DON’T call these relics ‘space junk’! 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. For example, the Apollo astronauts couldn’t clean up the ALSEP sites and bring back home all the packaging (see picture below, credit: NASA): if they had done so it would have been at the expense of the precious lunar rocks and their very short time on the surface doing science. Unfortunately, as of today, there is no other viable option to guarantee mission success and there are no means to retrieve them.
Thus, ‘derelict objects’ is a more appropriate word to qualify them and they can be classified into three groups:
While all cases should be remediated, both latter groups must be emphasized to mitigate consequences. This catalogue is a step in this direction.