Catching a Comet! It's been 10 years since the flyby of Comet Hartley 2

Catching a Comet! It's been 10 years since the flyby of Comet Hartley 2
By Jim Pedderson 12/16/2020
While NASA’s OSIRIS-REx recently received much-deserved attention for landing on an asteroid and collecting samples, this wasn’t the first time NASA studied rapidly moving celestial objects. November marked the 10th anniversary of NASA flying the Deep Impact spacecraft, built by Ball Aerospace, to within 700 kilometers (434 miles) of Comet Hartley 2 to make observations and collect images.

A couple of things made this mission, known as EPOXI, unique. It was one of just five times in modern space exploration that a spacecraft was flown to within 700 km of a comet for capturing images.

It was also the first time that two separate comets were observed and imaged by the same spacecraft, using the same instruments and same spatial resolution. EPOXI was a follow-on mission to Deep Impact, which NASA launched in 2005 to not only fly close to Comet Tempel 1, but also to release a “smart” impactor that collided with the comet.

What's in a name

Deep Impact and EPOXI represent a great example of how NASA maximizes the science it obtains from missions. The resiliency of the Ball-built vehicle allowed it to accomplish the Hartley 2 encounter when it was nearly three years beyond its original design life. It then went on to provide data for an additional three years until contact was lost in September 2013.

In addition to being a second part to Deep Impact, EPOXI itself was a two-part mission. The first part of the mission, referred to as EPOCh (Extrasolar Planet Observation and Characterization), involved searching for transiting exo-planets. The second part, known as DIXI (Deep Impact Extended Investigation), involved the now 10-year-old flyby of Comet Hartley 2. The blending of the two missions, EPOCh and DIXI, resulted in the name EPOXI.
Comet Hartley 2
Deep Impact Comet Tempel 1 collision

Deep Impact Provided Deep Dive into Comets

The EPOXI and Deep Impact missions provided scientists with extremely valuable data on the nature of comets.

“The ability to capture images from so close allowed us to see that Hartley 2 was vastly different than Tempel 1,” noted Amy Walsh, who served as Command and Data Handling Lead on the 16-member EPOXI mission team for Ball Aerospace. “It had a different shape, different surface features, and was significantly more active, spewing basketball-sized chunks of material in its wake. The first images wowed all of us.”

Just five years earlier, the Impactor spacecraft released from Deep Impact collided with Tempel 1 at closing speeds of 23,000 mph. The Impactor’s onboard camera relayed close-up images of the comet’s surface and the Flyby’s onboard instruments collected images and spectra of excavated material from the nucleus of the comet, giving scientists an unprecedented view of the characteristics of comets and the materials inside.

Deep Impact and EPOXI were also instrumental in discoveries outside of their mission parameters. In 2009, during flybys of the Earth and Moon to get gravity boosts necessary for traveling to its rendezvous with Hartley 2, the instruments aboard Deep Impact were used to make lunar observations and provided the first clear evidence that water exists on the surface of the Moon.

Getting into space is just half the battle

As the mission prime contractor, Ball Aerospace was responsible for building the Flyby and Impactor spacecraft, as well as the cameras and imagers. Ball also conducted the environmental testing and provided launch and mission support.

“We had a great mix of veterans and newcomers to the team that made flying the spacecraft look easy,” recalled Walsh, whose EPOXI team received a NASA Group Achievement Award in 2009 for its outstanding contributions to the NASA mission.

Deep Impact Flyby Spacecraft
Deep Impact Flyby Spacecraft
The success of the multi-faceted EPOXI-Deep Impact mission has the potential to inspire future programs. It exemplifies Ball’s heritage, capabilities and commitment to science at any scale, from developing technology to measure methane emissions on Earth to building spacecraft and instruments for observing the deepest reaches of space. Ball Aerospace has played a role in some of the most notable planetary science missions of the modern era, including the Hubble Space Telescope and the Kepler/K2 mission.

Next year, the Ball-built optical technology and the iconic honeycomb mirror system of the James Webb Space Telescope is scheduled to launch on its one-million-mile journey to detect the light from the first galaxies ever formed and explore planets around distant stars.
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