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Project Progress

The Deep Impact mission is the first planetary mission to carry out direct experimentation on a cometary body by delivering a 360-kg impactor to comet 9P/Tempel 1 at 10.2 km/s on UT July 4, 2005. UHNAI team members were closely involved in the world-wide effort of ground- and Earth-orbital observations to characterize the target nucleus pre-impact and to observe throughout the period of Encounter. The specific accomplishments during year 7 for this mission included:

• 6 nights of telescope time on the Univ. of Hawaii 2.2m telescope to observe the development and evolution of the dust coma. Beginning in Nov. 2004 observations revealed that the outgassing had begun the development of the coma, and by January 2005, jets were observed. Deep composite images are enabling the team to apply dust-dynamical models to the images to understand the grain size distributions in the coma, the grain ejection velocities and when the activity began. Deep searches for large particles left in a dust trail from the previous apparition were negative, suggesting the absence of small particles.
• 3 half nights were awarded on the Keck 10-m telescope for low resolution spectroscopy to observe the onset of sublimation and measure the production rates of gas species (CN, C₂, C₃, NH₂, OH). Simultaneous observations of the dust indicated that the coma grew redder as the activity increased, consistent with the increased outflow of gases being able to lift larger particles off the nucleus.
• Astrometric (position) measurements were made for the entire 8 year database of observations that we had for the comet and contributed to the orbit solutions used to navigate to the comet. Of the total world-wide observations, only 951 were high enough quality to be used in the orbit solution, and 374 of these were from Mauna Kea.

In addition to coordinating the world observing encounter effort through multiple video conferencing (with up to 32 sites simultaneously), and near real-time accessibility of observations from all sources via the web, UH NAI team members played a leading science role at encounter by leading several observing efforts and collaborating on several others:

• Dust evolution after impact (utilizing the Cerro Tololo interamerican observatory 4m, 1.5m, 0.9m and Schmidt telescopes, along with the CFHT 3.6m telescope on Mauna Kea): goal to assess whether the dust characteristics change post-impact.
• Gaseous isotope ratios using high resolution spectroscopy on Keck to examine fractionation processes in comet formation.
• Gas and dust volatile composition — using the Spitzer space infrared telescope to watch the evolution of organic species post impact.
• Light curve evolution — observations using the Hubble Space Telescope and the Lowell Observatory 72-inch telescope showed a complex light curve. We are analyzing this in the context of impact cratering dynamics.

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