There are approximately 900 active satellites in orbit around Earth [source: Union of Concerned Scientists]. Launching a satellite is no small matter. It can cost millions of dollars to develop a satellite, construct it, and place it into orbit. Satellites need occasional boosts to remain in orbit. That means engineers have to factor in the weight of fuel on top of the satellite itself.
Space weather can decrease the lifespan of satellites in many ways. If the sun emits a coronal mass ejection (CME), the radiation and particles can interfere with satellite operations. Ionizing radiation can weaken a satellite. The energy may also heat up the atmosphere, making it expand. A satellite in low orbit could experience atmospheric drag and be in danger of falling without a boost. Since there's a finite amount of fuel aboard a satellite, each unplanned boost decreases its useful life.
The magnetic shockwave that accompanies solar activity is also a problem. Unless a satellite is shielded properly, the magnetic fluctuations could induce electricity within the satellite itself. The satellite might not respond to commands properly or it might give erroneous readings to ground control. Among the particles traveling from the sun during a CME are electrons. Even a single electron can cause problems if it penetrates a satellite's shielding.
Many military satellites have thick shielding -- why not apply that to all satellites? The answer to this question boils down to risk versus reward. Shielding adds weight to a satellite. That means the satellite will be more expensive to launch and, depending upon the orbit of the satellite, it may need boosts more regularly than lighter satellites. If the expense of putting the satellite into orbit is greater than the benefit of having it there in the first place, it doesn't make sense to launch.
What the SPACECAST project hopes to do is study the effects of solar activity on satellites with the goal of designing future satellites to be resistant to those effects without escalating costs. Part of SPACECAST's mission is to create early warning detection systems that might allow satellite operators to adjust a satellite's orbit or power down nonessential systems to minimize the effects a solar storm might otherwise have on the device. With enough notice, operators could also reroute satellite communications to other satellites that aren't in the path of a solar storm.
We've already seen what can happen to a satellite as a result of solar activity. On Jan. 20, 1994, two communications satellites called ANIK E1 and ANIK E2 suffered internal failures because of deep dielectric charging. Electrons moving with intense energy penetrated the shielding on the satellites and caused malfunctions. It took eight hours to regain control of E1 and seven months to bring E2 back to service [source: Horne].
The dangers don't end there. Should we have astronauts in orbit during a solar storm, they too would be vulnerable to solar activity. SPACECAST will help determine the type of safety measures we need to consider to keep astronauts safe during solar events. That could include creating safety rooms inside spacecraft and space stations that have thick shielding as well as procedures designed to shut down nonessential systems during a solar storm.
The sun's activity can also affect electronics here on Earth. Next, we'll look at how a solar storm can shut down a power grid.