The U.S. and about 50 other countries currently have satellites in orbit around the earth for various commercial and military uses ranging from communication to observation like those used by Google to take pictures of the earth. However, these satellites are constantly under threat of colliding with pieces of space debris moving at hundreds of miles per hours.
When a satellite is destroyed or a missile detonates in orbit, bits of metal and other materials are left over in orbit. Some of these pieces can be fairly large, and can move very fast. Larger bits of space debris are capable of destroying satellites, costing millions in damage. Other, smaller particles of space debris come from coolant exhaust or spent rocket fuel. These sand like particles are capable of blasting satellites over time, causing serious damage.
Sand like space debris is easily neutralized by coating a satellite in foil to vaporize the particles before they reach the satellites hull, but exposed devices, such as solar panels and optics are still left vulnerable. Larger bits of space debris are not so easily neutralized, however they are easier to detect and therefore avoid. The SSN (Space Surveillance Network) is used to track satellites and debris particles with a diameter larger than 10cm. The information from the SSN is used to alter the orbits of satellites that are in danger of being hit by space debris so that collision can be avoided.
Seing how space debris is such a serious problem, there have been several suggestions to rid the space above our planet of these harmful objects. One of the main ideas is to use giant "nets" that would collide with space debris and trap it, eventually falling back to earth and burning up upon reentry. These nets would be composed of closely intwined, thin metal threads. Another proposition has been to use ground based lasers to target debris and push it out of a harmful path or to destabilize its orbit and send it back to earth.
Whatever the solution, space debris could pose a serious threat to our space based infrastructure. If even one satellite is destroyed, it becomes space debris and could threaten other satellites and turn them into space debris, potentially causing a chain reaction that would make orbital satellites impossible. This scenario may not be very likely, but if it should happen we would lose GPS navigation, satellite TV, and any number of things to which we have grown accustomed.