Program Information

Series: NASA Connect
Program: The Measurement of All Things: Atmospheric Detectives
Segment Number: 3 (Watch entire program)
Duration: 00:04:12
Year Produced: 1999
Description:

NASA Connect Segment explains how scientist use LIDAR to help them measure aerosols in the atmosphere. It also describes active remote sensing.

NASA CONNECT™ is a series of Emmy®-award-winning, math-focused programs. Each program supports the national math, science, and technology standards and has three components that include (1) a 30-minute television broadcast; (2) a companion educator's guide; and (3) an online activity that further explores topics presented in the broadcast. These programs establish a connection between the math, science, and technology concepts taught in the classroom to those same concepts used everyday by NASA researchers.

For more information visit: http://connect.larc.nasa.gov/

Transcript

Here in our lab
at NASA Langley,
we use a technique
called active remote sensing.

Now, that means that we
carry our own light source.

We don't wait around for the Sun
to shine on the object.

What we do is, we use
short pulses of laser light
to probe the atmosphere.

This technique is called LIDAR.

LIDAR stands for
light detection and ranging.

A LIDAR uses short pulses
of laser light
to detect aerosols
in the atmosphere.

NASA Langley
is involved
in active remote sensing
from the ground and in the air.

At NASA Ames, in California,
LIDAR is flown
in the high-altitude
ER2 aircraft
to record atmospheric data.

And at NASA Dryden,
also in California,
a high-altitude, solar-powered,
unpiloted airplane
is being developed
that can stay aloft for weeks,
even months at a time, to make
atmospheric measurements.

So how does LIDAR work?

Well, first of all,
we open this trap door
and then align our LIDAR
under the open sky.

Then we shoot a pulsed laser
beam into the atmosphere.

Some of that laser beam
scatters off
the tiny aerosol particles
and scatters light
into this telescope.

The light is then captured by
this detector.

By precisely timing
the laser pulse
going out into the atmosphere
and the reflected light
coming back to the telescope,
scientists
can accurately measure
the location and number
of aerosols.

Now, remember,
this is active remote sensing,
much like that flash
on the camera.

Okay, I understand passive
and active remote sensing
and how LIDAR works.

But how do you measure
the distance from the ground
to the aerosols
in the atmosphere?

You can't use a meter stick.

Okay, let's say you wanted
to measure something far away
say, like aerosols in the sky.

You're right; you wouldn't
use a meter stick.

Scientists at NASA Langley
use mathematics.

A pulse of laser light
is shot from point A.

The beam travels from point A
to the aerosols at point B.

Then light reflects
off the aerosols
and bounces back to point A.

If you know how fast it takes
for a pulse of laser light
to travel
and you know a little math,
then you can calculate
how far away the aerosols are
in the atmosphere.

Check it out.

It takes a pulse of light
one nanosecond
to travel 1/3 of a meter.

What is a nanosecond?

A nanosecond is one billionth
of a second.

Basically...

[chalk squeaking]
It's a really small
amount of time.

Anyway, if a scientist
shoots a pulse of laser light
at the sky...
ting ting ting ting ting
and that beam reflects back...
ting ting ting ting ting
Say, in 6,000 nanoseconds,
the aerosols in the sky
are really...
3,000 nanoseconds away.

Why?

Because you have to divide
the total time by two
in order to find
the time one way.

Got it?

So if you multiply the time
one way--3,000 nanoseconds--
by the number of meters
in a nanosecond--1/3--
you get 1,000 meters.

If you know how to convert
meters to kilometers,
you can calculate
that the aerosols in the sky
are one kilometer away.

Well, that should
answer your question, Van.

But you know, in order
to get the whole picture,
we need to measure aerosols
from space.

Let me call a few colleagues
of mine at Hampton University
who are working
with NASA Langley,
Ball Aerospace,
and the French space agency
to get them
to explain to you
how we can measure
aerosols from space.

Virginia Standards

6th Grade SOLs » Science » 6.1
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