The number of objects in Earth's orbit, including satellites and debris, is significantly increasing, raising concerns about potential collisions.
Orbiting Objects and Debris
Mars Buttfield-Addison, a computer scientist specializing in space debris, states that approximately 33,000 objects are large enough to be individually identified from Earth.
This figure does not include millions of smaller fragments that are too small for reliable ground-based observation and cataloging.
Since 1957, an estimated 17,500 satellites have been launched into orbit, with over 12,000 of these launches occurring in the past six years. Starlink, for example, maintains a constellation of about 9,600 small spacecraft, representing over half of the active satellites currently in orbit.
Collision Risks
Despite the growing number of objects, the vastness of space means that actual collisions remain rare. However, specific orbital zones are becoming more cluttered. The Low Earth Orbit (LEO) zone, located less than 1,000 km above the surface, is now a primary concern due to the high density of objects.
Objects in LEO travel at speeds of 27,500 km/h or more. Many satellites in this zone lack propulsion capabilities, making collision avoidance difficult if two craft are on a collision course. Evidence of collision risk includes puncture damage on spacecraft, such as the space shuttle Atlantis and the International Space Station's Canadarm2, caused by micro-meteoroid orbital debris.
Satellite Visibility and Identification
Many satellites, including the International Space Station (ISS), are visible to the naked eye just before sunrise or after sunset, appearing as they reflect sunlight. The ISS, the largest spacecraft produced at 109 meters in length, orbits at 27,600 km/h and requires monthly boosts to maintain its approximate 420 km orbit due to atmospheric drag.
Observers identify and track objects in orbit using a combination of optical telescopes and radar. Radar can provide insights into an object's shape, which is often more informative than visual observations alone.
While many low Earth orbit satellites support internet services, numerous others perform critical infrastructure functions that are not always immediately apparent.