Since 1957, over 4700 satellites have been launched into space by nearly 30 countries. Along with spent rocket bodies and other debris, the total number of objects tracked by NORAD over the years comes to 23,700+. Most have long since decayed, leaving about 7,950 objects in orbit today. One enters or leaves the space over the continental United States every 2 seconds, so keeping track of them is a full time job for the US Space Command and NORAD.