In almost 60 years of space activities, more than 5200 launches have placed some 7500 satellites into orbit, of which about 4300 remain in space. Only a small fraction − about 1200 – remain operational. This large amount of space hardware has a total mass of more than 7500 tonnes.
Not all objects are still intact. More than 23 000 (as of January 2017) are regularly tracked by the US Space Surveillance Network and maintained in their catalogue, which covers objects larger than about 5–10 cm in low-Earth orbit and 30 cm to 1 m at geostationary altitudes.