Before calling these relics ‘space junk’, it must be remembered that mass and space exploration are not compatible: a spacecraft can’t afford trailing unnecessary load, so items that are no more useful at one point into the mission become dead weight and must be shaved off quickly. As of today, there is no other viable option to guarantee mission success and there are no means to retrieve them.
Space junk can be classified into three groups:
Both latter cases must be emphasized and remediated to mitigate consequences. This catalogue is also a first step in this direction.