In July NASA announced extended missions for the Deep Impact and Stardust spacecraft. Stardust is on its way to a 2011 rendezvous with the comet that Deep Impact blasted, Tempel 1, while Deep Impact was being sent onto a December 5, 2008 flyby of comet Boethin. Unfortunately, according to an update posted to the mission website by Principal Investigator Mike A'Hearn, "heroic efforts" on the part of ground-based astronomers have failed to recover comet Boethin. In other words, we know it's out there, and we know approximately where it is based upon past observations, but we can't actually spot it, even with the best telescopes; it's just too dim. Even though the planned flyby is more than a year away, we need to know now where Boethin is, because on December 31 of this year Deep Impact is going to fly by Earth for a gravity assist to set up the encounter. The mission can't plan the gravity assist properly without precise, up-to-date knowledge of the position of Boethin. So the team had to go to a backup target, a comet called 103P/Hartley 2, whose orbit is much better known than Boethin's.
The problem with Hartley 2 is that it will take Deep Impact two years longer -- and, therefore, more money -- to get there; and you should all now be familiar with the situation facing missions that go to NASA asking for more money. NASA has not promised the necessary additional two years of funding, but they did, at least, authorize the mission to set up the December 31 encounter for the Hartley 2 flyby. The maneuver to set up the flyby was executed on November 1, so Deep Impact is now committed to a Hartley 2 flyby on October 11, 2010, whether or not we choose to use Deep Impact to study the comet.