Second life: comet mission continues

Comet Hartley 2 seen by the EPOXI mission

The first view of Comet Hartley 2 (fuzz ball in the centre of the image) taken by the EPOXI mission, which is using NASA's Deep Impact spacecraft to study the comet in great detail. The rendezvous date will be November 4, 2010.

On Sunday, September 5, NASA’s Deep Impact spacecraft beamed down the first of more than 64,000 images it’s expected to take of Comet Hartley 2. The spacecraft, now on an extended mission known as EPOXI, has an appointment with the comet on November 4, 2010.

Deep Impact made headlines around the world in July 2005 when it conducted a fly-by of Comet Tempel 1 and fired a projectile into it. The projectile caused a huge explosion on impact and gouged out a huge chunk of the Temple 1’s surface and sub-surface ice, enabling Deep Impact’s instruments to give us our first view of the ice that lives below the surface of a comet.

Impact on comet Tempel 1

Flash back to 2005, when Deep Impact fired a projectile into Comet Tempel 1, causing a huge explosion that gave scientists their first look at the interior of a comet.

It was realised soon after that the Deep Impact spacecraft was still in good shape, and could be retargeted to take an up close look at a second comet, Hartley 2.

There won’t be any fireworks this time, though, as Deep Impact’s only projectile was destroyed in its deliberate 2005 collision with comet Tempel 1.

Instead, it will use all three of its instruments (two telescopes with digital colour cameras and an infrared spectrometer) to scrutinise Hartley 2 for more than two months.

The spacecraft is stilled called Deep Impact, but the mission has been renamed EPOXI…a combination of the names for the two new mission aims: the extrasolar planet observations, called Extrasolar Planet Observations and Characterisation (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI).

Longest up-close views of a comet

“Like any tourist who can’t wait to get to a destination, we have already begun taking pictures of our comet…Hartley 2,” said Tim Larson, the project manager for EPOXI from NASA’s Jet Propulsion Laboratory.

“We have to wait for November 4 to get the close-up pictures of the cometary nucleus, but these approach images should keep the science team busy for quite some time as well.”

Deep Impact spacecraft

Artist's impression of the Deep Impact spacecraft.

The imaging campaign, along with data from all the instruments aboard Deep Impact, will afford the mission’s science team the best, extended view of a comet in history during Hartley 2’s pass through the inner Solar System.

With the exception of one, six-day break to calibrate instruments and perform a trajectory correction manoeuvre, the spacecraft will continuously monitor Hartley 2’s gas and dust output for the next 79 days.

This first image of comet Hartley 2 taken by Deep Impact was obtained by the spacecraft’s Medium Resolution Imager on September 5 when the spacecraft was 60 million kilometres (37.2 million miles) from the comet.

EPOXI is an extended mission that utilises the already “in flight” Deep Impact spacecraft to explore distinct targets of opportunity.

Adapted from information issued by NASA / JPL / University of Maryland.

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