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"The ability to put a metric tonne on the surface... gives us the capability to undertake sample collection," says Dr McCuistion. "To collect and launch samples back into orbit will require that size of a vehicle."

He will leave the post in May to be replaced by Ian Tyler, former chief executive of Balfour Beatty.

The border security operation - codename Agata - was first carried out in 2011 and usually takes place three times a year.

Every piece of equipment is run through a complex computer programme, which assesses whether it is worth bringing home, selling locally, or scrapping.