The difficult task of making a comprehensive inventory

The exact number of artificial objects in outer space will never be known. It largely depends upon:

  • How objects are numbered, for instance a flag may be counted as one object or split into its elements (cloth, staff, crossbar, etc.);
  • The number of debris resulting from impacts, collisions and spent stage breakups, provided those events will ever be known;
  • The number of objects that emerge from deployments and separation of spacecraft (explosive bolts, lens caps, dust covers, clamp bands, fairings, shrouds, etc.);
  • Untold or unknown events such as classified missions and experiments, private belongings secretly left on the moon by the Apollo astronauts, family items hidden into space hardware by mission staff and technicians, or Apollo hardware unofficially returned to Earth as souvenirs by the astronauts.