The telescopes that left Earth

A 2.4-metre mirror parked above the atmosphere in 1990, launched with a flawed figure, repaired by hand, and still returning science more than three decades later.

An X-ray telescope whose mirrors do not face the sky at all — light skims across them at a grazing angle, which is why the two numbers you would normally ask for do not exist.

A 6.5-metre segmented infrared mirror that had to be folded to fit inside a rocket, unfolded a million miles from Earth, and kept below 50 kelvin to see anything at all.

The same 2.4-metre mirror size as Hubble, arranged to see a hundred times more sky at once — a survey machine rather than a portrait lens.