WEBVTT

00:00:00.000 --> 00:00:01.488 align:middle line:90%
[MUSIC PLAYING]

00:00:01.488 --> 00:00:13.400 align:middle line:90%


00:00:13.400 --> 00:00:15.170 align:middle line:84%
The James Webb
Space Telescope is

00:00:15.170 --> 00:00:17.600 align:middle line:84%
what's known as a
reflector telescope,

00:00:17.600 --> 00:00:20.720 align:middle line:84%
two mirrors-- one primary
and one secondary-- used

00:00:20.720 --> 00:00:23.930 align:middle line:84%
to collect and focus light
coming from faraway objects

00:00:23.930 --> 00:00:24.980 align:middle line:90%
they're looking at.

00:00:24.980 --> 00:00:27.260 align:middle line:84%
The primary mirror
on James Webb is

00:00:27.260 --> 00:00:31.040 align:middle line:84%
so huge it needs to be assembled
from 18 separate mirrors.

00:00:31.040 --> 00:00:32.900 align:middle line:84%
To find out more
about these mirrors

00:00:32.900 --> 00:00:35.870 align:middle line:84%
and how NASA's making sure they
work as well in space as they

00:00:35.870 --> 00:00:38.510 align:middle line:84%
do on the ground, we've come
to the Marshall Space Flight

00:00:38.510 --> 00:00:40.880 align:middle line:90%
Center in Huntsville, Alabama.

00:00:40.880 --> 00:00:42.050 align:middle line:90%
We're here with Jeff Kegley.

00:00:42.050 --> 00:00:45.278 align:middle line:84%
And he's the director of the
X-ray and Cryogenic Facility

00:00:45.278 --> 00:00:46.820 align:middle line:84%
here at Marshall
Space Flight Center.

00:00:46.820 --> 00:00:49.100 align:middle line:84%
So, Jeff, tell us a little
bit about where we are

00:00:49.100 --> 00:00:50.780 align:middle line:90%
and what are you about to see?

00:00:50.780 --> 00:00:55.070 align:middle line:84%
Mary, we are in the entry
area for our large clean room.

00:00:55.070 --> 00:00:57.560 align:middle line:84%
These James Webb Space
Telescope mirrors

00:00:57.560 --> 00:00:59.420 align:middle line:84%
have to stay in a very
clean environment.

00:00:59.420 --> 00:01:01.170 align:middle line:84%
And we have that type
of environment here.

00:01:01.170 --> 00:01:03.003 align:middle line:84%
So we're going to see
if we can get a better

00:01:03.003 --> 00:01:04.010 align:middle line:90%
look at those mirrors.

00:01:04.010 --> 00:01:06.500 align:middle line:84%
And to do that, we're
going to have to get

00:01:06.500 --> 00:01:09.035 align:middle line:84%
dressed up a little bit so
that only our eyes are showing.

00:01:09.035 --> 00:01:28.130 align:middle line:90%


00:01:28.130 --> 00:01:31.400 align:middle line:84%
We're just about to pull
the entire test and assembly

00:01:31.400 --> 00:01:35.360 align:middle line:84%
into the vacuum chamber with
the three James Webb mirrors

00:01:35.360 --> 00:01:36.870 align:middle line:90%
aboard.

00:01:36.870 --> 00:01:38.640 align:middle line:84%
I notice there's
just three mirrors.

00:01:38.640 --> 00:01:39.140 align:middle line:90%
Why is that?

00:01:39.140 --> 00:01:41.480 align:middle line:84%
I think James Webb
has 18, right?

00:01:41.480 --> 00:01:44.347 align:middle line:84%
Right, the James Webb Telescope
is made up of 18 mirrors.

00:01:44.347 --> 00:01:46.430 align:middle line:84%
We're going to have each
one of those mirrors come

00:01:46.430 --> 00:01:47.960 align:middle line:90%
through here twice.

00:01:47.960 --> 00:01:49.610 align:middle line:84%
The first time
through, we actually

00:01:49.610 --> 00:01:52.790 align:middle line:84%
measure the deformation as
a function of temperature

00:01:52.790 --> 00:01:56.720 align:middle line:84%
as we transition down to
minus 400 degrees Fahrenheit.

00:01:56.720 --> 00:01:58.430 align:middle line:84%
The second time
through, we verify

00:01:58.430 --> 00:02:00.470 align:middle line:84%
that the mirrors actually
perform correctly

00:02:00.470 --> 00:02:01.662 align:middle line:90%
at that temperature.

00:02:01.662 --> 00:02:03.620 align:middle line:84%
And you said it's about
to go into the chamber.

00:02:03.620 --> 00:02:05.690 align:middle line:84%
Can we go inside the chamber
just to see what it's like

00:02:05.690 --> 00:02:07.732 align:middle line:84%
and maybe tell us a little
bit about the chamber?

00:02:07.732 --> 00:02:09.860 align:middle line:84%
Yeah, we'll try to run in
there and see if we can

00:02:09.860 --> 00:02:11.435 align:middle line:90%
beat this transition inside.

00:02:11.435 --> 00:02:15.030 align:middle line:90%


00:02:15.030 --> 00:02:17.040 align:middle line:84%
The mirrors behind
us will be pulled in

00:02:17.040 --> 00:02:19.530 align:middle line:84%
and will actually reside
just up in front of us

00:02:19.530 --> 00:02:21.510 align:middle line:84%
here, inside the
chamber where they can

00:02:21.510 --> 00:02:23.580 align:middle line:90%
be cooled to minus 400 degrees.

00:02:23.580 --> 00:02:25.770 align:middle line:90%
Why a vacuum chamber?

00:02:25.770 --> 00:02:28.590 align:middle line:84%
Well, we have to simulate not
only the thermal environment

00:02:28.590 --> 00:02:30.930 align:middle line:84%
but also the vacuum
environment of space.

00:02:30.930 --> 00:02:33.900 align:middle line:84%
You pull these in and
what kind of things

00:02:33.900 --> 00:02:36.420 align:middle line:84%
are you looking
for in the mirror?

00:02:36.420 --> 00:02:38.550 align:middle line:84%
Well, the Ball Aerospace
team is actually

00:02:38.550 --> 00:02:39.875 align:middle line:90%
responsible for the testing.

00:02:39.875 --> 00:02:41.250 align:middle line:84%
And they will
actually be looking

00:02:41.250 --> 00:02:43.920 align:middle line:84%
at these mirrors
as they transition

00:02:43.920 --> 00:02:46.590 align:middle line:84%
to a cryogenic temperature
through a window

00:02:46.590 --> 00:02:48.630 align:middle line:84%
up in the front of
our vacuum chamber.

00:02:48.630 --> 00:02:50.520 align:middle line:84%
And they'll be looking
at these mirrors

00:02:50.520 --> 00:02:53.160 align:middle line:84%
with an instrument
called an interferometer.

00:02:53.160 --> 00:02:56.040 align:middle line:84%
And that's going to give
them a very detailed surface

00:02:56.040 --> 00:02:58.740 align:middle line:84%
map of what that
mirror looks like

00:02:58.740 --> 00:03:02.130 align:middle line:84%
and how it deforms as a
function of temperature.

00:03:02.130 --> 00:03:03.810 align:middle line:84%
And my last question
is, why is it

00:03:03.810 --> 00:03:06.930 align:middle line:84%
so important to be so
precise with these mirrors?

00:03:06.930 --> 00:03:08.850 align:middle line:84%
Well, the primary
mirror for a telescope

00:03:08.850 --> 00:03:11.730 align:middle line:84%
is the part of the telescope
that really matters.

00:03:11.730 --> 00:03:14.400 align:middle line:84%
It's gathering all the
light that ultimately

00:03:14.400 --> 00:03:16.440 align:middle line:90%
gets focused on the instrument.

00:03:16.440 --> 00:03:19.950 align:middle line:84%
And the larger and the
better the mirrors are,

00:03:19.950 --> 00:03:21.570 align:middle line:90%
the better the telescope is.

00:03:21.570 --> 00:03:30.320 align:middle line:90%


00:03:30.320 --> 00:03:32.120 align:middle line:84%
These mirrors will be
in the vacuum chamber

00:03:32.120 --> 00:03:35.000 align:middle line:84%
for about 15 weeks, going
through seven cycles

00:03:35.000 --> 00:03:37.340 align:middle line:84%
of temperature changes
from room temperature

00:03:37.340 --> 00:03:42.500 align:middle line:84%
to the cold extreme of space,
414 degrees below zero.

00:03:42.500 --> 00:03:45.440 align:middle line:84%
Thanks again for joining
us Behind the Webb.

00:03:45.440 --> 00:03:47.890 align:middle line:90%
[MUSIC PLAYING]

00:03:47.890 --> 00:03:58.000 align:middle line:90%