: The 72 Iridium communications satellites, which provide service for Iridium satellite cell phones, also provide periodic light shows. The highly reflective material, on the three 76x34 inch antennae each satellite has, periodically provide a flash of light that is visible to people in earth. This 5-20 second light, brighter than anything else in the sky (except the moon), can be seen from the ground, when the sunlight reflects off the 780 kilometers high satellite. This event has caused a number of UFO sighting reports, as have similar flares off some other low orbit satellites. The heavens-above.com site gives a schedule of where, and when, these light flares can be seen. Many low flying satellites can also be clearly seen with consumer grade portable telescopes. Some governments have much larger telescopes built for getting a closer look at low flying satellites, the better to take detailed photographs, and just keep track of whats going on up there. But anyone can go to http://science.nasa.gov/Realtime/JPass/20/ and enter your location, and get a list of satellites that will be passing over you, and your low power telescope.