Engineers
have successfully tested the mirror-controlling "brain" of the James
Webb Space Telescope (JWST), which is expected to rival imagery taken by the
Hubble Space Telescope.
The
software, known as Wavefront Sensing and Control (WFSC), will allow the
Webb telescope to adjust its 18 hexagonal mirrors.
"It's
critical that all 18 mirror segments be aligned in position so that they act as
one smooth surface," said Bill Hayden, a systems engineer at NASA's
Goddard Space Flight Center (GSFC) in Greenbelt, Md. "This will allow
scientists to clearly focus on very dim objects that we can't see now."
JWST is
slated for launch in 2013.
Hubble
rival
With a
combined mirror surface of 269 square feet (25 square meters), the Webb
telescope will have nearly six times the light-gathering ability of Hubble
Telescope, which has one giant 46-square-foot (4.3-square-meter) mirror.
Astronomers expect such sensitivity to allow them to see the first stars and
galaxies of the universe as well as young planetary systems.
The Webb
telescope will launch in a folded-up configuration, later unfurling its
lightweight beryllium mirrors in orbit one million miles (1.6 million
kilometers) from Earth. Unadjusted, however, the Webb telescope's mirrors would
produce blurry images like Hubble did when it first peered into the cosmos.
David L.
Taylor, president and chief executive officer of Ball Aerospace &
Technologies Corp., said WFSC software that will prevent the problem is based
on the same code used to fix the Hubble
telescope's imperfections.
"This
major technological accomplishment, which built on the legacy of software algorithms
used to fix the Hubble Space Telescope and align the Keck telescope," said
John Mather, the Webb telescope's senior project scientist at GSFC.
Mini-Webb
To test the
WFSC software, engineers created a one-sixth scale model of the Webb telescope
model in the laboratory. Once in space, the real 6.2-ton (13,700-pound)
telescope will snap a picture of the cosmos, run the software correlating the
18 different light sources (its mirrors) and then correct them using tiny
motors.
In the
quarterly newsletter issued by the Webb telescope's scientists, Hayden said the
testing isn't fully complete, but should go forward without a hitch.
"The
tests started in mid-October and will finish by early December," Hayden
said, adding that recent results suggest final testing "will be very
successful."
Webb
telescope scientists presented their mirror-adjusting work on Aug. 26 at the
Society for Photo-Optical Instrumentation Engineers meeting in San Diego, Calif.
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