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Planetary News: Deep Impact (2005)

Deep Impact Sets a New Course as Tempel 1 Returns to Normal

By Emily Lakdawalla
July 20, 2005

With its mission at Tempel 1 over, the Deep Impact spacecraft has altered its course in order to allow a future mission at another comet. This morning's trajectory correction maneuver has placed Deep Impact on a course that will result in an Earth flyby in December of 2007. A statement from NASA Headquarters says that "The maneuver allows NASA to preserve options for future use of the spacecraft." The statement does not mention the likely target, comet Boethin, in an encounter that would take place in 2008.

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The reason that a target is not mentioned is because NASA has not yet allotted funding for an extended mission for Deep Impact. In fact, funding for such a mission is not guaranteed, said Andy Dantzler, Director of the Science Mission Directorate of the NASA's Solar System Division. "All proposals for use of the Deep Impact spacecraft will be evaluated for science merit and feasibility along with all submitted proposals for [Discovery Program] Missions of Opportunity," he said. "The spacecraft is being offered as is. Proposers must include mission management and spacecraft operations in the total proposed funding."

Following is the language of the 2004 NASA Discovery Program "Mission of Opportunity" Announcement of Opportunity (AO) regarding the use of Discovery Program funds for extended missions. Deep Impact scientists will have to propose their extended mission to the next Discovery Program AO.

5.12 Specific Requirements and Constraints for Mission of Opportunity Investigations

5.12.1 Overview

By supporting U.S. participation in MO investigations, NASA seeks to allow the U.S. scientific community to conduct a science investigation of interest to OSS [Office of Space Science] as part of missions sponsored by non-OSS organizations and/or using existing flight hardware for missions that have completed their prime science missions. Such "parent" non-OSS missions may be sponsored by non-U.S. governments, other U.S. agencies, NASA organizations other than OSS, the U.S. military (only if the satellite is not planned for weapons testing), or private sector organizations, and all are equally qualified. Mission extensions and proposals for new science missions that utilize existing in-flight OSS spacecraft are also allowed in this opportunity. The total cost to NASA for a Discovery MO investigation, including all costs for Deep Space Mission System (DSMS) support and/or Navigation and Ancillary Information Facility (NAIF) services, through this AO is limited to $35M (FY 2004 dollars).

5.12.3 Extended Science Missions

Approved NASA SSE [Solar System Exploration] missions nearing the end of their Prime or Extended Missions may propose a mission extension through this AO. The extended science mission being proposed must commence no later than December 31, 2005. A proposal for an extended science mission must include all costs to NASA for the extension of the mission including mission operations, DSMS costs, any proposed data analysis, and adequate resources for archiving new results.

Such a move is unusual to say the least. "I don't think there's any precedent for it," said Planetary Society Director of Projects Bruce Betts, who was Program Scientist for various NASA missions. "Discovery Program Missions of Opportunity usually are used for people to propose for funding for an instrument to fly on a foreign spacecraft. Never before has it actually been used to fly a spacecraft. This time, it really is a 'mission' of opportunity."

Betts added that, in fact, only two Missions of Opportunity have ever been funded, ASPERA on ESA's Mars Express, currently in orbit, and the Moon Mineralogy Mapper on the Indian Space Research Organization's lunar orbiter Chandraayan-1, scheduled for launch in 2007. In addition, an experiment to place wind sensors and seismometers on the French-led NetLander was funded, but discontinued with the cancellation of that mission.

It took a large and complex team of scientists and engineers from the University of Maryland, the Jet Propulsion Laboratory, and elsewhere to guide Deep Impact past Tempel 1. If they want to fly the spacecraft by another comet, they will have to re-propose to the Discovery program, competing against all other proposals for the limited pot of money up for grabs in the 2005 Missions of Opportunity.

Tempel 1 Returns to Normal

Meanwhile, Comet Tempel 1 has quickly returned to a normal state, only a few weeks after Deep Impact smashed it with a 370-pound ball. Astronomers around the world have continued to monitor the comet and have seen its behavior grow quiet.

At the European Southern Observatory in Chile, astronomer Hermann Boehnhardt headed a campaign to use all seven of the ESO telescopes to watch Tempel 1, at every wavelength of light that was not blocked by the Earth's atmosphere. "For a number of days after the impact you have this ejecta cloud going to the southwest, and this disappeared after three or four days in the coma again, because the dust was blown off," he said.

Based upon the observations performed at ESO, Boehnhardt believes that Deep Impact had no lasting effect on Tempel 1. "The comet never went away from its normal state -- its [formerly] active regions were still active during the impact of course, and you can see the active regions shining through the ejecta cloud. It looks like the ejecta cloud was on top of something that was there all the time, before and after."

These conclusions represent just the beginning of the scientific results of the Tempel 1 observation campaign. The first peer-reviewed papers to present new results from Deep Impact's encounter with Tempel 1 are now being written and submitted to Science magazine. Members of the Deep Impact science team and the international observers hope to see those first results in print by the time of the annual meeting of the Division of Planetary Sciences of the American Astronomical Society to be held in Cambridge, England, in September. The Planetary Society will be there for the latest news on this and other developing stories in planetary science.