  On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its
goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on
the nucleus and ejecting material into the coma of the comet. NASA's
Submillimeter Wave Astronomy Satellite (SWAS) observed the 1(10)-1(01)
ortho-water ground-state rotational transition in comet 9P/Tempel 1 before,
during, and after the impact. No excess emission from the impact was detected
by SWAS and we derive an upper limit of 1.8e7 kg on the water ice evaporated by
the impact. However, the water production rate of the comet showed large
natural variations of more than a factor of three during the weeks before and
after the impact. Episodes of increased activity with Q(H2O)~1e28 molecule/s
alternated with periods with low outgassing (Q(H2O)<~5e27 molecule/s). We
estimate that 9P/Tempel 1 vaporized a total of N~4.5e34 water molecules (~1.3e9
kg) during June-September 2005. Our observations indicate that only a small
fraction of the nucleus of Tempel 1 appears to be covered with active areas.
Water vapor is expected to emanate predominantly from topographic features
periodically facing the Sun as the comet rotates. We calculate that appreciable
asymmetries of these features could lead to a spin-down or spin-up of the
nucleus at observable rates.
