Astronaut Jeffrey Hoffman removed the Wide Field and Planetary Camera 1 (WFPC 1) during the first Hubble servicing mission (SM1), which took place in December 1993. Image credit: NASA
25 years ago this week, NASA held its collective breath as seven astronauts on space shuttle Endeavour caught up with the Hubble Space Telescope 568 kilometres (353 miles) above Earth. Their mission: to fix a devastating flaw in the telescope’s primary mirror.
About the size of a school bus, the Hubble Space Telescope has an 2.4-metre (eight-foot) primary mirror. The largest optical telescope ever launched into space, where it could observe the universe free from the distorting effects of Earth’s atmosphere, Hubble had a lot riding on it. But after the first images were obtained and carefully analysed following the telescope’s deployment on 25 April 1990, it was clear that something was wrong: The images were blurry.
Astronomers and engineers rallied to study a variety of solutions to the problem, and NASA convened an independent committee to find the source. They all came to the same conclusion: Hubble’s primary mirror, which looks like a very shallow bowl, had been polished into the wrong shape. The error was smaller than the width ...