Product Code Database
EPOXI was a compilation of NASA Discovery program missions led by the University of Maryland and principal investigator Michael A'Hearn, with co-operation from the Jet Propulsion Laboratory and Ball Aerospace. EPOXI uses the Deep Impact spacecraft in a campaign consisting of two missions: the Deep Impact Extended Investigation (DIXI) and Extrasolar Planet Observation and Characterization (EPOCh). DIXI aimed to send the Deep Impact spacecraft on a flyby of another comet, after its primary mission was completed in July 2005, while EPOCh saw the spacecraft's photographic instruments as a space observatory, studying extrasolar planets.
DIXI successfully sent the Deep Impact spacecraft on a flyby of comet Hartley 2 on November 4, 2010, revealing a "hyperactive, small and feisty" comet, after three from Earth in December 2007, December 2008 and June 2010. The DIXI mission was not without problems, however; the spacecraft had initially been targeted for a December 5, 2008 flyby of comet Boethin, though, the comet could not be located, and was later declared a lost comet, prompting mission planners to reorganize a flyby of an alternative target, Hartley 2. After its flyby of Hartley 2, the spacecraft was also set to make a close flyby of the Apollo asteroid (163249) 2002 GT in 2020. The mission ended after contact with the spacecraft was suddenly lost in August 2013 and attempts to re-establish contact in the following month had failed. NASA calls off search for lost Deep Impact comet probe - Australian Broadcasting Corporation - Retrieved September 21, 2013. Mission scientists theorized that a Y2K-like problem had plagued the spacecraft's software.
The initial plan was for a December 5, 2008 flyby of Comet Boethin, with the spacecraft coming within . The spacecraft did not carry a second impactor to collide with the comet and would observe the comet to compare it to various characteristics found on 9P/Tempel. A'Hearn, the Deep Impact team leader reflected on the upcoming project at that time: "We propose to direct the spacecraft for a flyby of Comet Boethin to investigate whether the results found at Comet Tempel 1 are unique or are also found on other comets." He explained that the mission would provide only about half of the information collected during the collision with Tempel 1 but at a fraction of the cost. (EPOXI's low mission cost of $40 million is achieved by reusing the existing Deep Impact spacecraft.) Deep Impact would use its spectrometer to study the comet's surface composition and its telescopes for viewing the surface features. However, as the Earth gravity assist approached, astronomers were unable to locate Comet Boethin, which is too faint to be observed. Consequently, its orbit could not be calculated with sufficient precision to permit a flyby. Instead, the team decided to send Deep Impact to comet 103P/Hartley requiring an extra two years. NASA approved the additional funding required and retargeted the spacecraft. EPOXI Mission Status , NASA/University of Maryland, December 2, 2007. Mission controllers at the Jet Propulsion Laboratory began redirecting EPOXI on November 1, 2007. They commanded the spacecraft to perform a three-minute rocket burn that changed the spacecraft's velocity. EPOXI's new trajectory set the stage for three Earth flybys, the first on December 31, 2007. This placed the spacecraft into an orbital "holding pattern" so that it could encounter comet 103P/Hartley in 2010.
"It's exciting that we can send the Deep Impact spacecraft on a new mission that combines two totally independent science investigations, both of which can help us better understand how solar systems form and evolve," said in December 2007 Deep Impact leader and University of Maryland astronomer Michael A'Hearn who is principal investigator for both the overall EPOXI mission and its DIXI component.
In June 2009, Deep Impact and Other Spacecraft Find Clear Evidence of Water on Moon: Thin layer of surface 'dew' appears to form, then dissipate each day EPOXI's spectrometer scanned the Moon on its way to Hartley, and discovered traces of "water or hydroxyl", confirming a Moon Mineralogy Mapper observation — a discovery announced in late September, 2009.
| +Planetary systems observed | |
| 486 | b |
| 33.48 | b |
| 1010 | b |
| 1300 | TrES-3b |
| 727 | b |
| 718 | TrES-2b |
| 1044 | b |
Early results of the observations show that the comet is powered by dry ice, not water vapor as was previously thought. The images were clear enough for scientists to link jets of dust and gas with specific surface features.
"When comet Boethin could not be located, we went to our backup, which is every bit as interesting but about two years farther down the road," said Tom Duxbury, EPOXI project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "Hartley 2 is scientifically just as interesting as comet Boethin because both have relatively small, active nuclei," said Michael A'Hearn, principal investigator for EPOXI at the University of Maryland, College Park.
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