Lunar and Planetary Institute
Lunar and Planetary Institute



NASA Mission Successfully Flies by Comet Hartley 2

November 4, 2010

Comet Hartley 2 can be seen in glorious detail in this image from NASA’s EPOXI mission. It was taken as the spacecraft flew by around 6:59 a.m. PDT (9:59 a.m. EDT), from a distance of about 700 kilometers (435 miles). The comet’s nucleus, or main body, is approximately 0.4 kilometers (0.25 miles) at the “neck,” or most narrow portion. Jets can be seen streaming out of the nucleus. The mission’s Medium-Resolution Instrument was used to capture this view. NASA’s EPOXI mission successfully flew by Comet Hartley 2 at about 7:00 a.m. PDT (10:00 a.m. EDT) today, and the spacecraft has begun returning images. Hartley 2 is the fifth comet nucleus visited by a spacecraft.

Scientists and mission controllers are currently viewing never-before-seen images of Hartley 2 appearing on their computer terminal screens.

“The mission team and scientists have worked hard for this day,” said Tim Larson, EPOXI project manager at NASA’s Jet Propulsion Laboratory. “It’s good to see Hartley 2 up close.”

Mission navigators are working to determine the spacecraft’s closest approach distance. Preliminary estimates place the spacecraft close to the planned-for 700 kilometers (435 miles). Eight minutes after closest approach, at 6:59:47 a.m. PDT (9:59:47 a.m. EDT), the spacecraft’s high-gain antenna was pointed at Earth and began downlinking vital spacecraft health and other engineering data stored on the spacecraft’s onboard computer during the encounter. About 20 minutes later, the first images of the encounter made the 37-million-kilometer (23-million-mile) trip from the spacecraft to NASA’s Deep Space Network antennas in Goldstone, California, appearing moments later on the mission’s computer screens.

“We are all holding our breath to see what discoveries await us in the observations near closest approach,” said EPOXI principal investigator Michael A’Hearn of the University of Maryland, College Park.

EPOXI is an extended mission that utilizes the already “in-flight” Deep Impact spacecraft to explore distinct celestial targets of opportunity. The name EPOXI itself is a combination of the names for the two extended mission components:  the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of Comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft has retained the name “Deep Impact.”

For more information, visit

EPOXI:  Encounter with Comet Hartley 2

EPOXI:  Two Intriguing Investigations — One Flight-Proven Spacecraft

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Last updated November 4, 2010