Hubble Space Telescope
1990-present
The flagship space telescope. Launched 25 Apr 1990 on Discovery with a 4.2 m mirror, far above the atmosphere that blurs ground-based views.
Specs
11,110 kg; ~540 km orbit; 5 Shuttle servicing missions (1993-2009); 1.5M+ observations; helped measure the age of the universe (~13.8 billion years).
Why it matters
Its five servicing missions - astronauts swapping gyroscopes and cameras in orbit - are impossible in a world without real space. The 1993 repair of its mis-ground mirror is one of the great engineering stories.