What is a satellite anyway?
For this project, we will generally classify a satellite as a man-made spacecraft that is moving around another object in space. In our case we are considering the machines that are in orbit around the earth. These objects have been intentionally placed there by humans for many reasons, but not limited to research, communications, weather prediction, navigation and even as a space telescope.
Where are those satellites?
There are three general location classes for earth-centric satellites.
Low Earth Orbit - defined as an orbit that is less than 1,200mi above the earth.
Medium Earth Orbit - defined as an orbit that is between LEO 22,236mi above the earth.
Geostationary/Geosynchronous Orbit - defined as an orbit that is at 22,236mi above the earth. This orbit matches the Earth's rotational period, and thus appears in the same spot above the earth at all times. This is often referred to as the Clarke belt after the Sci-Fi Writer "Arthur C. Clarke".
Some famous satellites
Sputnik 1 - The first satellite. Lauched by the USSR (Russians) in 1957 officially starting the "Space Age".
Satcom F3 - One of the first generation of TVRO Geostationary (Clarke Belt) Communications Satellites. It was launched in 1981. Numerous people in the Cayman Islands got their first taste of live TV via this satellite using massive home-built dishes.
GPS - First prototype launched in 1978. It's what gives us our ability to use Google & Apple Maps etc. Per Wikipedia: A GPS receiver calculates its own four-dimensional position in spacetime based on data received from multiple GPS satellites.
It has a circular orbit that lies between 230 - 290 miles high. It's orbital speed is an average of 17,000mph taking 96 minutes for each orbit. This means it goes around the earth an average of 15.5 times per day. Thus we have opportunities to view it just after sunset and just before sunrise as it is illuminated by the sun.
The orbit of the ISS is predictable and there are numerous websites and mobile applications that can alert you when the station will be visible at your location.
Look up, you might just see it.
Otherwise known as "Space Junk".
Scientists estimate that there are hundreds of thousands of pieces of man-made "junk" orbiting the earth in Low Earth Orbit. Sitting within that debris is an estimated 23,000 pieces that are larger than 4". This is right where the ISS and many other active satellites are positioned. This "stuff" is travelling at speeds of greater than 20,000mph, and so can make a serious impact if it collides with these orbital vehicles. As recent as 2006 a tiny piece of "junk" chipped a window in the ISS.
These unintentional satellites have been accumulating since the launch of the first satellite Sputnik 1. It includes various discarded rocket stages, decommissioned satellites and small pieces of paint that have chipped off spacecraft.
What happens when an old satellite is no longer in use but can still broadcast?