Week Five: The Science of Satellites

This week in class we focused on satellites and how exactly they stay in orbit up in space. For most people, me included, space is a very abstract idea. We know that it's there, but we don't really understand how it works. Space is devoid of a lot of things integral to our daily lives like sound and gravity, so it seems more like fiction than reality. In order to grasp how satellites "fly" through space, we first had to learn how things fly on Earth. The adaptation of flight has happened separately four times with birds, bats, insects, and pterosaurs. Some factors that affect flying in winged animals is weight and air resistance. Both these things have no effect on the things orbiting in space, though, since there is no drag or weight in the vacuum outside our atmosphere. There is still gravity acting in space, but it is not as strong as when we are on Earth. In the Manuel “The Physics of Space Security” I learned that when satellites travel through space, Earth is constantly pulling it toward its center. This brought up my initial question of why doesn't the satellite just fall back to the earth then? Well, as the satellite continually falls, the earth is constantly curving away from it, creating a path for the satellite that remains parallel to the earth’s surface while in orbit. I was still a little fuzzy on this concept at first, but then I learned one visual that really helped me out. Think of if you were to spin a string with a ball tied to the end in the air. The ball moves in a circular “orbit” around your hand. This is basically the same thing going on with satellites, just the string is invisible. The “string” in space is Earth’s pull of gravity on the satellite. Just as if the ball would fly off if it broke from the string, a satellite would zoom off into space if Earth’s gravity was not holding it back. Thus equal and opposite forces of the earth’s gravity and the satellite’s inertia help to create the orbital path a satellite follows.
Satellites have many different uses in the world today, and I found a few different types through some further research:

Geostationary Operational Environmental Satellites, or GOES are used for collecting data on weather. Launched in April of 2010, GOES 13 is the current GOES East, responsible for remote sensing of the eastern United States.
                                        

An infrared image of the eastern United States taken by GOES 13

http://www.goes.noaa.gov/goes-e.html

Global positioning satellites, or GPS circle the earth at a medium orbit, completing revolutions twice daily. There are 27 operational GPS satellites currently.  Together, they create a net of satellites that can track where you are and give you directions to a place you want to be.  GPS was originally used only for the military, but in recent years became open to public use. The Block IIF satellite launched in 2010 and is planned to remain functional until 2025. 

  

The Block IIF GPS

http://www.gps.gov/systems/gps/space/ 

 

The Terra and Aqua satellites are NASA satellites dedicated to data collection concerning various environmental systems.  For example, with Moderate Resolution Imaging Spectroradiometer, MODIS for short, the satellites are able to record “net product productivity,” or the amount of carbon turned into other matter by plant life.  This tool also collects data on fires and their effects. From the collected data, scientists are able to learn more about the carbon cycle and how it is changing in the present day.

 

A picture of Earth captured from the Terra satellite

http://www.spacetoday.org/Satellites/TerraAqua/TerraStory.html 

 Sources:

Reibeek, Holli. "The Carbon Cycle." Earth Observatory. Ed. Michael Carlowicz. NASA, 16 June 2011.

http://www.goes.noaa.gov/goes-e.html

http://www.gps.gov/systems/gps/space/

http://www.spacetoday.org/Satellites/TerraAqua/TerraStory.html