When Hubble Space Telescope was launched, it had a big problem: It couldn’t see very well. NASA had allowed it to fly with a flaw in its main mirror, which blurred its view of the cosmos. But 25 years ago this week, a crew of astronauts set out to fix the problem.

The crew of mission STS-61 grabbed Hubble from orbit and secured it in the shuttle’s cargo bay.

During five spacewalks, the astronauts installed a set of corrective lenses and a new camera to sharpen Hubble’s view. They also replaced Hubble’s solar panels. The old panels “flapped” as their temperature changed, creating a jiggle in the telescope. And they replaced or upgraded gyroscopes, computers, and other systems. They then released the telescope to continue its work.

The repairs were a big success. Hubble began snapping remarkably clear pictures of the universe.

Four more servicing missions followed over the next 15 years. Each one improved Hubble’s capabilities. And the telescope is still working — thanks in part to the past visits from astronauts.

Script by Damond Benningfield