প্রকাশ: 13/01/2022
NASA on Wednesday embarked on a months-long, painstaking
process of bringing its newly launched James Webb Space Telescope into focus, a
task due for completion in time for the revolutionary eye in the sky to begin
peering into the cosmos by early summer.
Mission control engineers at NASA's Goddard Space Flight
Center in Greenbelt, Maryland, began by sending their initial commands to tiny
motors called actuators that slowly position and fine-tune the telescope's
principal mirror.
Consisting of 18 hexagonal segments of gold-plated beryllium
metal, the primary mirror measures 21 feet 4 inches (6.5 m) in diameter - a
much larger light-collecting surface than Webb's predecessor, the 30-year-old
Hubble Space Telescope.
The 18 segments, which had been folded together to fit
inside the cargo bay of the rocket that carried the telescope to space, were
unfurled with the rest of its structural components during a two-week period
following Webb's launch on Dec. 25.
Those segments must now be detached from fasteners that held
them in place for the launch and then moved forward half an inch from their
original configuration - a 10-day process - before they can be aligned to form
a single, unbroken, light-collecting surface.
The alignment will take an additional three months, Lee
Feinberg, the Webb optical telescope element manager at Goddard, told Reuters
by telephone.
Aligning the primary mirror segments to form one large
mirror means each segment "is aligned to one-five-thousandth the thickness
of a human hair", Feinberg said.
"All of this required us to invent things that had
never been done before," such as the actuators, which were built to move
incrementally at -400 Fahrenheit (-240 Celsius) in the vacuum of space, he
added.
The telescope's smaller, secondary mirror, designed to
direct light collected from the primary lens into Webb's camera and other
instruments, must also be aligned to operate as part of a cohesive optical
system.
If all goes as planned, the telescope should be ready to
capture its first science images in May, which would be processed over about
another month before they can be released to the public, Feinberg said.
The $9-billion telescope, described by NASA as the premier
space-science observatory of the next decade, will mainly view the cosmos in
the infrared spectrum, allowing it to gaze through clouds of gas and dust where
stars are being born. Hubble has operated primarily at optical and ultraviolet
wavelengths.
Webb is about 100 times more powerful than Hubble, enabling
it to observe objects at greater distances, thus farther back in time, than
Hubble or any other telescope.
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