EPOXI mission sets up for comet flyby

The maneuver refined the spacecraft's orbit, setting the stage for its flyby of comet Hartley 2 on Nov. 4. Time of closest approach to the comet was expected to be about 14:02 UTC.

The trajectory correction maneuver began at 18:00 UTC, when the spacecraft fired its engines for 60 seconds, changing the spacecraft's velocity by 1.53 meters per second (3.4 mph).

"We are about 23 million miles and 36 days away from our comet," said EPOXI project manager Tim Larson of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "I can't wait to see what Hartley 2 looks like."

On Nov. 4, the spacecraft will fly past the comet at a distance of about 700 kilometers (435 miles). It will be only the fifth time in history that a spacecraft has been close enough to image a comet's nucleus, and the first time in history that two comets have been imaged with the same instruments and same spatial resolution.

This EPOXI mission image of comet 103P/Hartley 2 was taken 40 days from Encounter (E-40d) using the Medium Resolution Instrument (MRI) and a clear filter. Science Team member Dr. Dennis Wellnitz combined seven successive one-minute exposures to make this single image. The mid-exposure time was 2010/09/25 13:29:31 UTC. The comet was 1.15 AU from the Sun and 0.27 AU (41 million km) from the spacecraft. The Sun is straight "down" from the comet and celestial north is to the lower right. Credit: NASA/JPL/UMD




Negative of the same image which makes it a little easier to see the faint coma around the comet. Credit: NASA/JPL/UMD

"We are imaging the comet every day, and Hartley 2 is proving to be a worthy target for exploration," said Mike A'Hearn, EPOXI principal investigator from 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 will continue to be referred to as "Deep Impact."

Source: Jet Propulsion Laboratory
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