Asteroid studies are conducted robotically. There is not much in the way of human space travel, and due to the expense of same, won't be for a while. NASA's new GWB-inspired focus on a return to the Moon and missions to Mars are encouraging. My view is, a permanent human presence on the Moon would be the best politically possible outcome -- plan for Mars, and settle for the Moon.
Anyway, in the meanwhile, the only things to be done in space are those done with robots, and in that category I include the Hubble Space Telescope, the Mars probes, the upcoming planned probe to Pluto, and of course the various missions to various comets and asteroids.
Anything big enough to end civilization with an impact on the Earth remains unknown. And that's probably how it would be -- unknown until its far too late to do anything about it.
BTW:
It's called Apophis. It's 390m wide. And it could hit Earth in 31 years time [Asteroid]
The Guardian (UK) | December 7, 2005 | by Alok Jha
Posted on 12/06/2005 6:59:40 PM PST by aculeus
http://www.freerepublic.com/focus/f-news/1535383/posts
Astronauts push for strategies, spacecraft to prevent cosmic collision
Flagstaff Arizona Sun | 11/06/2005 | Marcia Dunn
Posted on 11/06/2005 5:53:40 PM PST by Graybeard58
http://www.freerepublic.com/focus/f-chat/1517000/posts
Scientist: Asteroid May Hit Earth in 2029
Yahoo/AP | 12/23/04 | JOHN ANTCZAK
Posted on 12/23/2004 8:24:16 PM PST by hole_n_one
http://www.freerepublic.com/focus/news/1307719/posts
Not exclusively though. As there have been some rather notable asteroid discoveries by amateur astronomers, using amateur equipment. Not to mention comet discoveries achieved by amateurs.