We rely on our smartphones for plenty of daily tasks, without even thinking that the advances in the space industry back up the connectivity behind this tech. Of the many possible uses for satellites, maps and navigation are usually the first that come to mind. And even though everyone has heard of the ‘GPS system,’ few people actually think of how it works. Below, we’ll quickly explain how GPS works with satellites and list other navigational systems developed outside the US.
GPS System How It Works
GPS stands for global positioning system. It was first launched in the US in 1978, but it only became globally available in 1994. Besides the US-made GPS, there are several other operational systems, including Russian GLONASS and European Galileo. Their operation logic is very similar, but since most of the world’s population relies on GPS, let’s see how it works exactly.
There are three main components of a GPS system — space segment, control segment, and user segment. The US Air Force is responsible for the first two — space & control. The agency not only develops and operates these segments, but also maintains them.
The space segment is a constellation of satellites located in medium Earth orbit (MEO), over 20,000 km above our planet. Satellite constellation in the GPS system is essential because just a few spacecraft would not be able to ensure the speed and accuracy we’re used to. Out of 31 total satellites in the GPS system, 24 must be operational at least 95% of the time. GPS system satellites send one-way signals back to Earth, which is exactly where the control segment comes in.
The control segment is essentially a ground station with huge computing power to maintain and control GPS and satellites that send signals back to Earth. Of course, given the number of satellites in the GPS system and the coverage these spacecraft should provide, there are not one but several ground stations.
The control segment system, aka Operational Control Segment, is a global network of ground stations that ensures uninterrupted satellite control and maintenance. This includes making sure all spacecraft stay in required orbits, which sometimes for additional maneuvers and even satellite clock adjustment. A total of 16 facilities with 11 command & control antennas ensure our smartphone apps are always ‘online.’
Since the control segment is so important, it is also very complex. This system also has three major components — monitor stations, master control station, and ground antennas.
Monitor stations track satellites, receive their signals, and send them to master control stations. Master control is responsible for the overall command and control of the entire GPS satellite system constellation. It calculates satellites’ precise location, sends command messages to orbit, ensures all spacecraft are functioning properly, and repositions satellites if necessary. Master control station maintains satellites, resolving any issues as they arise. Besides, the master control station has backup — an alternate station with the same purpose.
Ground antennas are necessary to send commands from the master station to spacecraft. Antennas also collect telemetry, provide anomaly resolution and early orbit support — all via S-band communication.
The final segment is the user segment — one we all have access to. It includes a standard GPS receiver that gets satellite signals and transforms them into comprehensive data that keeps us from losing our way. But have you ever thought that a GPS system is not only about maps? If not, keep reading for other GPS system applications.
Additional Uses of GPS System in Satellite Communication
GPS with satellite imagery is the cornerstone of our entire communication system. This tech is now available practically everywhere, not only in our phones and smart watches but also in ATMs, shipping containers, and vehicles.
Global positioning system affects cargo movement, shipments and delivery, farming and construction, as well as overall logistics and supply chains. All major communication networks, including finance and banking, depend on this technology. In fact, many wireless devices would not be able to operate without GPS.
This tech is vital for timely rescue missions, transport accident prevention, state security, etc. Global positioning adds its share to scientific research, monitoring natural disasters, endangered species, and weather forecasting.
As you can see, our lives would be very different without GPS. Along with GPS, you may have heard about GNSS. Are these two any different? Well, yes and no. GNSS stands for global navigation satellite systems, which means it is a broader term than GPS. GNSS is a collective term for similar systems developed worldwide, including Russian GLONASS, ESA’s Galileo, Asian BeiDou, as well as purely regional systems, such as NavIC (NAVigation with Indian Constellation) and QZSS (Quasi-Zenith Satellite System).