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Satellite Communications

Graphic of 2nd generation GOES satellite in orbit. Courtesy NOAA.

What...

• has helped rescue more than 41,000 people since 1982;

• shows the location of fi res, snow cover, thunderstorms, and erupting 

volcanoes everywhere on Earth;

 • lets you watch the lights go on all over North America as the sun sets?

Satellites, of course! But what keeps satellites in place? And how do they 

help send information all over the world? Here are two simple demonstrations that answer these questions.

What You Will Do

Demonstrate two of the basic principles 

that make satellites useful
National Oceanic and Atmospheric Administration (NOAA) 87

Science | SERVICE | Stewardship UNDERSTAND THE EARTH

What You Will Need

r Empty three pound coff ee can

r Poster board, at least 22-inches square

r String, about 12 inches long

r Pencil

r Scissors

r Marble

r Masking tape

r Flashlight

r Mirror

r Sheet of light-colored paper

r Two rooms connected by a doorway

r A partner

Warnings

Be careful with sharp scissors!

How to Do It

To show how satellites stay in orbit:

1. Tie one end of the string around the pencil. 

Hold the other end near the center of the 

poster board, and draw a circle about 22 

inches in diameter.

2. Cut the circle out of the poster board, then cut 

a wedge (pie shape) that is 1/8 of the circle.

3. Overlap the two edges of the circle where the 

wedge was removed to form a cone, and tape 

the edges together so that the cone holds its 

shape.

4. Put the pointed end of the cone in the coff ee 

can, and tape the cone to the sides of the 

can.

5. Roll the marble around the inside top of the 

cone as fast as possible, and observe the 

movement.

 When you push the marble forward and 

release it, the cone applies a continuous 

resistance to the marble’s movement and 

causes it to move in a circle. As the speed of 

the marble decreases, the gravity pulls the 

marble down to the bottom of the cone. If you 

could keep the marble moving at a constant 

speed, it would resist the pull from gravity 

and continue circling in the same place. When 

a satellite is launched, it moves away from 

Earth. Gravity causes a continuous pull on 

the satellite that keeps it from continuing to 

move out into space. Instead, the forward 

motion of the satellite keeps it moving in a 

circle around the Earth. 

To show how satellites help send messages 

between two points on Earth:

1. Have your partner stand in one room facing 

the doorway and holding a piece of paper. 

Your demonstration will work best if your 

partner is about six feet away from the wall 

that has the doorway.

2. Set up a mirror near the doorway in the other 

room so that the mirror is angled toward the 

doorway.
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Discover Your World With NOAA

88

3. Shine a fl ashlight toward the mirror. The light 

will refl ect into the other room so that your 

partner can catch it on the piece of paper.

The light is like messages containing information 

about Earth’s oceans, atmosphere, ecosystems, 

the location of people needing rescue, etc. These 

messages can be sent to satellites that relay the 

information to other locations on Earth that are 

thousands of miles away. 

Before satellites were available, messages were sent 

by bouncing radio signals off of Earth’s atmosphere. 

But because the atmosphere is constantly changing, 

radio signals don’t always bounce to the place that 

the sender wants them to go. Satellites are above 

Earth’s atmosphere, and are a much more reliable 

way to communicate.

There are two types of satellites. Geosynchronous 

satellites are about 22,240 miles above the 

equator, and travel at a speed (about 6,800 miles 

per hour) that matches the Earth’s rotation. 

This allows them to hover continuously over 

one position on the surface. Because they 

stay above a fi xed spot on the surface, they 

provide a constant lookout for the atmospheric 

conditions that trigger severe weather events 

such as tornadoes, fl ash fl oods, hail storms, and 

hurricanes. Polar orbiting satellites circle the 

Earth 14 times a day, at an altitude of about 500 

miles. These satellites pass almost directly over 

the North and South Poles, and view all regions 

of the Earth in a single day.

Want to Do More?

1. Visit http://www.goes-r.gov/resources/

education.html for resources designed to 

educate customers about meteorology, 

space science, earth observing systems, and 

benefi ts satellites will provide

2. Visit www.nesdis.noaa.gov/content/our-satellites to learn about our satellites, the 

history, how they work, upcoming launches, 

and how our satellites are part of a worldwide constellation that supports forecasting 

around the globe.

3. See www.bu.edu/satellite/classroom/model.

html for directions for making a model of an 

artifi cial satellite.

4. See www.sarsat.noaa.gov/sys-diag.html for 

information about how satellites are used for 

search and rescue.

Graphic of the Synchronous Meteorological Satellite, a geosynchronous satellite that was the forerunner of the GOES (Geostationary 

Operational Environmental Satellite) satellites. Courtesy NOAA.