BACKGROUND

On July 4, 2005, the Deep Impact mission achieved an incredibly complex experiment in space, excavating beneath the surface of a comet to reveal its interior.  Traveling at 23,000 miles per hour, the larger "flyby" spacecraft released a smaller "impactor" spacecraft into the path of comet Tempel 1.  Audiences around the world witnessed the brilliant release of dust upon impact 83 million miles from Earth, as dramatic images from both spacecraft were shown in near real-time on NASA TV and over the Internet.

This image was taken by Deep Impact's high resolution camera, which will be used for the EPOXI observations.  It shows comet Tempel 1 in 2005, fifty minutes after collision with the impactor.

While the impactor was vaporized, the flyby spacecraft continued on.  Scientists gained a tremendous amount of knowledge as a result of the encounter, but will learn even more when the Stardust spacecraft revisits comet Temple 1 in 2011 in its new task as Stardust-NExT (New Exploration of Tempel 1). 

EPOCh SCIENCE OBJECTIVES

The EPOCh observation, which begins on January 26, 2008, and continues until about the end of May 2008, will:

• Investigate planets known to orbit 3-6 distant stars and to search those stars for previously undiscovered planets
• Search for evidence of rings and moons associated with the known giant planets of the targeted stars
• Observe the Earth at both visible and infrared wavelengths to help scientists understand what an Earth-like planet might look like if it were orbiting a distant star

Using the Deep Impact high-resolution instrument (HRI), EPOCh will use the transit method to learn more about planets that are known to orbit these stars and to search for clues that other planets might be orbiting the same stars.  Planets as small as three Earth masses may be detected this way.  EPOCh's Earth observations will help in making computer models of planetary images that are not so Earth-like and will guide future efforts to detect and study extrasolar planets directly.

EPOCh offers the advantages of a telescope in space where it can watch a single star nearly continuously for weeks, far surpassing what can be learned from a telescope on the ground where atmosphere limits observation capabilities.

DIXI SCIENCE OBJECTIVES

DIXI continues Deep Impact's comet study by flying past comet Hartley 2 on October 11, 2010. A primary focus of the investigation is to compare Hartley 2 with comets observed by other spacecraft missions to help determine which cometary features are primordial and which are the result of subsequent evolutionary processes.

DIXI's objectives are to:

• Search for outbursts of gas from the comet's surface and produce spectral maps if they are found; track the outburst as the comet rotates; correlate outbursts with surface feature
• Obtain infrared spectral maps of gasses in the innermost coma; investigate the distribution of dust and gas in the coma
• Search for frozen volatiles on the surface of the comet
• Produce broad band images of the comet and a model of its shape
• Map the brightness and color variations of the surface; locate topographical features that reveal what processes formed the comet; compare the distribution of various crater sizes with craters on other comets, asteroids and moons
• Map the temperature of the surface to assess the thermal conductivity of the interior and the migration of subsurface volatiles

MISSION MANAGEMENT

Michael A'Hearn of the University of Maryland, College Park, is EPOXI's principal investigator and the leader of the DIXI science team. L. Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, MD, is EPOXI's deputy principal investigator and leads the EPOCh investigation. NASA's Jet Propulsion Laboratory, Pasadena, CA, manages the project. Ball Aerospace & Technologies Corporation, Boulder, CO, built the spacecraft.

A Discovery Mission of Opportunity is not a complete Discovery Mission, but is part of a larger mission or an extension of completed mission. It gives the U.S. scientific community the chance to participate in non-NASA missions by providing funding for a science instrument, hardware components of a science instrument, or expertise in critical areas of a mission. It also offers the opportunity to re-purpose an existing NASA spacecraft that has completed its prime mission.

For more information, please visit the EPOXI homepage.