Former Nasa project scientist Mark Clampin explains: “Because it’s such a big and complex observatory, and also because it has to work at cryogenic temperatures, you can’t just put everything together at once, and then test it. You put everything into sealed, thermally isolated packages, starting with the smallest pieces and working upwards, testing at every stage. And then as everything gets bigger and bigger, it becomes virtually impossible to go back because you found a problem in a detector, let’s say.”
