Astronauts perform a myriad of types of jobs in space, from military, private and business affairs to the building, maintaining and repairing of the International Space Station (ISS). The launching, repairing and maintenance duties for objects like the Hubble Telescope, as well as military and commercial satellites, are carried out as needed as well, since only trained astronauts are able to leave the Shuttle and perform Space walks, usually tethered to the Shuttle or ISS, or to another astronaut who is structurally tethered.
When looking at an overview of the types of jobs astronauts perform in space, the building, expansion and maintenance of the ISS is the biggest and most time consuming of jobs. Safety is a major issue as the amount of tiny to very large pieces of "space junk", debris from objects in orbit that have crashed into other objects and broken apart, that are flying around at about 7-10 Kilometres per second. Even a tiny, 1-centimetre long piece of steel (or any material) could cause considerable damage to the Shuttles, ISS, Hubble Telescope, satellites and all other things flying around in Earth orbit. When an astronaut leaves the confines of the Space Shuttle or the ISS, they must first do a radar check for anything readable, and constant visual checks as well for any wayward junk.
The first and most arduous of tasks is, of course, the piloting of the Space Shuttles. The Space Shuttles are the current method of transferring people and supplies back and forth to the ISS, as well as launching satellites and other space missions, like repairing the Hubble Telescope. However, the two Shuttles are due to be taken out of commission in late 2010, with their replacements due near 2015, leaving the astronauts to hitch-hike along with the cosmonauts, and soon the Chinese or Japanese to get to the ISS for five years. Maybe Sir Richard Branson, owner of the Virgin and Virgin Galactic empires, will offer NASA a few well needed rides up to the ISS, where they could carry out the jobs that they have been training all of their lives for.
Eventually, astronauts will have a smaller, space-oriented vehicle, which will be parked at the ISS, and could be used for performing repairs on the Hubble Telescope, other satellites, and aid in any emergency situations. But until the ISS is up and running, astronauts have a lot of work to do in making it a reality. New modules are delivered to the ISS via the Space Shuttles, since they have larger cargo bays than the Soyuz rockets the cosmonauts use to get up above the wild blue yonder. And the telescoping Canada-Arm, a robotic-like articulated mechanical arm that can be used to place satellites into orbit or tighten bolts, perform welding and other specialized tasks that would be far too dangerous for astronauts to carry out.
Astronauts have to perform science experiments, social and engineering experiments, as well as trying out new technologies for the ISS. The ISS does a lot more than house a few astronauts and cosmonauts, it is the salvation of mankind. The thinking is that, once complete, the ISS will be big enough for a large contingency of healthy, smart people to leave the Universe as we know it, and venture into the unknown, looking for new planets to live on and destroy. Astronauts will be at the helms of the ISS as it takes off on it's five year mission, to seek out new planets and new civilizations, to boldly go where no astronaut has gone before