All to repair and upgrade the Hubble space telescope at 350+ miles above earth. About double the height of the Internatinal space station. From the link above:
Astronauts will also install a new imaging camera and a Cosmic Origins Spectrograph -- an especially sensitive instrument designed to split light it captures into individual wavelengths.
The spectrograph, NASA says, will not only be able to study stars, planets and galaxies but also basic elements found throughout the cosmos, such as carbon and iron.
And the new instruments will allow Hubble to peer even further back into time, perhaps as far back as some 600 million years before the Big Bang, much further than the billion years it can reach back now.
When one considers the knowledge that has been gained from Hubble, and the potential new knowledge that will result from this mission, one cannot help but feel like the tiniest wee speck of insignificant stuff. Our knowledge of the size and scope of the cosmos is staggering thanks in large part to Hubble. Hazardous as it may be, the mission to repair Hubble is worth the risk.
The work is hazardous, indeed. Monkeying around with sharp objects while wearing a space suit is no easy task. A tear in the suit, which is a possibility in this kind of mission, would surely mean instant death for the unlucky astronaut. There is also the space junk and micrometeorites which may damage the shuttle, making re-entry impossible. The astronauts on this mission are brave souls with ice water in their veins.