Abstract :
Over the last decade, there have been a number of innovations
that have made possible the largest and most powerful telescope of its
time: the James Webb Space Telescope (JWST). Scheduled to launch in
2018, JWST will provide insight into what the oldest, most distant
galaxies look like. When engineers build a first-of-its-kind instrument
like the JWST, they often must make new tools to construct the new
technology. Throughout the decades of planning, development, and
construction of the JWST, NASA has worked with numerous partners to spur
innovations that have enabled the telescope s creation. Though the JWST
s launch date is still several years away, a number of these
innovations are spinning off to provide benefits here on Earth. One of
these spinoffs has emerged from the extensive testing the JWST must
undergo to ensure it will function in the extreme environment of space.
In order to test the JWST instruments in conditions that closely
resemble those in space, NASA uses a cryogenic vacuum chamber. By
dropping the temperatures down to -400 F and employing powerful pumps to
remove air from the chamber, engineers can test whether the JWST
instruments will function once the spacecraft leaves Earth.
Traditionally, a phase-shifting interferometer is used to measure optics
like the JWST s mirrors to verify their precise shape, down to tens of
nanometers, during manufacturing. However, the large size of the
mirrors, coupled with vibration induced by the cryo-pumps, prohibits the
use of traditional phase-shifting interferometers to measure the
mirrors within the chamber environment. Because the JWST will be located
in deep space, far from any possible manned service mission, it was
essential to find a robust solution to guarantee the performance of the
mirrors.
Source : NASA
Document Url : http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130009019_2013008668.pdf
No comments:
Post a Comment