Hubble Repairs Tricky

Caption for this picture, courtesy of NASA:

(14 May 2009) --- Astronaut Andrew Feustel, STS-125 mission specialist, appears to be selecting his next tool to use while participating in the first of his crew's five scheduled sessions of extravehicular activity to perform final hands-on servicing of the Hubble Space Telescope. Feustel and veteran astronaut John Grunsfeld (out of frame) are scheduled to participate in a total of three of those spacewalks.


The shuttle Atlantis mission to repair and upgrade the Hubble Space Telescope is continuing. Today, according to the Washington Post, they will be performing the trickiest operation yet:

Now [astronaut John] Grunsfeld has begun the most daunting task of the mission: He must repair the non-functioning Advanced Camera for Surveys (ACS), which was never designed to be repaired -- not on Earth and certainly not in space.

The spacewalker must extract 30 screws, remove a protective plate, and reach into the ACS with a specially designed tool that will clamp onto four sharp electrical circuit cards. He'll remove the cards -- being careful to keep his gloved hands away from any sharp edges -- and then install a new power source to the instrument.

Grunsfeld's task will be made all the more difficult by the awkward position of the instrument. He will not be able to face the screws head on, but rather from a 45-degree angle. A strut will partially block his vision.

Astronauts Having Success on Tricky Hubble Repair

The last paragraph describes the sort of thing that prompts curses from electronics technicians and auto mechanics. You do them as much by feel as by vision. Doing something by feel is a tough thing to do when you're wearing a space suit.

Of course, space suits are only part of the problem. On Earth, when an electronics tech yanks a circuit board out of a computer, gravity is holding his feet to the floor, or his butt to the chair, and his muscles can counteract the force being applied to his hands in reaction to the force he's applying to the board. In Earth orbit, there's no gravity. To get an idea what that's like, imagine you're underwater in a pool that's too deep to stand in. Push against the side of the pool with one hand. You'll spin around, because the force is being applied to your hand, and your body in turn.

Image credit: NASA

This is one of the reasons spacewalks are practiced underwater. In the photo that leads this article, the Canada Arm is providing the needed stability, but it won't feel much like the way that works on Earth.

One of the great things about having a space vehicle like the shuttle is that it makes repairs like this possible. It can bring all the parts and the astronauts to replace them. No doubt some of these things could be done by remote control, without taking human beings into space, but, as the WaPo story relates, sometimes humans need to be there to adapt to unforeseen problems:

The first spacewalk, also conducted by Grunsfeld and [Andrew] Feustel, was stymied initially by a bolt that wouldn't budge and threatened to trap an old instrument in the telescope and ruin the hopes of scientists and engineers who had spent a decade building a replacement. The astronauts used three different tools with ever higher amounts of torque, to no avail. There were fears both in space and on the ground that the bolt would shear. But Feustel, who fixes cars in his spare time, removed all limits on his socket wrench and, carefully applying ever more force, managed to loosen the bolt without shearing it.

Astronauts Having Success on Tricky Hubble Repair

Pretty amazing, under the circumstances.