Deep Impact on Track for Comet Encounter

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NASA’s Deep Impact spacecraft is set to pass within 700 kilometers of Comet Hartley 2 on Nov. 4.

The flyby should help scientists learn more about comet structure and evolution, as well as the early days of the solar system, researchers said. “This is going to give us the most extensive observation of a comet to date,” Tim Larson of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., told reporters Oct. 26. Larson is project manager of Deep Impact’s extended mission, which NASA calls EPOXI.

Hartley 2 completes its long, looping sojourn around the sun every 6.5 years. It was discovered in 1986 by astronomer Malcolm Hartley and made its closest approach to Earth in 24 years on Oct. 20.

Comet Hartley 2 is a small comet, measuring just under 1.5 kilometers across. But it is very active, researchers said, emitting lots of dust and vapor when it nears the sun and warms up — which is happening now.

Deep Impact has been eyeing the comet since Sept. 5, when it took its first photo of the icy wanderer from about 60 million kilometers away. Since that date, the spacecraft’s instruments — two telescopes with digital color cameras and an infrared spectrometer — have been gathering loads of data on the target comet.

Deep Impact has been beaming about 2,000 images of the comet back to Earth every day since Oct. 1, researchers said.

This is not Deep Impact’s first comet encounter. The spacecraft served as the mothership for NASA’s Deep Impact mission, which intentionally crashed a probe into Comet Tempel 1 in 2005 to study the object’s composition.

Now, the Deep Impact spacecraft is being put to other uses — it’s tracking and studying various celestial objects under the umbrella of NASA’s broad EPOXI mission. The name is derived from the mission’s dual science investigations — the Extrasolar Planet Observation and Characterization (EPOCh) and Deep Impact Extended Investigations (DIXI).

The spacecraft has covered about 5.2 billion kilometers in the last five years, researchers said, but it’s still going strong, closing in on Comet Hartley 2 at speeds of about 43,500 kilometers per hour.