To hear complaints of "cost overruns" for this mission, knowing well the role that the upper NASA management played in adding to those costs is grating on the ear, I must say. I suggest to read these links for details of the Dawn mission from Mark Sykes, the director of the Planetary Science Institute, writing to the House Science Committee Chair on Friday: http://www.spaceref.com/news/viewsr.html?pid=19838 and his interview with the Planetary Society: http://www.planetary.org/blog/article/00000475/ As for technical problems, yes there were things that were critical to address, but the Dawn Independent Assessment Team, who gave their report to NASA in late January, stated that the Dawn mission was no different in their mission development from any other successful space mission in their late stage of development and they gave a recommendation to finish the project and launch. Another example of the misinformation of the Dawn problems are the much-talked about xenon tanks, which were, in fact, tested at twice their designed conditions when they failed, and on the day of the cancellation, NASA had a letter from the project (at JPL) stating that all xenon tank problems were solved. Please remember that all Dawn instruments were built and more than halfway through the spacecraft integration at the time of the cancellation, so the Dawn spacecraft was ~95% constructed. And not only dollars were spent, but significant amount of euros too, because two of the three Dawn instruments were European, instruments paid for by NASA's international partners: the German Aerospace Agency and Italian Space Agency.