In 1990, after decades of lobbying to get it built, NASA launched a telescope designed to give humanity its clearest view of the universe ever — and it came back blurry. Here's how a broken mirror became the most important eye in the sky.
Astronomer Lyman Spitzer first proposed putting a telescope in orbit in 1946, arguing that Earth's atmosphere — not our instruments — was the real limit on astronomy. It took him almost 30 years of lobbying before anyone funded it.
Hubble was originally set to launch in August 1986. The Challenger disaster that January grounded the entire Space Shuttle fleet for over two years, pushing Hubble's launch back nearly four years.
On April 24, 1990, Space Shuttle Discovery finally carried Hubble into orbit — the telescope Spitzer had spent three decades fighting for, now above the atmosphere it was built to escape.
Weeks later, NASA discovered Hubble's primary mirror had been ground 2 microns off — about 1/50th the width of a human hair. Every image came back blurred, and the failure became a punchline on national TV.
In December 1993, seven astronauts spent 10 days and five spacewalks installing corrective optics on Hubble — fitting a telescope with glasses, by hand, in orbit.
Once fixed, Hubble pointed at a patch of seemingly empty sky for 10 straight days in 1995. It found roughly 3,000 galaxies no one had ever seen — the Hubble Deep Field.
Astronauts serviced Hubble five times between 1993 and 2009 — the last spacewalk repairs any spacecraft has ever received. When the Shuttle program ended, those house calls stopped for good.
Despite 36 years of headlines, Hubble has never left low Earth orbit. It circles the planet at roughly 340 miles up — only about 90 miles higher than the International Space Station — completing a full loop every 95 minutes.
Hubble isn't always in view of a single ground station, so NASA relays its signal through satellites parked over 22,000 miles up in geostationary orbit — meaning data from a 1990s spacecraft travels farther after it leaves Hubble than before.