GPS means Global Positioning System. It provides location based information, weather information and more. USA located GPS satellites since 80s and they are free to use for all people now. How many GPS satellites in the orbit?
Today it’s possible to use GPS on mobile devices and others by GPS chips. GPS chip is a special technology sending and taking signals from GPS satellites.
Today there are 30 satellites on the orbit. They have a codename called NAVSTARs. First GPS satellite sent to space in 1978 but it has usage now. We are using GPS satellites sent to space since 1989.
First group of GPS satellites sent to space between 1978 and 1985. Their lifetime was 5 years but some of them stayed there over 7 years. They were mostly using for their spy features but the feature that these GPS satellites have to be in contact with center was making them useless in spy games.
Second group of GPS satellites sent to space 1989 to 1990. They were travelling the orbit without contact to center for 14 days. So they used for military works mostly.
The third groups of satellites sent in 1990 to 1997 were over developed models. They were travelling over orbit without contacting to center for 180 days.
Today there are some special GPS satellites using for only military and others are only usable for location based data. It’s possible to use these satellites with GPS devices, mobile devices with GPS chip and car systems with GPS systems.