SWAN observations of 9P/Tempel 1 around the Deep Impact event

The SWAN instrument observed the coma of Comet 9P/Tempel 1 at Lyman alpha around the Deep Impact event. From these observations, a water production rate profile for 3 weeks after the impact was derived. The comet could not be identified in images taken before the impact because of the relatively low production rates. The most important feature of the profile is that the production rate increases by about a factor of two more than a week after the impact. This is too late to be directly caused by the impact plume itself. Although it is not impossible that the impact triggered a resurfacing event, the comet is known to show sudden outburts, and the elevated production rate is similar to what has been reported on previous apparitions.