NASA Launched Hubble Nearly Blind - Then Fixed It in Space

In 1990, NASA sent the most powerful telescope ever built into orbit - and almost immediately discovered it could barely see. Hubble's primary mirror had been ground to the wrong shape, and the world's most anticipated observatory was producing images so blurry it became a national embarrassment.

A Mirror Off by a Fraction

The flaw was almost unimaginably small. Hubble's primary mirror - 2.4 meters across - had been polished to the wrong curve. The outer edge was 2 microns too flat, roughly 1/50th the width of a human hair. But in optics, precision is everything. Instead of focusing 70% of incoming starlight to a single point, Hubble could only manage 10-15%. Every star appeared surrounded by a halo of scattered light. Every galaxy was a soft blur.

The cause was traced to a tool called a null corrector, used during fabrication to test the mirror's shape. A lens inside the device had been spaced off by 1.3 millimeters - a tiny error that had gone undetected for nine years. The result: Hubble had been polished to perfection - but to the wrong specification entirely.

A $1.5 Billion Punchline

The telescope had cost $1.5 billion to build and launch. Within weeks of its first images arriving, NASA found itself fielding congressional hearings and late-night jokes. Senator Barbara Mikulski publicly asked whether NASA was building "techno turkeys." Astronomers who had waited decades for Hubble to fly watched blurry images of galaxies they could barely identify.

Glasses for a Telescope

Engineers developed a solution called COSTAR - the Corrective Optics Space Telescope Axial Replacement. About the size of a large refrigerator, it used 10 small motorized mirrors to intercept light before it reached Hubble's instruments, compensating precisely for the original mirror's error. The concept was conceived by engineer James Crocker while studying the adjustable shower fixtures in a European hotel room.

In December 1993, Space Shuttle Endeavour carried seven astronauts to Hubble on mission STS-61. Over five consecutive spacewalks totaling 35 hours and 28 minutes, two teams worked in orbit to install COSTAR and replace the Wide Field and Planetary Camera. It was among the most complex repair missions NASA had ever attempted.

The Images That Came Back

When the corrected images arrived, Senator Mikulski's reaction was immediate: "My God, it's like putting my glasses on." The before-and-after photographs of galaxy M100 became iconic - a blurry smear transformed into a crisp spiral of stars. Hubble went on to produce discoveries that reshaped modern astronomy: the accelerating expansion of the universe, the age of the cosmos, the atmospheres of planets orbiting other stars. The telescope that launched nearly blind became the most productive observatory in the history of science.