We have gotten used to using satellite navigation in our daily, from helping us find our way to the store to docking ships. It has become such a heavily used item that it would seem the akinks in the system have been all worked out. However, there is one thing that can have a damaging effect on our sat-nav systems that has gained more attention among astronomers lately: the fact that the Sun has passed its solar minimum and is moving back toward its solar maximum.
The Sun goes through what is called a solar cycle on average every eleven years, with swings between high and low activity. These active periods occur when a high number of Coronal Mass Ejections (CMEs) are emitted from the Sun. These solar flares send out huge bursts of magnetic energy into the surrounding space and some of them are sent in Earth’s direction. These high energy particles can affect the satellites that are involved with the sat-nav’s systems.
There are a large number of satellites circling the Earth. The way the satellites create accurate information for the sat-nav programs is through relatively simple geometry. Satellites send information back to Earth through a radio signal that holds two essential pieces of accurate information. One piece is where exactly that specific satellite is, and the other piece is the exact time. This allows the sat-nav to receives this information from whichever satellites it happens to be in alignment with at the time, and since there is a whole fleet of them, military and civilian, there is enough to work out exactly where it is through a simple triangulation calculation. Once the sat-nav collects this information it can determine its position bases on how far it is away from the satellites combined with how long it took the signals to arrive.
The problem arises when the radiation coming from the Sun’s CMEs interferes with these signals and makes it much more difficult for the sat-nav to find the weak signal that the satellites send to Earth.
The only way we have to counter this at the moment and for the foreseeable future is the use of complex directional antennae, which are expensive and at the moment used almost solely for military applications. It is still incredibly difficult to obtain such equipment for commercial industry due to heavy regulations set by the military. Even if this information was released to non-military users in the US and selected allies, due to export controls on the actual products it would be near impossible to get this information to a number of companies that might fall out of the specific boundaries of the requirements listed by the US government.
Another problem arises when the signal that is sent has to travel through the ionosphere, the outer atmosphere of the Earth. The ionosphere is mostly made up of a collection of particles that have been ionised, or been ripped apart by the Sun’s activity. The more active the Sun, the more radiation enters the ionosphere and the greater the potential for interference with sat-nav.
This can have a negative effect because the technology assumes that the signal that has been sent by the satellite has been sent at a constant speed and continues to travel at a constant speed, but that is not automatically true, since the greater the interference from the Sun through increased activity the more slowly the signal may pass through the ionosphere, resulting in greater distortion of the speed of the information being transmitted to Earth, adding error to the system’s calculations.
There are other factors that can interfere with information in similar ways, but the sun’s cycle has a more powerful and longer lasting impact. The reason why scientists have not had to consider it before is because the last time we had a solar maximum the technology had not reached a point where it was so precise, nor was it so essential to our lives. In this Information Age disruptions of communication can be devastating and we must be ready for trouble.