Crazy Engineering: The Camera that Fixed Hubble

It's 1990 and we just got the first images back from the Hubble Telescope but there's a big problem. The pictures are out of focus. How do you solve that? Well first of all, you're going to need one of these. That's the space shuttle Endeavour and it was used in one of the greatest engineering fixes in history. We'll talk all about that on this episode of Crazy Engineering.

(Music Open)

The Hubble telescope is composed of several different instruments, and outside of those is something called the primary mirror, where all the light bounces off and goes into the instruments -- that's where the flaw was.

The problem was something called spherical aberration. What exactly does that mean?

It means the primary mirror had the wrong shape. That is, it's a shallow bowl, effectively, that brings light to a focus.

It was a little too shallow. It rendered the telescope fundamentally unfocusable.

So it was a little bit out of tolerance in that primary mirror and it was effecting all the instruments in Hubble?

All five scientific instruments on the Hubble depend on a sharp image. That's the whole point.

So Hubble is sitting in the doctor's chair. It has the eye chart in front of it and instead of the letter E it sees the letter F.

Worse! What it sees looks like a squashed spider.

But it's way up in space and you can't get it back here, so how do you fix it?

Well, if you're born with eyeballs that don't quite work, you don't go and buy new eyeballs, you get a pair of glasses. And that's the approach that we took.

The wide field and planetary camera, known as WFPC, relied on light from the primary mirror.

The light from that primary mirror all comes down to a focus inside our camera on a mirror that looks just like this. And this is now an opportunity for us to correct the curvature, the shape of the primary mirror right here. We simply put the same error in, reverse and correct it.

The Hubble Telescope was designed from the outset to be serviced every three years by astronauts.

(Astronauts talking)

The camera is designed to be replaced in space. That's the one thing really just waiting for us to take advantage of.

(Astronauts talking)

So what was the outcome? At the Space Telescope Science Institute, way down in the basement, there were a bunch of us watching. And the first image, which was a star, looked good. So we knew right away that we had a fix and everything that Hubble was suppose to do was now going to happen.

I think I speak for everyone when I just say thanks to you and your team for all the hard work you put in fixing Hubble. Because now we have these images really forever that we can appreciate.

(Music)

WFPC2 went on to become the workhorse for Hubble telescope and it lasted for more than 15 years. Well, now you guys can check it out at the National Air and Space Museum in Washington D.C. and we'll see all of you on another episode of Crazy Engineering.