Editing Space weather (section)

===Spacecraft orbit changes===
The orbits of spacecraft in [[low Earth orbit]] (LEO) decay to lower and lower altitudes due to the resistance from the friction between the spacecraft's surface (''i.e. '', drag) and the outer layer of the Earth's atmosphere (or the thermosphere and exosphere). Eventually, a LEO spacecraft falls out of orbit and towards the Earth's surface. Many spacecraft launched in the past few decades have the ability to fire a small rocket to manage their orbits. The rocket can increase altitude to extend lifetime, to direct the re-entry towards a particular (marine) site, or route the satellite to avoid collision with other spacecraft. Such maneuvers require precise information about the orbit. A geomagnetic storm can cause an orbit change over a few days that otherwise would occur over a year or more. The geomagnetic storm adds heat to the thermosphere, causing the thermosphere to expand and rise, increasing the drag on spacecraft. The [[2009 satellite collision]] between the ''Iridium 33'' and ''Cosmos 2251'' demonstrated the importance of having precise knowledge of all objects in orbit. ''Iridium 33'' had the capability to maneuver out of the path of ''Cosmos 2251 ''and could have evaded the crash, if a credible collision prediction had been available.