What Is GPS?

GPS Satellite GPS stands for Global Positioning System. It was originally designed by the U.S. military and is currently operated by the U.S. Defense Department. It’s official title is NavStar.

The GPS system is made up of at least 24 satellites which constant move in a very precise orbit 12,000 miles above our heads. They are powered by the sun but have battery backups so they do continue to run even if the sun is temporarily blocked (such as during a solar eclipse!). Each of the 24 satellites have rocket boosters to keep them precisely in their orbit. They weigh around 2,000 pounds each and with the solar panels fully extended, measure about 17 feet wide. The first satellite was launched in 1978.

The satellites only have a life expectancy of around 10 years or so – meaning a constant program of replacements being built and launched. The cost comes in at around US$750 million per year.

The Public GPS Navigation System

In 1983 the GPS was made available to the public. It is still maintained by the U.S. Defense Department without charge for use by the public.

The orbiting satellites move around the earth twice a day, continuously broadcasting their location. A car GPS system can tell how far away a satellite is by comparing the difference between the transmission time of the signal and the time it was received. The longer it takes the signal to reach your car receiver, the further away the satellite must be. By adding in the information from 2 other satellites, the precise position of your car can be calculated.