Eyes in the Sky: WebQuest Satellites
We can all picture Earth, suspended in space like a giant blue and green marble. We imagine it that way only because at some point we've seen photos from space. While most of these memorable shots were taken from moon missions, there are other eyes in the sky, called satellites, that take photos of Earth every day.

Even though they are invisible, satellites are part of our daily lives. Satellites give us pictures that help with weather reports. Satellites send most of the TV shows we watch to the TV stations. GPS and NAVSTAR systems help people in cars and planes get to the right place. And lots of satellites help scientists watch the Earth to see changes in the ocean, in forests and in the places where people live.

What is a Satellite?
A satellite is any object that revolves around a planet in space. The moon is Earth's original, natural satellite, and there are many manmade (artificial) satellites. The moon is 240,000 miles away. Most satellites are between 100 and 24,000 miles away.

Anything that is in orbit around Earth is a satellite. But the word "satellite" usually means a useful object placed in orbit on purpose to perform some specific job.

The Hubble Space Telescope is the most famous scientific satellite, but there are lots of other satellites looking at everything from sun spots to gamma rays. Earth observation satellites photograph the planet and can see changes in everything from temperature to forestation to ice-sheet coverage.

Fast Facts

  • Most satellites are custom built for one type of job. There are a few exceptions though -- like GPS satellites with over 20 copies in orbit.

  • There is a "satellite parking strip" over the equator. Hundreds of TV, weather and communication satellites fly in this strip. This congestion means each satellite must be precisely positioned to prevent satellite signals from interfering with each other. The satellites here hold an altitude of about 22,223 miles, or about a tenth of the distance to the Moon.

  • All satellites today get into orbit by riding on a rocket or by riding in the cargo bay of the Space Shuttle.


  • For speedy production, some newspapers and magazines transmit their text and images to multiple printing sites via satellite to speed local distribution.

  • Emergency radio beacons from downed aircraft and distressed ships may reach search-and-rescue teams when satellites relay the signal.

  • A satellite launch can cost anywhere between $50 million and $400 million. And an entire shuttle mission costs half a billion dollars (a shuttle mission could easily carry several satellites into orbit).

  • Photos from space can be surprisingly detailed. For example, using what are essentially large telescopes that take pictures, military satellites can actually "see" and photograph people outside a military base or compound.
(Other interesting facts can be found in the article, How Satellites Work on the HowStuffWorks Web site.)

WebQuest Online Exercise
In this journey around the Web, we'll investigate all sorts of satellites - GPS satellites, Earth observation satellites and much more. You'll find out what these satellites are looking at and see many of the images for yourself.

  1. The first man-made, Earth-orbiting satellite was launched on October 4, 1957 by the Soviet Union. What did they name this satellite? And, what does that name mean in the Russian language?

  2. How much does a GPS satellite weigh? How fast do GPS satellites travel? And, how many GPS satellites are in orbit right now?

  3. Where can you "see" Fenway Park, the Biltmore House, Disney World's Magic Kingdom, the Daytona Speedway and Central Park all in one place? This Web site features satellite images of all these famous places and more.

  4. Did you know that you can see the International Space Station without a telescope? It's true. For example, if you live in the Raleigh, North Carolina area, you should be able to see the International Space Station from 6:04 a.m. to 6:07 a.m. on September 8, 2004.

  5. What are the three basic types of satellite orbits?

  6. What causes space junk?

  7. Red tides can be very dangerous -- killing large numbers of fish and causing health problems in humans. Find out how satellites can be used to help in the early detection of this hazardous phenomenon.

  8. What do thermal blankets, solar arrays, flight computers and digital cameras all have in common? They can be found on a satellite. Visit the following Web site to see the anatomy of a satellite.