This is an important experiment but the article has a dearth of technical information that would be interesting to the casual subscriber to this Reddit. They are targeting the second stage of a Vega launcher which I think is known as a Zefiro 23 with a gross mass of 26,900 kg (59,300 lb) and unfueled mass of 3,000 kg (6,600 lb) and a length of 7.5m.

I assume it's not tumbling or spinning too much as I'd assume they would aim for a relatively easy target although it looks like it's a pretty good size. I also assume that they will just grab the booster and then de-orbit the entire thing.

I'm thinking that it would be cool if you could catch and de-orbit multiple items by having some sort of ejection mechanism. This obviously would be enormously complex and be constrained to searching out debris with similar enough orbits so that you could capture more than one during a mission. In any case I hope it works.