manager. "The fact that it went as smoothly
and with as little fanfare speaks volumes to the planning, build
quality, facility operations, and foresight of the entire team.
This test expands the joint NGAS/NASA institutional knowledge for
large cryogenic testing and will contribute to the even more
complex flight article testing later in the program."