* Astronomy

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RE: Deep Impact

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At Gemini the night of July 4th, 2005 was filled with fireworks, both earthly and celestial. In support of NASAs Deep Impact (DI) mission two teams of scientists used the Gemini mid-infrared instruments MICHELLE and T-ReCS to acquire imaging and spectroscopic observations of Comet Tempel 1 throughout the impact event. At Gemini South a team led by David Osip (Carnegie Inst.) and James De Buizer (Gemini) used T-ReCS to image the impact and the resulting dust plume.

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NASA on Tuesday gave new assignments to two robotic space travellers that have already completed the missions for which they were designed: the comet-watching Deep Impact spacecraft, and the comet-sampling Stardust probe.
The Deep Impact spacecraft, which flew by Comet Tempel 1 after sending an impactor in its path in 2005, is due to fly past yet another comet in 2008 and observe stars known to have planets circling them.
Stardust, meanwhile, will be sent to pay its own visit to Comet Tempel 1 in 2011. The Stardust spacecraft dropped off a sample capsule containing comet dust and interstellar samples as it flew past Earth last year, and has essentially been in an interplanetary holding pattern ever since.

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EPOXI mission

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DIXI mission

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Water lines detected

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RE: Deep Impact

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Title: Radio observations of comet 9P/Tempel 1 with the Australia Telescope facilities during the Deep Impact encounter
Authors: P. A. Jones, J. M. Sarkissian, M. G. Burton, M. A. Voronkov, M. D. Filipovic

Researchers present radio observations of comet 9P/Tempel 1 associated with the Deep Impact spacecraft collision of 2005 July 4. Weak 18-cm OH emission was detected with the Parkes 64-m telescope, in data averaged over July 4 to 6, at a level of 12 ± 3 mJy km/s, corresponding to OH production rate 2.8 x 1028 molecules/second (Despois et al. inversion model, or 1.0 x 1028/s for the Schleicher & A'Hearn model).
They did not detect the HCN 1-0 line with the Mopra 22-m telescope over the period July 2 to 6. The 3 sigma limit of 0.06 K km/s for HCN on July 4 after the impact gives the limit to the HCN production rate of < 1.8 x 1025/s.
They did not detect the HCN 1-0 line, 6.7 GHz CH_3OH line or 3.4-mm continuum with the Australia Telescope Compact Array (ATCA) on July 4, giving further limits on any small-scale structure due to an outburst. The 3 sigma limit on HCN emission of 2.5 K km/s from the ATCA around impact corresponds to limit < 4 x 1029 HCN molecules released by the impact.

Spectrum of the OH 1667-MHz line in comet 9P/Tempel 1, integrated over 3 days of Parkes observations, 2005 July 4 – 6. The spectra have been combined after correcting for the geocentric velocity of the comet, so the velocity scale is relative to the comet ephemeris.

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Scientists for Deep Impact, the University of Maryland-led NASA mission that made history when it smashed into a comet on July 4th, 2005, have added another first to their growing list: the first finding of water ice on the surface of a comet.

By analysing data and images taken prior to impact, Deep Impact scientists have detected water ice in three small areas on the surface of comet Tempel 1. This is the first time ice has been detected on the nucleus, or solid body, of a comet. The findings are published today in the online version of the journal Science.

"These results show that there is ice on the surface, but not very much and definitely not enough to account for the water we see in the out-gassed material that is in the coma [the cloud of gas and dust that surrounds the comet" - Jessica Sunshine, lead author, Science Applications International Corporation.

"These new findings are significant because they show that our technique is effective in finding ice when it is on the surface and that we can therefore firmly conclude that most of the water vapour that escapes from comets is contained in ice particles found below the surface" - Michael A'Hearn, University of Maryland, Deep Impact Principal Investigator.

Through observations of ice grains and water vapour in the coma of comets, scientists have long known that "dirty snowballs," as comets are sometimes described, must indeed contain substantial amounts of water ice. However, prior to Deep Impact they didn't have any knowledge about how such ice was distributed between the surface, subsurface and inner core of a comet's nucleus.
In the Science article, the authors say that prior to Deep Impact there existed few observations of nuclei not obscured by the coma. Among previous cometary missions, the most notable of such observations was the Deep Space-1 mission to comet Borrelly, which searched unsuccessfully for evidence of water ice and other volatiles on that comet's surface. Limited ground based observations of possibly bare cometary nuclei have also failed to find clear evidence of surface ice.
The fact that the Deep Impact team found water on the surface, but only in a few scattered places, all but eliminates the possibility that there is a lot of undetectable surface ice "just hiding in the surface darkness".

The surface ice that the team detected was not located where the impact later occurred. This means that the water ice and water vapour the team already had found in analyses of material ejected by the July 4 impact must have come from ice located close to, but not on, the surface of the comet.
As a comet approaches the Sun, it releases gas and dust forming a cloud (coma) that obscures the nucleus from view unless spacecraft can get very close. Deep Impact did just that. The Deep Impact science team used four types of data in their search for ice on the mostly coal black surface of Tempel 1.

First, images from Deep Impacts high resolution and medium resolution instruments (the HRI and MRI) showed three small regions that were about 30 percent brighter than surrounding areas. After scaling the images to the average brightness value of the nucleus, these three discrete areas on the nucleus where found to be brighter in the ultraviolet and darker in the near-infrared, a combination that is consistent with water ice. In addition, Sunshine's analysis of the spectra of light emitted and absorbed in those regions showed the distinctive spectral signature of water ice. The combination of the relative colours and the spectral signature make a powerful case that there is water ice at these specific locations on Tempel 1.

Using visual images and spectral mapping of the impact side of the surface of Tempel 1, the team found that the patches of surface ice represented only 0.5 percent of the total observed surface.
Team member Olivier Groussin, a University of Maryland research scientist, made a temperature map and combined it with the colour map to show that two of the three ice patches regions were in colder regions of the nucleus. Stereo images show the largest area of ice to be a depression 80 meters below surrounding areas.

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Deep Impact, the University of Maryland-led NASA mission that made history and worldwide headlines when it smashed into a comet this past July 4th, has won the Space Frontier Foundation's Vision to Reality award.

"Deep Impact was selected because it represents the best accomplishment of the year in turning the vision of true space exploration and the gathering of scientific knowledge, into reality.
Furthermore, (the University of Maryland's mission leadership) demonstrates that American institutions other than NASA are adept at conducting challenging space missions" - Jeff Krukin, executive director of the Space Frontier Foundation.

The award was presented to mission leader and principal investigator Michael A'Hearn of the University of Maryland at the foundation's annual conference in Los Angeles, California, October 21-23, 2005.

"This award is a really great tribute to the large team that put in a tremendous amount of effort to make the mission happen. The Space Frontier Foundation is an advocate for activities in space that break the paradigm and we are proud to be put in that class" - Michael A'Hearn , University Professor in the department of astronomy at Maryland.

Deep Impact's excavation of a comet drew worldwide attention and was widely acclaimed as a tremendous scientific and engineering success. The mission was, by almost any measure, NASA's most widely followed unmanned mission ever, and one of its most popular of all time. NASA reported that there were more than a billion hits on mission web sites around the time of impact.

Deep Impact is one of 10 missions selected to date as part of NASA's Discovery Program. According to NASA, the Discovery Program "gives scientists the opportunity to dig deep into their imaginations and find innovative ways to unlock the mysteries of the solar system. It represents a breakthrough in the way NASA explores space, with lower-cost, highly focused planetary science investigations designed to enhance our understanding of the solar system".

Eight of the 10 Discovery missions have launched. Of these, the Deep Impact, NEAR, Pathfinder and Prospector missions have been successfully completed. Stardust and Messenger have not yet completed their missions. One, CONTOUR was lost shortly after launch. Another, Genesis crashed on its return to Earth when its parachutes failed to open. However, Genesis is still considered a tremendous achievement by scientists, because most of the mission's samples of solar wind particles were recovered and are being analysed.

Maryland Deep Impact team - Spring '04 - (from left, front row) Administrative Assistant Linda Diamond, Graduate Assistant Donna Pierce, Associate Research Scientist Rosemary Killen, Faculty Research Assistant Anne Raugh, Associate Research Faculty Elizabeth Warner, Faculty Research Assistant Stephanie McLaughlin and Associate Research Professor Lucy McFadden; (from left, back row) Professor Mike A'Hearn, Research Associate Tony Farnham, Undergraduate Student Tim Cline, Senior Research Scientist Casey Lisse, Research Associate Ed Grayzeck and Postdoc Olivier Groussin.

Deep Impact differed from most Discovery missions in that it was led by a university not directly affiliated with a NASA Centre. According to the Space Frontier Foundation and other observers, Deep Impact also stands out because of principal investigator A'Hearn's hands-on, detailed leadership of almost all aspects of the mission, and because of the breadth of involvement in the mission by other University of Maryland scientists. More than a dozen scientists, staff and students in the university's department of astronomy were involved in the mission, together with a science team assembled from 9 other institutions around the world.

In addition to A'Hearn, University of Maryland participants included research scientist Lucy McFadden, a science team member and director of education and public outreach for the mission; Dennis Wellnitz, a faculty research scientist who managed instrument development and performance; Stephanie McLauglin, a faculty research assistant who coordinated the mission's Small Telescope Science Program; Carey (Casey) Lisse, a senior research scientist in the astronomy department during much of the mission's seven years and now with the John Hopkins Applied Physics Laboratory, who led the effort to extract views of the nucleus from spacecraft images; Elizabeth Warner, director of the University of Maryland's campus observatory and liaison to the amateur astronomy community for the mission; Olivier Groussin, a research associate who was an expert on thermal models of the nucleus of Comet Tempel 1; research associate Tony Farnham; and post doctoral researcher Lori Feaga.

"Maryland graduate students involved in Deep Impact worked on thesis topics that helped us to interpret the mission results. And undergraduates from the university's College Park Scholars program also worked with the Deep Impact team over the past six years contributing to the mission's web pages and as research assistants" - Lucy McFadden.

Deep Impact was carried out as a partnership among the University of Maryland, NASA's Jet Propulsion Laboratory (JPL), and Ball Aerospace & Technologies Corporation. The university, through principal investigator A'Hearn, was responsible for the entire mission and directly managed the scientific effort, education and outreach, and the development of the instruments on the spacecraft. The Deep Impact science team has submitted a proposal for an extended mission for the mission's flyby spacecraft to visit another comet. This proposal will be considered under the next Announcement of Opportunity for the Discovery Program.

According to its web site, the Space Frontier Foundation is an organization "dedicated to the human settlement of space in our lifetime." Its stated purpose is to "unleash the power of free enterprise and lead a united humanity permanently into the Solar System" by "transforming space from a government-owned program into a dynamic and inclusive frontier open to all people."

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