page_title: EPOXI
section_title: Comet flyby
hierarchical_section_title: EPOXI / Mission / Comet flyby
caption_attribution_description: English: Animation of Deep Impact's trajectory from 12 January 2005 to 1 September 2010 &#160;&#160;&#160;&#160;&#160;&#160;Deep Impact&#160;· &#160;&#160;&#160;&#160;&#160;&#160;Tempel 1&#160;· &#160;&#160;&#160;&#160;&#160;&#160;Earth&#160;· &#160;&#160;&#160;&#160;&#160;&#160;103P/Hartley
context_page_description: EPOXI is 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 and Extrasolar Planet Observation and Characterization. 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 gravity assists 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.
context_section_description: The spacecraft used Earth's gravity for the second gravity assist in December 2008 and made two distant flybys of Earth in June and December 2009. On May 30, 2010 it successfully fired its engines for an 11.3 second trajectory correction maneuver, for a velocity change (Δv) of 0.1 meters per second (0.22 mph), in preparation for the third Earth flyby on June 27. Observations of 103P/Hartley began on September 5 and ended November 25, 2010. For a diagram of the EPOXI solar orbits see here.
  The mission's closest approach to 103P/Hartley occurred at 10 am EDT on 4 November 2010, passing to within 694 kilometers (431 mi) of this small comet. The flyby speed was 12.3 km/s. The spacecraft employed the same suite of three science instruments—two telescopes and an infrared spectrometer—that the Deep Impact spacecraft used during its prime mission to guide an impactor into comet Tempel 1 in July 2005 and observe the results.
  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.
caption: Animation of Deep Impact's trajectory from 12 January 2005 to 8 August 2013
      Deep Impact 1   Tempel 1   Earth   103P/Hartley